Inheritance

7(a)(i) R – (sister) chromatids ; 2 S – centromere ; 7(a)(ii) any three from: 3 1 have same genes ; R same number of genes 2 (genes at) same, loci / position on a chromosome ; 3 same position of, S / centromere ; 4 same length ; 5 forms bivalent ; © UCLES 2021 Page 15 of 22 7(a)(iii) 2 G g G g top 3 different H h H h ; on each pair I i I i J J j j S S all same K K k k ; on each pair L L l l M M m m 7(b) prophase 1 ; 1 © UCLES 2021 Page 16 of 22 7(c) any three from: 3 1 homologous chromosomes / bivalents, align independently of each other ; 2 at the, equator / metaphase plate ; 3 idea that this leads to different combinations of chromosomes in the daughter cells ; 4 results in new combinations of alleles ; 5 AVP ; e.g. in humans 223 / 2n, different combinations Question Answer Marks

7(a) codominant 3 1 both (alleles), affect / seen in / expressed in / contribute to (phenotype) ; 2 in heterozygote ; recessive 3 affects / seen in / expressed / contributes to, (phenotype) (only) when dominant (allele) absent / in homozygote ; 7(b) 3 parental phenotype A B parental genotype IA Io IB Io gametes IA Io IB Io ; offspring genotype IA IB IA Io IB IO Io Io ; offspring phenotype AB A B O ; 7(c) any three from: 3 1 males / men / boys, are, XY / have (only) one X chromosome ; 2 man / father, passes Y to, male offspring / son ; 3 man / father, does not pass X to, ♂ offspring / son ; 4 man / father, passes, X / mutation, to, female offspring / daughter ; 5 woman / mother, passes X / mutation, to, male offspring / son ; © UCLES 2021 Page 12 of 16

7(a) allele – variety / form, of a gene ; 2 dominant –(allele) always expressed / always has effect on the phenotype / expressed in heterozygote / has effect on the phenotype of heterozygote ; © UCLES 2021 Page 15 of 22 7(b)(i) 5 double homozygous wild type parent recessive parent parental red eye, long wing purple eye, vestigial wing ; phenotype parental RrNn rrnn ; genotype offspring offspring red eye, purple eye, red eye, purple eye, ; phenotype long wing vestigial wing vestigial wing long wing offspring RrNn rrnn Rrnn rrNn ;; genotype numbers of 1339 1195 151 154 offspring offspring genotypes – 4 correct = 2 marks, 3 correct = 1 mark allow short wing for vestigial wing allow alleles in any order in genotypes ignore brackets and circles around alleles © UCLES 2021 Page 16 of 22 7(b)(ii) any three from: 3 1 (two) genes are linked / autosomal linkage or alleles inherited together ; 2 no, independent / random, assortment ; 3 large numbers of parental type offspring / small numbers of recombinant offspring ; 4 recombinants due to crossing over ; 5 during, meiosis / prophase 1 / gamete formation ; Question Answer Marks

10(a) any nine from: 9 gene mutation 1 base substitution ; 2 (often) does not have a significant effect on phenotype / silent mutation ; 3 base, insertion / deletion leads to, frame shift / described ; 4 (so) has significant effect on phenotype ; 5 change in, primary structure / amino acid sequence / polypeptide made ; 6 change in, tertiary structure / 3D shape / folding ; 7 loss of function in protein or enzyme / example described ; 8 (premature) stop codon ; Huntinton’s disease 9 (mutant allele) is dominant ; 10 HD / dominant, allele has more repeats of base triplet CAG (than normal) ; 11 heterozygote will have disease ; 12 brain cells die more rapidly (than normal) / brain degeneration ; 13 involuntary movements / mental deterioration or described / mood changes ; 14 onset in middle age / idea that no change in phenotype in earlier life ; 15 AVP ; e.g. greater number of CAG repeats affects, earlier onset / severity of disease © UCLES 2021 Page 21 of 22 10(b) any six from: 6 1 DELLA proteins inhibit, transcription factor / PIF; 2 gibberellin binds to receptor ; 3 in aleurone layer ; 4 ref. to enzyme involved ; 5 DELLA proteins broken down ; 6 TF / PIF, binds to promoter region (of DNA) ; 7 transcription of gene coding for amylase / AW ; 8 ref. to translation (leading to amylase production) ; © UCLES 2021 Page 22 of 22

7(a) any four from: 4 1 haemoglobin less soluble ; 2 (if oxygen concentration decreases) haemoglobin molecules, stick together / form long fibres ; 3 red blood cells, pulled out of shape / become sickle shaped ; 4 blood poor at transporting oxygen ; 5 (so) less oxygen getting to, cells / tissues / organs ; 6 red blood cells may, get stuck in / block, capillaries / vessels ; 7 pain / sickle cell crisis / fatigue ; 7(b)(i) both alleles, contribute to / expressed in, the phenotype (in the heterozygote) ; 1 7(b)(ii) any one from: 1 smaller quantity of abnormal haemoglobin ; fewer red blood cells become sickled / sickling less severe ; ORA not affected by low(er) oxygen concentration ; © UCLES 2021 Page 16 of 22 7(b)(iii) parental SCT SCT 3 phenotype parental HbA HbS HbA HbS ; genotype gametes HbA HbS HbA HbS offspring HbA HbA HbA HbS (HbA HbS) HbSHbS ; genotypes offspring normal SCT (SCT) SCA ; phenotypes I carrier © UCLES 2021 Page 17 of 22

7(a) any four from: 4 1 base / nucleotide, insertion / deletion / substitution ; 2 frameshift / changed reading frame ; 3 ref. to stop codon ; 4 changes / different, primary structure / amino acid sequence ; 5 changes / different, folding / 3D shape / 3o structure, of enzyme / protein ; 6 active site does not, bind / fit, substrate / complex molecules ; © UCLES 2021 Page 15 of 21 7(b) 1 key e.g. H = normal (allele) h = Hunter (syndrome allele) ; 5 parental normal male normal female phenotype 2 parental XHY XH Xh ; genotype gametes ( XH Y XH Xh ) 3 offspring XH XH XH Xh XH Y Xh Y ; genotypes 4 offspring normal normal / carrier normal Hunter S ; phenotypes female female male male 5 probability 0.25 / 25% / 1 in 4 ; © UCLES 2021 Page 16 of 21

7(a) any two from: 2 1 tyrosine converted to, DOPA / dopaquinone ; 2 dopaquinone converted to melanin ; 3 ref. to melanocytes ; 7(b)(i) parental (black x yellow) 6 phenotype parental BbEe x Bbee ; genotype gametes BE Be bE be Be be ; offspring genotypes ;; BBEe BbEe BbEe BBee Bbee Bbee bbee bbEe offspring phenotypes ; black black black yellow yellow yellow yellow brown ratio 3 black : 1 brown : 4 yellow ; ecf to max 3 7(b)(ii) transcription factor ; 1 © UCLES 2021 Page 19 of 24

7(a) any four from: 4 1 base / nucleotide, insertion / deletion / substitution ; 2 frameshift / changed reading frame ; 3 ref. to stop codon ; 4 changes / different, primary structure / amino acid sequence ; 5 changes / different, folding / 3D shape / 3o structure, of enzyme / protein ; 6 active site does not, bind / fit, substrate / complex molecules ; © UCLES 2021 Page 15 of 21 7(b) 1 key e.g. H = normal (allele) h = Hunter (syndrome allele) ; 5 parental normal male normal female phenotype 2 parental XHY XH Xh ; genotype gametes ( XH Y XH Xh ) 3 offspring XH XH XH Xh XH Y Xh Y ; genotypes 4 offspring normal normal / carrier normal Hunter S ; phenotypes female female male male 5 probability 0.25 / 25% / 1 in 4 ; © UCLES 2021 Page 16 of 21

4(a)(i) label line to where white chromatid crosses over grey chromatid ; 1 4(a)(ii) any four from: 4 1 (crossing over is) between non-sister chromatids ; 2 (non-sister chromatids have) different combinations of alleles ; 3 exchange alleles ; 4 (chromatids have) new combinations of alleles ; 5 linkage groups broken ; 6 idea that gametes have unique combination of alleles ; 7 random fusion of gametes (during fertilisation) ; 4(b)(i) any two from: 2 1 (first) generation of offspring (from parental cross) ; 2 (parents are) homozygous / true bred / pure bred / pure breeding ; 3 F1 generation will be heterozygous ; © UCLES 2022 Page 12 of 22 4(b)(ii) 3 expected (𝑂−𝐸)(cid:2870) phenotype O E O – E (O – E)2 ratio 𝐸 full band and 9 99 76.5 22.5 506.25 6.62 rays full band and 3 21 25.5 –4.5 20.25 0.79 no rays broken band and 3 8 25.5 –17.5 306.25 12.01 rays broken band and 1 8 8.5 –0.5 0.25 0.03 no rays 1 mark for E and O – E correct ; (𝑂−𝐸)2 1 mark for (O – E)2 and correct ; 𝐸 χ2 = 19.45 ; ecf for 1 mistake in one box © UCLES 2022 Page 13 of 22 4(b)(iii) any three from: 3 1 19.45 / chi-squared value, is greater than, 7.81 / critical value (at p = 0.05) ; 2 results are / observed ratio is, significantly different to expected ratio ; 3 so differences are not due to chance ; 4 due to, increase in full band phenotypes / decrease in broken band phenotypes ; 4(b)(iv) any two from: 2 1 epistasis ; 2 linkage ; 3 lethal allele ; 4 chance deviations ; 5 environmental effects ; 6 mutations ; 7 small sample size ; © UCLES 2022 Page 14 of 22

7(a) gene 2 length of DNA coding for a polypeptide ; allele alternative / different, form / version, of a gene ; 7(b) parents phenotypes red eyes apricot eyes 3 parents genotypes CRCH CACW gametes ( CR CH CA CW ) offspring genotypes CRCA CRCW CHCA CHCW ; offspring phenotypes red eyes (red eyes) apricot eyes honey eyes ; ratio 2 : 1 : 1 ; 7(c) 1 cross with, white-eyed fly / CWCW ; 3 any two from: 2 if all red-eyed then CRCR ; 3 if (some red-eyed and) some apricot-eyed then CRCA ; 4 if (some red-eyed and) some honey-eyed then CRCH ; 5 if (some red-eyed and) some white-eyed then CRCW ; © UCLES 2022 Page 14 of 19

1(a)(i) DOPA / dopaquinone / melanin ; 1 1(a)(ii) cyclic AMP / cAMP ; A calcium ions 1 1(a)(iii) any two from: 2 1 albino / albinism ; 2 no pigment or melanin in skin / pale skin or white hair ; Ignore fair, skin / hair 3 red / pink, eyes / irises ; A blue 4 poor vision / described or eyes sensitive to light or jerky eye movements ; Ignore blindness 1(b) symbols ; e.g. B allele for black fur 4 b allele for (light) brown fur parental genotypes Bb x Bb ; gametes B b B b offspring genotypes BB Bb (Bb) bb ; offspring phenotypes black black (black) (light) brown ; accept gametes mark from a Punnett square © UCLES 2022 Page 5 of 22

7(a) RNA polymerase attached to promoter ; 2 repressor detached from operator ; 7(b)(i) structural (gene) ; 1 7(b)(ii) lactose permease ; A beta-galactoside permease 2 movement / transport, of lactose into cell or makes (cell surface) membrane (more) permeable to lactose ; 7(c) 1 population increases, then levels off, increases, then levels off / AW ; 4 any three from: 2 (first increase) glucose, metabolised / respiration ; 3 (first levelling off) glucose has run out ; 4 (first levelling off) lactose, hydrolysed / broken down, into, glucose / galactose ; 5 (second increase) glucose / galactose, metabolised / respired ; 6 (second levelling off) lactose / glucose / galactose, has run out ; 7 AVP ; e.g. idea of time delay (for, lactose permease / beta galactosidase, to work) © UCLES 2022 Page 17 of 22

7(a) gene – a length of DNA / a sequence of DNA nucleotides, that codes for a particular, protein / polypeptide ; 2 locus – the position of a, gene / allele, on a chromosome ; 7(b) parent genotype ( AaBb  AaBb ) 6 parent phenotype brown (brown) ; gametes AB Ab aB ab  ( AB Ab aB ab ) ; AB Ab aB ab AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb ab AaBb Aabb aaBb aabb ;; offspring phenotypes linked to genotypes ; ratio – 9 brown : 3 black : 4 white ; © UCLES 2022 Page 17 of 23 7(c) any three from: 3 1 (base), substitution / deletion / insertion or frame shift ; 2 ref. to change in, primary / secondary / tertiary, structure (of polypeptide / protein) or change in, 3D / active site, shape ; 3 ref. to stop codon ; 4 (so) no / inactive, tyrosinase produced ; 5 tyrosine not converted to, DOPA / dopaquinone ; 6 melanin not formed ; © UCLES 2022 Page 18 of 23

7(a) 1 symbols B / XB = (allele for) black (fur) 5 G / XG = (allele for) ginger (fur) ; parents phenotypes tortoiseshell female ginger male 2 parents genotypes XBXG XGY ; 3 gametes XB XG XG Y ; 4 offspring genotypes XBXG XBY XGXG XGY ; 5 offspring phenotypes tortoiseshell black ginger ginger female male female male ; 7(b) any three from: 3 1 TYR codes for tyrosinase ; 2 converts tyrosine into DOPA ; 3 converts DOPA into dopaquinone ; 4 dopaquinone converted to melanin ; Question Answer Marks

6(a)(i) any three from: 3 1 trp operon regulatory gene / trpR, codes for an inactive repressor and lac operon regulatory gene / lacI, codes for active repressor ; 2 lac operon does not have an attenuator ; ora 3 lac operon has fewer structural genes or 3 vs 5 structural genes ; 4 lac operon uses, an inducer / (allo)lactose and trp operon uses, a repressor / tryptophan ; 5 (allo)lactose, binds / inactivates, repressor, so repressor, leaves / cannot bind to, operator and tryptophan, binds / activates, repressor, so repressor can bind to operator ; 6 (allo)lactose causes genes to be, transcribed / switched on / expressed and tryptophan causes genes to be not, transcribed / switched on / expressed ; 6(a)(ii) any one from: 1 1 (share) one promoter ; 2 all, enzymes / proteins / products, work together ; 6(a)(iii) structural genes: 2 code for, enzymes / structural proteins / non-regulatory proteins / rRNA / tRNA ; regulatory genes: code for, proteins / products, that control, gene expression / transcription ; A code for, transcription factors / repressor proteins © UCLES 2022 Page 14 of 19 6(a)(iv) any two from: 2 1 end-product inhibition / negative feedback / feedback inhibition ; 2 tryptophan, binds to / activates, repressor or tryptophan allows repressor to bind to operator ; 3 tryptophan, stops / reduces, trpA or gene transcription / trpA or gene expression / protein synthesis / tryptophan synthase being made ; 6(b)(i) any four from: 4 1 (gibberellin) binds to receptor ; 2 ref. enzyme ; 3 (enzyme causes) DELLA breakdown ; 4 DELLA no longer, binds to / inhibits, transcription factor / PIF ; 5 (so) transcription factor / PIF / RNA polymerase, binds to, DNA / promoter ; 6 (growth) genes, switched on / expressed / transcribed ; 6(b)(ii) mark first answer 1 transcription factor(s) ; © UCLES 2022 Page 15 of 19

7(a) dominant – allele always has effect on phenotype / allele expressed in homozygote and heterozygote / allele always 2 expressed ; recessive – allele only has effect on phenotype if dominant allele absent / only expressed in homozygote ; 7(b) symbols ZB = allele for bronze feathers 5 Zb = allele for brown feathers ; parents phenotypes bronze male brown female parents genotypes ZBZb x ZbW ; gametes ZB Zb Zb W ; offspring genotypes ZBZb ZBW ZbZb ZbW ; offspring phenotypes bronze male bronze female brown male brown female; ecf for putting allele on W ecf for incorrect symbols with no superscript ecf for different letters for alleles no sex chromosomes = no marks 7(c) 1 cross with brown female ; 3 2 if all offspring bronze then male is, homozygous / ZBZB ; 3 if (some offspring are bronze and) some are brown then male is, heterozygous / ZBZb ; © UCLES 2022 Page 16 of 19

7(a) 1 symbols B / XB = (allele for) black (fur) 5 G / XG = (allele for) ginger (fur) ; parents phenotypes tortoiseshell female ginger male 2 parents genotypes XBXG XGY ; 3 gametes XB XG XG Y ; 4 offspring genotypes XBXG XBY XGXG XGY ; 5 offspring phenotypes tortoiseshell black ginger ginger female male female male ; 7(b) any three from: 3 1 TYR codes for tyrosinase ; 2 converts tyrosine into DOPA ; 3 converts DOPA into dopaquinone ; 4 dopaquinone converted to melanin ; Question Answer Marks

5(a) 4 stage of meiosis spindle fibres diagram attach to centromeres and arrange homologous pairs of metaphase I chromosomes at the equator of the cell (contract to) pull, anaphase I centromeres / chromosomes, towards poles / to centrioles ; prophase II ; re-form spindle in daughter cells (forming) four daughter cells ; two single chromosomes telophase II disassemble inside a (re-forming) nuclear envelope ; © UCLES 2023 Page 12 of 20 5(b) any four from: 4 1 (meiosis / reduction division) produces gametes ; 2 (two) gametes fuse / fertilisation occurs, to form a zygote ; 3 zygote will have maternal and paternal chromosomes / AW ; 4 gametes, are haploid / are n / have half the normal number (of chromosomes) ; 5 so the zygote, is diploid / 2n ; 6 prevents, doubling of chromosome number / polyploidy / having too many chromosomes or allows chromosome number to remain constant ; Question Answer Marks

6(a)(i) AAbhbh 2 Aabhbh AAbhb Aabhb ; ; © UCLES 2023 Page 12 of 17 6(a)(ii) long, white / albino ; 1 6(b) 1 F1 parent genotypes: AaBb x AaBb ; 5 2 gametes: A A a a A A a a B b B b B b B b ; 3 F2 offspring genotypes: AB Ab aB ab AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb ab AaBb Aabb aaBb aabb ; 4 evidence of deduction of phenotypes from (min 9 different) genotypes ; 5 F2 offspring phenotype ratio: 9 : 3 : 3 : 1 black white black white short short long long ; © UCLES 2023 Page 13 of 17 6(c)(i) any three from: 3 1 because they are, on separate chromosomes / not linked ; 2 each, bivalent / pair of homologous chromosomes, orients itself separately ; 3 (at equator) in metaphase I of meiosis ; 4 gives, four / different / new, combinations of alleles / gametes ; 5 parental allele combinations are not, preserved / fixed ; 6 AVP ; 6(c)(ii) 1 phenotype obser ved expected (OE)2 numb number (O – E)2 E er (E) (O) short, black fur 25 27 4 0.148 long, black fur 11 9 4 0.444 short, white fur 8 9 1 0.111 long, white long 4 3 ; 1 0.333 6(c)(iii) 1.036 ; 1 © UCLES 2023 Page 14 of 17

8 any four from: 4 1 DNA / chromatin / chromosomes / chromatids, condense ; 2 homologous chromosomes, pair up / undergo synapsis / form bivalents / form tetrads ; 3 crossing-over ; 4 between non-sister chromatids ; 5 detail of crossing over ; 6 chromosomes (stay) joined at, cross-over points / chiasmata ; Question Answer Marks

10 any six from: 6 1 le allele codes for a, non / less, functional enzyme ; 2 3 beta-hydroxylase ; 3 alanine replaced with threonine at active site ; 4 inactive gibberellin / GA20, not converted to, active gibberellin / GA1 ; 5 no / less, gibberellin to bind to, (intracellular) receptor / GID1 ; 6 no / less, gibberellin-receptor-DELLA complexes formed ; 7 DELLA not broken down ; 8 DELLA (stays) bound to, transcription factors / PIF ; 9 transcription factor / PIF / RNA polymerase, cannot, bind to promoter ; 10 growth genes / XET gene, (stay) switched off / not transcribed / not expressed ; 11 stem does not elongate / internode length is small OR no / less, cell division in stem ; © UCLES 2023 Page 17 of 17

2(a) haploid is one (complete) set of chromosomes ; 2 diploid is two (complete) sets of chromosomes ; if only comparative statement = max 1 e.g. haploid is n chromosomes and diploid is 2n haploid is half the number of chromosomes as diploid / AW 2(b) prophase I 4 chromosomes / chromatin, condense / shorten / fatten I DNA or homologous chromosomes pair up / bivalents form or crossing over / synapsis / chiasmata formation ; metaphase I homologous (pairs of) chromosomes / bivalents, line up on the, equator / metaphase plate or random / independent, assortment, of homologous (pairs of) chromosomes / bivalents ; anaphase I chromosome(s) / one of each pair of chromosomes, moves (to pole / end of cell) ; telophase I chromosomes reach the opposite, poles / centrosomes / centrioles / end of cell or chromosomes decondense / chromatin formation / chromosomes become diffuse ; 2(c) cytokinesis ; 1 © UCLES 2023 Page 9 of 25

5(a) 3 (OE)2 phenotype observed expected O – E (O – E)2 E red with black spots 279 281.25 –2.25 5.0625 0.018 white with black spots 95 93.75 1.25 1.5625 0.017 red 96 93.75 2.25 5.0625 0.054 white 30 31.25 –1.25 ; 1.5625 ; 0.05(0) 0.139 / 0.14 ; one mark for each column 5(b) any two from: 2 accept null hypothesis (no mark) 1 2 value / 0.139 / 0.14, is lower than, the critical value / 7.815 ; 2 the observed numbers are not significantly different to the expected numbers (at p = 0.05) ; 3 any differences are due to chance ; allow ecf from 5(a) © UCLES 2023 Page 13 of 24 5(c) 4 female gametes male XRB XrB XRb Xrb gametes XRXrBB XrXrBB XRXrBb XrXrBb female female female female XrB red + black white + black red + black white + black spots spots spots spots XRYRBB XrYRBB XRYRBb XrYRBb male male male male YRB red + black red + black red + black red + black spots spots spots spots XRXrBb XrXrBb XRXrbb XrXrbb female female female female Xrb red + black white + black white + no red + no spots spots spots spots XRYRBb XrYRBb XRYRbb XrYRbb male male male male YRb red + black red + black red + no spots red + no spots spots spots ;;;; © UCLES 2023 Page 14 of 24 5(d) mark as pairs 2 1 allele R / dominant red allele, is on Y chromosome ; 2 (so all) males inherit, dominant red allele / allele R or only YR is present in the gametes ; 3 no, allele r / recessive white allele, on Y chromosome or allele r only exists on the X chromosome ; 4 (so) males never inherit, recessive white allele / allele r ; 5(e) any two from: 2 1 mutation ; 2 detail of mutation ; 3 crossing over ; 4 (of) the R allele / dominant red allele, from a Y chromosome to an X chromosome ; Question Answer Marks

6(a)(i) any two from: 2 1 transparent phenotype (reappears) in F2 (but not F1) ; 2 so it is, inherited / passed down / genetic / not environmental ; 3 new / recessive, allele ; 6(a)(ii) 9 : 3 : 3 : 1 ; 1 © UCLES 2023 Page 11 of 16 6(a)(iii) any four from: 4 1 two genes ; 2 on separate chromosomes / not linked ; 3 not sex-linked / autosomal ; 4 each gene has / both genes have, two alleles ; 5 albino / white stripes, is recessive (allele) ; 6 transparent / non-gold, is recessive (allele) ; 7 wild type is dominant for both genes ; 6(b) any four from: 4 1 homologous chromosomes, pair up / form bivalents ; 2 at prophase I ; 3 independent assortment / random orientation or independent segregation ; 4 (happens) at metaphase I or at anaphase I ; 5 one chromosome of (each) pair has dominant allele and one has recessive ; 6 four, combinations / permutations / different gametes ; 7 worked example / diagram ; © UCLES 2023 Page 12 of 16

2(a) involve mitosis: 1 / 3 ; 5 involve meiosis: 4 ; produces new genetic variation: 2 / 4 ; shows only haploid cells: 1 / 5 ; ignore 2 shows only diploid cells: 3 ; ignore 2 © UCLES 2023 Page 7 of 18 2(b) any four from: 4 1 genetic variation ; 2 due to, crossing over / independent assortment ; 3 some will, be adapted (to changing environment) / survive or avoids whole population being wiped out / ora ; 4 (allows) stage 1 / stage 3 / asexual reproduction ; 5 (allows) random, mating / fertilisation / fusion of gametes ; 6 some have advantageous combinations of alleles ; 7 AVP ; e.g. ref. to dormancy 2(c) any three from: 3 haploid 1 only cell with harmful mutation will, be affected / die ; 2 rest of population unaffected / AW ; diploid 3 recessive allele for harmful mutation, will be masked by dominant (normal) allele / not expressed in heterozygote ; 4 AVP ; e.g. (haploid) removes mutated allele from population 2(d) any two from: 2 1 eukaryotic (cells) / described ; 2 heterotrophic / saprotrophic / parasitic / described ; 3 chitin cell walls ; 4 (most have) hyphae / mycelium ; 5 multinucleate (cells) ; 6 multicellular and unicellular ; © UCLES 2023 Page 8 of 18

5(a) all correct (1827) ; 1 phenotype observed expected number number brown body colour, straight wings 2843 1827 brown body colour, curved wings 855 1827 black body colour, straight wings 842 1827 black body colour, curved wins 2768 1827 5(b) any four from: 4 1 ref. to 3 degrees of freedom ; 2 the, 2 value / 2098, is greater than 7.815 (at p=0.05) ; 3 there is a significant difference ; 4 reject the null hypothesis ; 5 any difference is not due to chance / less than 5% (probability) that difference is due to chance ; 6 the, 2 value / 2098, is greater than, 11.345 at p=0.01 / 16.266 at p=0.001 or less than, 1% / 0.1% (probability), that difference is due to chance ; © UCLES 2023 Page 11 of 18 5(c) any four from: 4 1 greater numbers of parental phenotypes / fewer numbers of recombinants ; 2 genes are linked / autosomal linkage / genes are on same chromosome ; 3 alleles inherited together ; 4 B inherited with D and b inherited with d or B and D in the same gamete and b and d in the same gamete ; 5 no independent assortment ; 6 crossing over (produces recombinants) ; 7 during, meiosis / prophase I / gamete formation ; 8 AVP ; e.g. idea that genes are far enough apart on chromosome for recombination to occur Question Answer Marks

6(a)(i) any two from: 2 1 transparent phenotype (reappears) in F2 (but not F1) ; 2 so it is, inherited / passed down / genetic / not environmental ; 3 new / recessive, allele ; 6(a)(ii) 9 : 3 : 3 : 1 ; 1 © UCLES 2023 Page 11 of 16 6(a)(iii) any four from: 4 1 two genes ; 2 on separate chromosomes / not linked ; 3 not sex-linked / autosomal ; 4 each gene has / both genes have, two alleles ; 5 albino / white stripes, is recessive (allele) ; 6 transparent / non-gold, is recessive (allele) ; 7 wild type is dominant for both genes ; 6(b) any four from: 4 1 homologous chromosomes, pair up / form bivalents ; 2 at prophase I ; 3 independent assortment / random orientation or independent segregation ; 4 (happens) at metaphase I or at anaphase I ; 5 one chromosome of (each) pair has dominant allele and one has recessive ; 6 four, combinations / permutations / different gametes ; 7 worked example / diagram ; © UCLES 2023 Page 12 of 16

2(a) any four from: 4 1 test cross ; 2 cross (tall plant) with dwarf plant ; 3 (dwarf plant must be) le le / homozygous recessive ; 4 if all offspring are tall then parent plant is, Le Le / homozygous dominant ; 5 if offspring are 1:1 tall:dwarf / if any offspring are dwarf, then parent plant is, Le le / heterozygous ; 6 AVP ; e.g. detail of breeding experiment cross pollination, seed harvesting, seed germination 2(b)(i) hormone / cell signalling (molecule) ; A ligand / plant growth regulator 1 2(b)(ii) 1 (causes) cell elongation ; A increases cell, division / mitosis 2 2 idea that plant / stem, grows taller ; Question Answer Marks

3(a) 1 both alleles of a, gene / genotype, are the same ; 2 2 phenotype / effect, of (recessive) allele is masked by a dominant allele or two copies of the (recessive) allele are needed for phenotype to be displayed or alleles only affect the phenotype in the absence of a dominant allele or (genotype) must be homozygous for the (recessive) allele to affect the phenotype ; © Cambridge University Press & Assessment 2024 Page 6 of 21 3(b)(i) number of heterozygous people = 1 680 000 ; ; ; 3 must be to 3 significant figures or more A 1 675 000 to 1 685 000 ; ; ; R 1 700 000 max 2 if decimal places in final answer allow max 2 for working if final answer incorrect (q = √10 800 / 67 100 000 or √0.000161 or 0.0127) p = 1 – 0.0127 or 0.987 (2pq = 2  0.9873  0.0127 or 0.0251) calculation for number of heterozygous people = 67 100 000  0.0251 or 2pq 3(b)(ii) any three from: 3 1 ref. natural selection ; 2 selection pressure against cystic fibrosis (CF) ; 3 (people with) CF do not survive as long / AW ; 4 heterozygotes are calculated from a smaller CF population / AW ; 5 (some) people with CF who have died will have passed on CF allele ; © Cambridge University Press & Assessment 2024 Page 7 of 21 3(c)(i) any three from: 3 1 (median) predicted life expectancy increased (over time) ; 2 data quote ; e.g. from 2008 to 2020 increase from 38.8 to 50.6 years increase of 11.8 % increase of 30.4 3 treatment can be started early ; 4 better treatment / improved care (between 2008 and 2020) ; 3(c)(ii) any three from: 3 1 reduces worry / AW, if result is negative ; ora 2 can make informed reproductive decisions / AW ; 3 cost / availability, of test ; 4 plan for care of child with CF ; 5 idea of further genetic testing ; e.g. counselling / testing of embryo / testing of partners 6 idea that test is not 100% accurate ; 7 problems related to, stigma / discrimination / insurance / confidentiality ; © Cambridge University Press & Assessment 2024 Page 8 of 21

6(a)(i) any one from: 1 1 same / equal, size / length ; 2 same, shape / position of centromere ; 3 same banding pattern ; 6(a)(ii) any three from: 3 1 recessive / mutation = faulty / inactive / no, tyrosinase ; 2 (melanocytes) do not produce, melanin / pigment ; 3 ref. to skin / hair / iris ; 4 AVP ; © Cambridge University Press & Assessment 2024 Page 10 of 15 6(b) gametes (on Punnett square) 4 1 BF Bf bF bf ; Punnett square BF Bf bF bf BBFF BBFf BbFF BbFf BF black black black black BBFf BBff BbFf Bbff Bf black white black white BbFF BbFf bbFF bbFf bF black black brown brown BbFf Bbff bbFf bbff bf black white brown white 2 correct offspring genotypes on Punnett square ; 3 phenotypes matching genotypes ; offspring phenotype ratio 4 9 black : 3 brown : 4 white ; Question Answer Marks

9(a) any two from: 2 discontinuous continuous (forms / phenotypes / categories) (forms / phenotypes / categories) not distinct / not distinct / discrete / categoric / do not overlap / do not form discrete / overlap / form a (gradual) range / include a (gradual) range / no intermediates / two or few intermediates / many different forms / many values on a different forms spectrum ; not a normal distribution / few bars (on bar chart) normal distribution or normal / bell-shaped curve (on graph) ; no / little, effect from environment some / large, effect from environment ; A genes only 9(b) any two from: 2 1 one / two, genes (control colour pattern) ; 2 different alleles of a gene have a large effect ; 3 multiple / three, alleles ; 4 gene interaction / epistasis ; 5 AVP ; 9(c) any two from: 2 1 temperature / food (supply) ; 2 of larva / during larval development ; 3 egg size / diet of mother / size of mother ; © Cambridge University Press & Assessment 2024 Page 14 of 15

3(a) (gene L has) four alleles / LV, LT, LR and Lr ; 1 A a gene which has more than two alleles 3(b) parental genotypes: LT LR x LT LR 4 gametes: LT LR LT LR ; offspring genotypes: LT LT LT LR (LT LR) LR LR ; offspring phenotypes: dfm-a dfm-b (dfm-b) rufipennis ; linked to genotypes ratio of offspring phenotypes: 1 : 2 : 1 ; accept correct phenotype descriptions 3(c) LT and LR ; 2 LT and LR > LV > Lr ; 3(d)(i) (female) LV Lr and (male) Lr Lr ; 2 LV Lr (and LV Lr) ; 3(d)(ii) there are similar numbers of male and female offspring produced 1 (for each phenotype) or female metallic offspring are produced or if linked to X chromosome no female metallic offspring are produced ; 3(d)(iii) chi-squared test ; A 2 1 © Cambridge University Press & Assessment 2024 Page 8 of 20

4(a) any five from: 5 1 a gene codes for a protein which determines the phenotype ; 2 F8 gene ; 3 located on X chromosome / sex-linked ; 4 ref. to recessive allele ; 5 non-functioning factor VIII (protein) or less factor VIII (protein) or no factor VIII (protein) ; 6 (so) blood does not clot quickly enough / excessive bleeding occurs (after an injury) ; 7 link the phenotype to the genotype ; e.g. XF XF = normal female XF Xf = normal female Xf Xf = affected female XF Y = normal male Xf Y = affected male 8 AVP ; e.g. prevents activation of thrombin / fibrinogen not converted to fibrin / ref. to mostly males affected / different mutations cause a range of severity of haemophilia © Cambridge University Press & Assessment 2024 Page 9 of 20 4(b) any three from: 3 1 lele is, homozygous recessive / two recessive alleles ; 2 le (allele) / lele, codes for a non-functional enzyme ; 3 no, active gibberellin / GA 1 or ref. to gibberellin inactive ; 4 no / less, cell elongation or no / less, stem elongation / increase in internodal length ; 5 AVP ; e.g. ref. to GA 3β-hydroxylase / GA3-oxidase / last enzyme in the pathway that produces, active gibberellin / GA 1 le allele codes for alanine instead of threonine (in the enzyme) 4(c) any three from: 3 1 (DELLA proteins) bind to, PIF / transcription factor ; 2 PIF / transcription factor, cannot bind to, DNA / promoter ; 3 RNA polymerase cannot bind to promoter ; 4 no transcription / mRNA not made ; © Cambridge University Press & Assessment 2024 Page 10 of 20

2(a) 3 description of phenotypic variation cause of variation Tomato plants grown in a glasshouse and grown outside V + V G E vary in the yield of tomatoes they produce. Seventeen genes associated with tomato yield have been identified. New strawberry plants from the variety called Sweet Ann are V E made by asexual reproduction. The new plants grow to different sizes and produce different numbers of fruit. The domestic cat has a blood group system with three V G possible blood types: A, B and AB. The blood types are determined by antigens present on the cell surface membrane of red blood cells. Over 50 genes have variants that are associated with V + V G E excessive weight-gain in humans. Other risk factors for excessive weight-gain include diet and exercise. Resting heart rate in humans varies between different V + V G E individuals. Some factors that influence resting heart rate include: biological sex, family history of heart disease, number of cigarettes smoked, medication taken. five correct = 3 marks ;;; four or three correct = 2 marks two or one correct = 1 mark 2(b) mutation ; 1 © Cambridge University Press & Assessment 2024 Page 8 of 20 2(c) any three from: 3 1 crossing over ; 2 independent / random, assortment ; 3 random, fusion of gametes / fertilisation ; 4 random mating ;

3(a)(i) Ttdd and TTdd ; 1 3(a)(ii) 13:3 ; 1 3(a)(iii) epistasis ; 1 3(a)(iv) any five from: 5 1 dominant allele / T / D, results in a functional protein ; 2 two recessive alleles / tt / dd, results in a non-functional protein ; 3 T could code for an enzyme ; 4 (so enzyme catalyses) production of, malvidin / pigment ; 5 D could code for an inhibitor ; 6 (inhibitor) binds to enzyme (coded for by) gene T/t ; 7 (so) reaction to produce, malvidin / pigment, does not occur ; 8 protein (coded by T / t) could be a transcription factor ; 9 transcription factor allow the production of enzyme (needed in the metabolic pathway) ; 10 protein (coded by D/d) could cause the inhibition of transcription factor ; © Cambridge University Press & Assessment 2024 Page 9 of 20 3(b) any four from: 4 1 located on X chromosome / sex-linked ; 2 ref. to recessive allele ; 3 non-functioning, factor VIII / protein or less, factor VIII / protein or no, factor VIII / protein ; 4 (so) blood does not clot quickly enough / excessive bleeding occurs (after an injury) ; 5 link the phenotype to the genotype ; e.g. XFXF = normal female XFXf= normal female XfXf= affected female XFY = normal male XfY = affected male 6 AVP ; e.g. prevents activation of thrombin / fibrinogen not converted to fibrin / ref. to mostly males affected /different mutations cause a range of severity of haemophilia

5(a) any two from: 2 1 one / single, set of chromosomes ; 2 have n (number of) chromosomes / half of diploid number ; 3 chromosomes not in homologous pairs / only one of each homologous pair ; 4 each chromosome is different in, size / shape / genes / loci ; 5(b) sexual reproduction: B and D ; 3 mitosis: two from A, B, C, D ; meiosis: D ; 5(c) any three from: 3 1 to maintain, chromosome / diploid, number ; 2 from parents to offspring / from generation to generation ; 3 to give genetic variation in, gametes / offspring / horses ; 4 too many / extra, sets of chromosomes cause (named) problems ; Question Answer Marks

10(a) (melanic x melanic) 3 Aa x Aa (Gametes) A a and A a ; (Offspring) AA Aa Aa aa ; (melanic, melanic, melanic, typical) (Ratio) 3 melanic : 1 typical ; 10(b) it / (melanic) allele, is dominant ; 1 10(c)(i) melanic / dominant phenotype, is crossed with homozygous recessive ; 1 10(c)(ii) 3 same locus different loci (A / a) (A / a and B / b) genotypes of melanic AA AaBb moths from cross 1 Aa Aabb (aA) ; aaBb ; proportion of test crosses 1 in 3 none / 0 ; (cross 2) giving 100% melanic offspring 10(d) (24  29) ÷ 8 ; 2 = 87 ; © Cambridge University Press & Assessment 2024 Page 15 of 15

4(a) parental genotype Rr x Rr 3 AND gametes R r R r ; offspring genotype RR Rr (Rr) rr ; red red red yellow ; © Cambridge University Press & Assessment 2024 Page 9 of 19 4(b) 1 ratio=9:3:3:1 ; 3 any two from: 2 independent / random, assortment ; 3 of, homologous chromosomes / bivalents / sister chromatids ; 4 stage of meiosis ; e.g. metaphase 1 or metaphase 11 Ignore ref. to crossing over / recombinants Question Answer Marks

5(a) 4 statement discontinuous continuous variation variation often involves one gene only  environmental factors may affect  gene expression there is an additive effect of genes  that contributes to the phenotype there are distinct differences  between the various forms of a ;;;; characteristic 5(b)(i) ref. to spread of results about the mean ; 1 © Cambridge University Press & Assessment 2024 Page 10 of 19 5(b)(ii) t = 4.255 ;;; 3 give 2 marks: if answer is 4.25 or 4.26 if answer is more than 4 significant figures e.g. 4.255439871 if answer is incorrectly rounded to 4 significant figures e.g. 4.256 if answer incorrect then max 2 for working numerator = 4.2 denominator = 0.986972 ecf - if no working mark given then allow one mark for 12.02 as the answer 5(b)(iii) 1 there is a higher (mean) concentration of serum 25-OHD in summer ; ora 3 any two from: 2 value of t / 4.255 > critical value / 3.773 ; 3 there is a significant difference between the two means ; 4 any difference is not due to chance / difference due to chance less than 0.0001% ; ecf from incorrect answer to 5bii 5(b)(iv) genetic AND environmental 1 OR an example of a genetic cause AND an example of an environmental cause ; © Cambridge University Press & Assessment 2024 Page 11 of 19

5(a) any two from: 2 1 one / single, set of chromosomes ; 2 have n (number of) chromosomes / half of diploid number ; 3 chromosomes not in homologous pairs / only one of each homologous pair ; 4 each chromosome is different in, size / shape / genes / loci ; 5(b) sexual reproduction: B and D ; 3 mitosis: two from A, B, C, D ; meiosis: D ; 5(c) any three from: 3 1 to maintain, chromosome / diploid, number ; 2 from parents to offspring / from generation to generation ; 3 to give genetic variation in, gametes / offspring / horses ; 4 too many / extra, sets of chromosomes cause (named) problems ; Question Answer Marks

10(a) (melanic x melanic) 3 Aa x Aa (Gametes) A a and A a ; (Offspring) AA Aa Aa aa ; (melanic, melanic, melanic, typical) (Ratio) 3 melanic : 1 typical ; 10(b) it / (melanic) allele, is dominant ; 1 10(c)(i) melanic / dominant phenotype, is crossed with homozygous recessive ; 1 10(c)(ii) 3 same locus different loci (A / a) (A / a and B / b) genotypes of melanic AA AaBb moths from cross 1 Aa Aabb (aA) ; aaBb ; proportion of test crosses 1 in 3 none / 0 ; (cross 2) giving 100% melanic offspring 10(d) (24  29) ÷ 8 ; 2 = 87 ; © Cambridge University Press & Assessment 2024 Page 15 of 15

4(a) parental gametes H h  H h ; accept from Punnett square 3 offspring genotypes HH Hh Hh hh ; accept from Punnett square offspring phenotypes no disease disease / ; haemochromatosis 4(b) any two from: 2 1 reference to using knowledge of DNA sequence of, HFE gene / C282Y (mutation) ; 2 (from) databases / bioinformatics ; 3 (to) find / identify, the, HFE gene / C282Y (mutation), in fossil DNA sequences ; 4 compare DNA sequence of fossil HFE gene with (sequence for), normal HFE allele / C282Y (mutation) ; 4(c)(i) any four from: 4 1 low, iron / meat, (in diet), acts as a selection pressure ; 2 people, with, C282Y / mutant allele, absorb more iron ; 3 (so), survive / reproduce ; 4 idea that (allele) frequency of mutant allele increased in the population ; 5 natural selection ; 6 (named) heterozygote advantage ; e.g. less likely to be iron deficient / not get haemochromatosis ; 7 AVP ; e.g. C282Y (in heterozygotes) is neutral in present-day diets (so maintained) or gives protection from other diseases © Cambridge University Press & Assessment 2025 Page 10 of 19 4(c)(ii) any three from: 3 1 highest / AW, percentage in Ireland where it first occurred ; 2 higher percentages nearer Ireland due to migration ; ora 3 migration affected by, barriers / borders ; 4 type of diet ; 5 different treatments available (for hereditary haemochromatosis) in different countries ; 6 AVP ; 4(d) any valid difference ; e.g. small database / ethnicity / region / location 1 4(e) 282 ; ; 2 if answer is incorrect allow 1 mark for correctly calculating the number of heterozygotes from incorrect 2pq i.e. 2501  incorrect 2pq © Cambridge University Press & Assessment 2025 Page 11 of 19

5 any five from: 5 1 (meiosis) II ; 2 two cells are visible / four groups of chromosomes ; 3 anaphase ; 4 as two groups of chromosomes per daughter cell ; 5 centromeres / kinetochores, attached to, spindle fibres / microtubules ; 6 spindle fibres / microtubules, shorten / contract ; 7 to pull, (daughter) chromosomes / (sister) chromatids, to opposite poles / described ; 8 the centromeres lead with the chromosome arms following behind / AW ; 9 reference to no nuclear envelope ; Question Answer Marks

3(a)(i) F1 genotypes: AaBb x AaBb ; 5 gametes: AB Ab aB ab (AB Ab aB ab) ; F2 genotypes: AB Ab aB ab AB AABB AABb AaBB AaBb awn awn awn Awn Ab AABb AAbb AaBb Aabb awn awn awn awn aB AaBB AaBb aaBB aaBb awn awn awn awn ab AaBb Aabb aaBb aabb ; awn awn awn no awn F2 phenotypes linked to genotypes (see Punnet Square) ; ratio of F2 phenotypes: 15:1 awn: no awn ; 3(a)(ii) autosomal dominant / epistasis ; 1 I dihybrid © Cambridge University Press & Assessment 2025 Page 11 of 25 3(b) any one from: 1 for seed dispersal ; idea of protection ; anchor into the ground ; obtain more, nutrients / water ; 3(c)(i) any four from: 4 1 artificial selection / selective breeding / humans act as selection pressure ; 2 select (rice) plants / seeds / grains, with no awns ; 3 idea of breeding (selected) plants / self pollination of (selected) plants ; 4 seeds germinate / plants grow / offspring grow ; 5 repeat (selection and breeding) over generations ; 6 AVP ; e.g. ref. to genetic technology detail of pollination © Cambridge University Press & Assessment 2025 Page 12 of 25 3(c)(ii) any three from: 3 1 mutation / change in base sequence, (in An-1) or An-1 not expressed ; 2 transcription factor has different, primary structure / tertiary structure / 3D shape or transcription factor not, produced / functional or transcription factor faulty ; 3 transcription factor does not bind to, the promoter / DNA ; 4 decrease in expression of gene(s) for awn development ; 5 increase in expression of gene(s) for number of grains produced ; Question Answer Marks

4(a) any three from: 3 1 (diploid) cell formed from (two) haploid gametes ; 2 (diploid) cell has two sets of chromosomes / one set of chromosomes from each gamete ; 3 (homologous chromosomes) maternal and paternal chromosomes ; 4 (homologous chromosomes) has same, genes / loci / banding pattern / centromere position / size / length ; 4(b) anaphase 1 / telophase 1 ; 2 separation of, homologous chromosomes / bivalent ; © Cambridge University Press & Assessment 2025 Page 13 of 25 4(c)(i) Fig. 4.1 2 metaphase 2 ; A anaphase 2 Fig. 4.2 telophase 1 ; A anaphase 1 4(c)(ii) 48 ; 1 Question Answer Marks

3(a) 1 enzymes produced when, allolactose / lactose / substrate, is present 2 or enzymes only produced when required ; 2 genes not, expressed / switched on / transcribed, continuously or genes, expressed / switched on / transcribed, when, allolactose / lactose / substrate, binds to repressor ; I inducer 3(b) any seven from: 7 1 lactose enters the bacterium ; 2 lactose binds to the repressor ; 3 causing a shape change ; 4 the repressor detaches from the operator ; 5 promoter unblocked / AW ; 6 RNA polymerase binds to the promoter ; 7 gene(s) transcribed ; 8 β-galactosidase is made ; 9 β-galactosidase breaks down lactose ; galactosidase activity levels off as: 10 β-galactosidase activity at maximum / galactosidase active sites full ; © Cambridge University Press & Assessment 2025 Page 11 of 20

2(a) any two from: 4 gene 1 mutation of, HTT / huntingtin, gene ; 2 ref. to dominant or only one, mutant / AW, allele, needed or heterozygote will have disease ; 3 ref. to (more) CAG repeats ; plus any three from: protein 4 non-functional / AW, huntingtin (protein) ; phenotype 5 idea of cognitive / behavioural / personality / mood, changes ; 6 coordination / movement, difficulties ; 2(b) 1 only males get the disease / females do not get the disease ; 3 2 only males have a Y chromosome / males are XY or females, do not have a Y chromosome / only have (two) X chromosomes ; 3 all, sons / male offspring, of affected, males / fathers, have the disease or all sons will not have the disease if father does not have the disease ; © Cambridge University Press & Assessment 2025 Page 11 of 27 2(c) parental genotypes XAXa x XaY 4 and gametes XA Xa and Xa Y ; correct offspring genotypes XA Xa Xa XA Xa XaXa affected / AW healthy / normal, female female Y XAY XaY affected / AW healthy / normal, male male ; phenotypes linked to genotypes (see Punnet Square) ; ratio of offspring phenotypes: 1 : 1 : 1 : 1 ; © Cambridge University Press & Assessment 2025 Page 12 of 27 2(d) any three from: 3 1 no repressor produced / no repressor binds to operator or altered / faulty, repressor produced ; 2 (so) structural genes are, transcribed / expressed / switched on ; 3 (structural gene) proteins / enzymes, produced ; 4 (these) proteins / enzyme, damage cell / changes metabolism / causes disease ; 5 altered repressor, binds more tightly / AW, to operator ; 6 (so) structural genes, not transcribed / not expressed / switched off ; 7 (structural gene) proteins / enzymes, not produced ; 8 (so) lack of, protein / enzyme, causes, damage to cell / change to metabolism / disease ; © Cambridge University Press & Assessment 2025 Page 13 of 27

1(a)(i) AABB AABb AaBB AaBb ; ; 2 1(a)(ii) long chocolate ; 1 1(b) 4 A A a a A A a a ; B b B b B b B b AB Ab aB Ab AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb Ab AaBb Aabb aaBb aabb ; F2 offspring phenotype number ratio: 9 : 3 : 3 : 1 ; short short long long black chocolate black chocolate ; Mp 4 need phenotypes linked to genotypes by colour, symbol or initials 1(c) 1 structural gene codes for, (named) structural / functional, protein / polypeptide ; 2 2 regulatory gene codes for, transcription factor / repressor protein or regulatory gene, controls / helps / restricts, expression of (other) genes ; © Cambridge University Press & Assessment 2025 Page 8 of 18

2(a)(i) 2 E. turcicum Z. mays 1 chitin cell wall cellulose cell wall structural or or difference no chloroplasts chloroplasts or or hyphae / cells long and branching no hyphae / cells not long and branching or or syncytial / multinucleate / several nuclei per cell one nucleus per cell ; 2 heterotroph(ic) / parasitic / obtain food from host / do autotroph(ic) / phototrophic functional not photosynthesise / photosynthesis(e) ; difference 2(a)(ii) any four from: 4 1 large groups divide into smaller groups ; 2 common / similar / shared, features within a group ; 3 ref. three of: kingdom – phylum – class – order – family ; 4 genus and species = binomial / Linnaean / Latin / scientific, name ; 5 (both in domain) Eukarya ; 6 different kingdoms / Fungi and Plantae ; 2(b)(i) any two from: 2 1 low percentage leaf damage means high resistance (to infection) ; 2 SKV50 = 22% and CML153 = 58% ; 3 SKV50 shows greater resistance (to infection) ; 2(b)(ii) continuous ; 1 © Cambridge University Press & Assessment 2025 Page 9 of 18 2(b)(iii) any four from: 4 1 many / different / several / multiple, genes ; 2 affect, same trait / (percentage) area of leaf damage / resistance ; 3 alleles of, one / each, gene have a small effect ; 4 (different) genes have, additive / combined / interactive, effects ; 5 mathematical treatment to illustrate additive effect ; Question Answer Marks

10 marks from any two groups of mark points to max 6: 6 1 mutant TYR gene codes for non-functioning tyrosinase ; 2 albinism / albino, recessive (disorder / allele) ; 3 lack of melanin / no melanin produced ; 4 giving, pale / fair, skin / hair or giving, transparent / pink, iris ; 5 mutant HBB gene codes for, abnormal (β) globin / haemoglobin S ; 6 sickle cell, anaemia / disease, codominant (disorder / allele) ; 7 less soluble / sticky / rod-forming, haemoglobin makes red blood cells sickle ; 8 sickle cells, block capillaries / cause pain (in low O conditions) ; 2 9 mutant F8 gene codes for non-functional factor VIII ; 10 haemophilia, recessive / sex-linked / on X chromosome ; 11 fibrinogen not changed to fibrin ; 12 blood clotting problem / risk of excessive bleeding ; 13 mutant HTT gene codes for abnormal huntingtin protein ; 14 Huntington’s disease dominant (disorder / allele) ; 15 ref. to additional / number of, CAG repeats ; 16 cognitive / movement, difficulty ; other human genetic conditions (max 2 conditions with 4 possible marks each) 17 mutant named gene codes for abnormal named protein ; ; 18 type of allele that causes named condition ; ; 19 biochemical detail re. gene / protein / molecule ; ; 20 physiological effect ; ; © Cambridge University Press & Assessment 2025 Page 18 of 18

2(a) gene 3 a section of DNA / sequence of (DNA) bases, coding for a (specific) polypeptide ; genotype all the alleles / alleles in an organism / (two) alleles of one gene ; phenotype (observable) features / characteristics / traits / appearance, (of an organism) ; © Cambridge University Press & Assessment 2025 Page 9 of 23 2(b) any four from: 5 1 mate / breed / cross, homozygous (parents) ; 2 dominant (parent) with recessive (parent) ; 3 to produce the F1, offspring / generation ; 4 (F1) offspring are heterozygotes ; 5 mate / breed / cross, F1 offspring / F1 generation / heterozygotes or self an F1 offspring (plant) ; 6 to produce the F2, offspring / generation ; plus 7 25% (F2) offspring are, homozygous dominant, / AA and 50% are, heterozygotes / Aa and 25% are, homozygous recessive / aa ; A a ratio e.g. AA Aa Aa aa 1 : 2 : 1 © Cambridge University Press & Assessment 2025 Page 10 of 23

3(a)(i) any three from: 3 1 glucose diffuses into the cell (through, A / transport protein) ; 2 idea that the enzyme / B, loses phosphate group ; 3 (dephosphorylated) B binds to lactose permease ; 4 causes, shape change / allosteric change, to lactose permease ; 5 lactose permease cannot function (so lactose cannot enter) ; 3(a)(ii) any two from: 2 1 no / less, (protein) synthesis of, lactose permease / β-galactosidase / transacetylase or no / less, transcription / expression, of (named structural) genes (of lac operon) ; 2 no / less, ATP / energy, wasted ; 3 no / fewer, amino acids wasted ; 4 glucose is respired more easily / AW or fewer steps / less energy, required to break down glucose or lactose has to be broken down (to glucose and galactose) ; © Cambridge University Press & Assessment 2025 Page 11 of 23 3(a)(iii) any three from: 3 1 splits into / forms, two, triose phosphate / TP (molecules) ; 2 (TP) oxidised / dehydrogenated, to pyruvate ; 3 ATP production ; 4 substrate-linked phosphorylation ; 5 production of reduced NAD ; © Cambridge University Press & Assessment 2025 Page 12 of 23 3(b)(i) any two from: 2 lactose diet 1 increases (over six days) ; no lactose diet 2 small increase / increases slightly / little change / stays around 50% (over six days) ; 3 comparative data quote – 2 percentages of either diet over time or percentage of each diet on one day ; time / days percentage lac+ ± 0.5 mm lactose diet no lactose diet 0 50 50 1 65.5 54 2 75.5 56.5 3 83.5 60 4 84 59 5 85 57.5 6 86 57 © Cambridge University Press & Assessment 2025 Page 13 of 23 3(b)(ii) any two from: 2 1 lactose is the selection pressure ; 2 (lac+), can metabolise / take up / AW, lactose (so survive) or lac-, cannot metabolise / take up / AW, lactose (so die) ; 3 AVP ; e.g. ref. glucose has run out Question Answer Marks

1(a)(i) AABB AABb AaBB AaBb ; ; 2 1(a)(ii) long chocolate ; 1 1(b) 4 A A a a A A a a ; B b B b B b B b AB Ab aB Ab AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb Ab AaBb Aabb aaBb aabb ; F2 offspring phenotype number ratio: 9 : 3 : 3 : 1 ; short short long long black chocolate black chocolate ; Mp 4 need phenotypes linked to genotypes by colour, symbol or initials 1(c) 1 structural gene codes for, (named) structural / functional, protein / polypeptide ; 2 2 regulatory gene codes for, transcription factor / repressor protein or regulatory gene, controls / helps / restricts, expression of (other) genes ; © Cambridge University Press & Assessment 2025 Page 8 of 18

2(a)(i) 2 E. turcicum Z. mays 1 chitin cell wall cellulose cell wall structural or or difference no chloroplasts chloroplasts or or hyphae / cells long and branching no hyphae / cells not long and branching or or syncytial / multinucleate / several nuclei per cell one nucleus per cell ; 2 heterotroph(ic) / parasitic / obtain food from host / do autotroph(ic) / phototrophic functional not photosynthesise / photosynthesis(e) ; difference 2(a)(ii) any four from: 4 1 large groups divide into smaller groups ; 2 common / similar / shared, features within a group ; 3 ref. three of: kingdom – phylum – class – order – family ; 4 genus and species = binomial / Linnaean / Latin / scientific, name ; 5 (both in domain) Eukarya ; 6 different kingdoms / Fungi and Plantae ; 2(b)(i) any two from: 2 1 low percentage leaf damage means high resistance (to infection) ; 2 SKV50 = 22% and CML153 = 58% ; 3 SKV50 shows greater resistance (to infection) ; 2(b)(ii) continuous ; 1 © Cambridge University Press & Assessment 2025 Page 9 of 18 2(b)(iii) any four from: 4 1 many / different / several / multiple, genes ; 2 affect, same trait / (percentage) area of leaf damage / resistance ; 3 alleles of, one / each, gene have a small effect ; 4 (different) genes have, additive / combined / interactive, effects ; 5 mathematical treatment to illustrate additive effect ; Question Answer Marks

10 marks from any two groups of mark points to max 6: 6 1 mutant TYR gene codes for non-functioning tyrosinase ; 2 albinism / albino, recessive (disorder / allele) ; 3 lack of melanin / no melanin produced ; 4 giving, pale / fair, skin / hair or giving, transparent / pink, iris ; 5 mutant HBB gene codes for, abnormal (β) globin / haemoglobin S ; 6 sickle cell, anaemia / disease, codominant (disorder / allele) ; 7 less soluble / sticky / rod-forming, haemoglobin makes red blood cells sickle ; 8 sickle cells, block capillaries / cause pain (in low O conditions) ; 2 9 mutant F8 gene codes for non-functional factor VIII ; 10 haemophilia, recessive / sex-linked / on X chromosome ; 11 fibrinogen not changed to fibrin ; 12 blood clotting problem / risk of excessive bleeding ; 13 mutant HTT gene codes for abnormal huntingtin protein ; 14 Huntington’s disease dominant (disorder / allele) ; 15 ref. to additional / number of, CAG repeats ; 16 cognitive / movement, difficulty ; other human genetic conditions (max 2 conditions with 4 possible marks each) 17 mutant named gene codes for abnormal named protein ; ; 18 type of allele that causes named condition ; ; 19 biochemical detail re. gene / protein / molecule ; ; 20 physiological effect ; ; © Cambridge University Press & Assessment 2025 Page 18 of 18

2(a) anaphase: K and M ; 4 cells containing pairs of homologous chromosomes: J and K ; crossing over: J ; haploid cells: L and M and N ; 2(b) any two from: 2 1 to prevent self-pollination / to ensure cross-pollination ; 2 so, must cross with / other parent must be / pollen comes from, a, different / selected, plant / parent / individual / variety ; 3 to make plant a female parent ; © Cambridge University Press & Assessment 2025 Page 8 of 17 2(c) any four from: 4 stage 1 – inbreeding to get two lines 1 inbreeding / line breeding ; 2 select for, disease resistance / rapid growth / high yield ; 3 select, best / desirable, offspring and cross with each other repeatedly ; 4 (results in) homozygous (loci) ; stage 2 – outcross to get uniform vigorous offspring 5 hybridise / outcross / outbreed, with another, variety / type of maize ; 6 with a different desired trait ; 7 AVP ; Question Answer Marks

5(a) any three from: 3 1 small so can keep, in small space / for low cost / with low maintenance ; 2 can select parents for, mating / cross-breeding / particular crosses ; 3 so get many, offspring / generations, in a short time ; 4 can be used to research, cancer / (named) neurodegenerative diseases ; 5 AVP ; © Cambridge University Press & Assessment 2025 Page 11 of 17 5(b) 6 1 symbols: A = grey bodya = black body B = long wing b = short wing ; F1 phenotypes: grey long x grey long 2 F1 genotypes: AaBb x (AaBb) ; AB Ab aB ab ; AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb ab AaBb Aabb aaBb aabb ; 5 F2 offspring phenotype number ratio: 9 : 3 : 3 : 1 ; 6 grey grey black black long short long short ; © Cambridge University Press & Assessment 2025 Page 12 of 17 5(c) 1 carry out a test cross / cross with a double homozygous recessive fruit fly / 3 cross with fly with black body and short wings ; plus any two from: 2 if some offspring have black body then F2 fly is, heterozygous for the body colour (gene) / Aa ; 3 if all offspring have grey body then F2 fly is, homozygous dominant for body colour (gene) / AA ; 4 if some offspring have short wings then F2 fly is, heterozygous for wing length (gene) / Bb ; 5 if all offspring have long wings then F2 fly is, homozygous dominant for wing length (gene) / BB ; Question Answer Marks

2(a)(i) range of values / range of phenotypes / intermediates ; 1 A do not fall into distinct groups 2(a)(ii) any three from: 3 1 environment has a large effect ; 2 example of environmental factor relevant to body mass ; e.g., diet, disease (loss of appetite, use of calories), exercise 3 interaction of environmental factors with genes or V = V + V ; P G E 4 (additive / combined, effect of), many genes / polygenes ; 2(b)(i) any two from: 2 1 (mutant POMC allele) causes increase in body mass ; 2 comparative data quote (in support of mp1) ; 3 heterozygous has intermediate, phenotype / mass or one mutant allele has an effect ; 4 overlap of, error / SD, bars between homozygous normal and heterozygous or non-overlap of, error / SD, bars between homozygous mutant and, heterozygous / homozygous normal ; 5 AVP ; e.g. variation in body mass within groups shows other factors also contribute / AW 2(b)(ii) eat more / do less exercise / AW ; 1 © Cambridge University Press & Assessment 2026 Page 10 of 25

5(a) Apply list rule for 4 responses 2 CPCP NN two or three correct = 1 mark CPCY NN four correct = 2 marks CPCP Nn CPCY Nn ; ; 5(b)(i) genotype: CBCY Nn ; 2 If both correct answers given but on wrong lines give 1 mark phenotype: brown without stripes ; ECF for a phenotype that matches a wrong genotype 5(b)(ii) any four from: 4 IGNORE crossing-over 1 independent / random, assortment / orientation (of 1 ALLOW each pair of, chromosomes / alleles, lines chromosomes / alleles / genes) ; up / separates / segregates, independently of other pairs 2 in metaphase I ; 2 ALLOW anaphase I if segregation described 2 DO NOT ALLOW metaphase / anaphase, II 3 ref. to genes, on separate chromosomes / not linked OR 3 CON ref. to breaking of linkage groups no linkage ; 4 gametes / (daughter) cells / products of meiosis, are, 4 ALLOW get one of each pair of, chromosomes / alleles for haploid / n ; ‘haploid / n’ 5 22 / 4, combinations, in dihybrid cross / with two genes OR 5 ALLOW digenic for ‘with two genes’ (get) CB N CB n CY N CY n ; © Cambridge University Press & Assessment 2026 Page 13 of 23 Trace ID: PC-791D658355 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/41 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 5(b)(iii) any three from: 3 1 CON sex linkage 1 (autosomal) linkage OR genes were, linked / on same 2 ALLOW words e.g. chromosome ; alleles for (brown + stripes) and (yellow + no stripes), inherited together / linked / on same chromosome 2 CB n, inherited together / linked / on same chromosome, 3 phenotypes were same as original parents and CY N, inherited together / linked / on same chromosome ; 3 (offspring showed) parental phenotypes ; 4 no, recombinants / crossing-over ; 5 as, genes / loci, tightly linked / close together ; © Cambridge University Press & Assessment 2026 Page 14 of 23 Trace ID: PC-791D658355 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/41 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 5(c) any four from: 4 ALLOW ORA throughout ECF after first CON to max 3 e.g. in rough grass brown snails selected for, survive and reproduce = CON mp2 then gets mp 1 and mp 3. 1 in woodland, non-yellow / brown / pink / unstriped, snails, are not seen / are camouflaged / are hidden / are not eaten / survive OR in rough grass, yellow / striped, snails, are not seen / are camouflaged / are hidden / are not eaten / survive ; 2 ORA non-yellow / brown / pink / unstriped, snails selected 2 in woodland, non-yellow / brown / pink / unstriped, snails against in rough grass have a selective advantage / are selected for OR OR yellow / striped, snails selected against in woodland in rough grass, yellow / striped, snails have a selective 2 ALLOW selection pressure favours for ‘selected for’ advantage / are selected for ; 2 ALLOW selection pressure is against for ‘selected against’ 3 ALLOW pass on genes (to offspring / next generation) for 3 in woodland, non-yellow / brown / pink / unstriped, snails, ‘reproduce’ reproduce / pass on alleles OR in rough grass, yellow / striped, snails, reproduce / pass on alleles ; 4 ORA in rough grass, non-yellow / brown / pink / unstriped, snails, decrease in frequency 4 in woodland, non-yellow / brown / pink / unstriped, snails, OR increase in frequency in woodland, yellow / striped, snails, decrease in frequency OR in rough grass, yellow / striped, snails, increase in frequency 5 ALLOW words e.g. allele for pink (shell) for ‘CP’ ; 5 in woodland, CB / CP / N, are selected for / increase (in frequency) OR in rough grass, CY / n, are selected for / increase (in frequency) ; © Cambridge University Press & Assessment 2026 Page 15 of 23 Trace ID: PC-791D658355 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/41 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

2(a) 2 A B A pointing to embryo ; B pointing to aleurone layer ; © Cambridge University Press & Assessment 2026 Page 8 of 23 Trace ID: PC-913B5F5E92 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/42 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(b)(i) C – (gibberellin / GA) receptor ; A GID1 3 D – DELLA (protein / repressor) ; E – transcription factor / phytochrome interacting factor / PIF ; 2(b)(ii) promoter ; 2 amylase ; A mRNA for amylase 2(c) decreases / short(er) / dwarf ; 1 Question Answer Marks

5(a) 4 parental phenotypes: ash-red male blue female parental genotypes: ZAZBr ZBlW ; offspring parental gametes ZBl W ZA genotype ZA ZBl genotype ZA W phenotype ash-red phenotype ash-red male female ZBr genotype ZBl ZBr genotype ZBr W phenotype blue phenotype brown male female allow one mark for correct parental gametes (in either orientation on the table) ; allow one mark for correct offspring genotypes ; allow one mark for correct matching colour and sex phenotypes ; if male parent is incorrect then ecf max 1 for correct offspring genotypes from gametes 5(b) sex-linkage ; 2 multiple alleles / dominance hierarchy ; © Cambridge University Press & Assessment 2026 Page 13 of 23 Trace ID: PC-913B5F5E92 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/42 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 5(c) 1 cross (ash-red male) with brown female ; Ignore genotype ZBr W 3 plus any two from: 2 if all offspring are ash-red then (male parent is), ZA ZA / AW ; A homozygous for ZA 3 if (any) offspring are blue then (male parent is), ZA ZBl / AW ; 4 if (any) offspring are brown then (male parent is), ZA ZBr / AW ; © Cambridge University Press & Assessment 2026 Page 14 of 23 Trace ID: PC-913B5F5E92 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/42 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

2(a) A – prophase II ; 3 B – telophase I ; A (early) prophase II C – metaphase II ; 2(b) any three from: 3 1 (chromosomes with) same, genes / gene loci ; 2 (but potentially) different alleles ; 3 one inherited from each parent / one maternal and one paternal chromosome ; 4 same, size / length ; 5 same, shape / position of centromere ; 6 AVP ; e.g. same banding pattern 2(c) any three from: 3 1 (meiosis) produces gametes ; 2 (gametes) are haploid / have one set of chromosomes ; 3 fertilisation / fusion of gametes, form a zygote ; 4 zygote, is diploid / has two sets of chromosomes ; 5 maintains chromosome number / prevents a change in chromosome number ; © Cambridge University Press & Assessment 2026 Page 9 of 20 Trace ID: PC-C51CA5D8F2 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/43 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

5(a) recessive 2 phenotype of (recessive) allele is masked by a dominant allele or two copies of the (recessive) allele are needed for phenotype (to be displayed) or alleles only affect the phenotype in the absence of a dominant allele or (genotype) must be homozygous for the (recessive) allele to affect the phenotype ; codominant both alleles affect the phenotype (in the heterozygote) ; 5(b) 3 blood group genotypes A IA IA IA IO ; B IB IB IB IO ; AB IA IB O IO IO ; © Cambridge University Press & Assessment 2026 Page 12 of 20 Trace ID: PC-C51CA5D8F2 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/43 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 5(c) parental phenotypes: ( B Rh+ O Rh+ ) 5 parental genotypes: IB IO Dd IO IO Dd parental IBD IBd IOD IOd gametes IOD IBIODD IBIODd IOIODD IOIODd B Rh+ B Rh+ O Rh+ O Rh+ IOd IBIODd IBIOdd IOIODd IOIOdd B Rh+ B Rh- O Rh+ O Rh- ratio of offspring phenotypes: B Rh+ O Rh+ B Rh- O Rh- 3 : 3 : 1 : 1 allow one mark for correct parental genotypes ; allow one mark for correct parental gametes ; allow one mark for correct offspring genotypes ; allow one mark for correct, matching, phenotypes ; allow one mark for correct ratio ; apply ecf – if incorrect parental phenotype for gene I, ecf for Rhesus gene, evidence of correct parental gametes, offspring genotypes and matching phenotypes to max 3 marks © Cambridge University Press & Assessment 2026 Page 13 of 20 Trace ID: PC-C51CA5D8F2 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/43 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

1(a) X attached to operator ; 1 1(b) 2 structural gene product role of gene product gene lacZ β-galactosidase hydrolyses lactose to form glucose and galactose lacY lactose permease idea that lactose can enter, or cell / bacterium β-galactoside permease lacA transacetylase transfers an acetyl group from one molecule to another One mark for each correct column 1(c) (enzyme that is only) produced when, the substrate / lactose / inducer, is present ; A in larger amounts 1 © Cambridge University Press & Assessment 2026 Page 8 of 22 Trace ID: PC-C13BFDE7F5 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/44 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(d) any four from: 4 B - population remains constant 1 ref. to glucose has been used up ; 2 (so bacterial) replication / division / binary fission, stops / slows ; B/C 3 lac operon / (named) structural gene(s), switched on / transcribed / expressed or (named) enzyme(s) synthesised ; C – population size increases 4 (so more) lactose enters ; 5 lactose, hydrolysed / broken down, into, glucose / galactose (to make ATP) ; 6 (for bacterial) replication / division / binary fission ; © Cambridge University Press & Assessment 2026 Page 9 of 22 Trace ID: PC-C13BFDE7F5 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/44 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

7(a) symbols ; e.g. N = NF1 allele 4 n = normal allele parents genotype Nn  nn gametes N n  n (n) ; offspring genotypes Nn (Nn) nn (nn) ; offspring phenotypes NF1 unaffected ; 7(b) any three from: 3 if test is negative 1 removes worry / AW ; if test is positive 2 early treatment ; 3 helps plan for the future or make informed decision whether to continue with pregnancy / family planning ; 4 ref. to counselling ; 5 discrimination / confidentiality / privacy ; 6 false positive / AW ; © Cambridge University Press & Assessment 2026 Page 17 of 22 Trace ID: PC-C13BFDE7F5 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/44 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 7(c) any three from: 3 idea of 1 no / less, resting membrane potential / stops Na+ K+ pumps from working ; 2 no / less, action potential / depolarisation or no / less, (voltage gated) sodium (ion) / potassium (ion), channels opening ; 3 no / less, impulse transmission / saltatory conduction / setting up of local circuits or damages, myelin sheaths / Schwann cells ; 4 no / less, synaptic transmission ; © Cambridge University Press & Assessment 2026 Page 18 of 22 Trace ID: PC-C13BFDE7F5 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/44 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/