Genetic technology

3(a) any four from: 4 1 gene(s) involved in production of carotene obtained ; 2 from, another species / bacteria / daffodil / maize / rice ; 3 ref. to use of named enzyme ; e.g. restriction enzyme / restriction endonuclease / (DNA) ligase 4 ref. to plasmid / vector / gene gun ; 5 ref. to recombinant DNA ; 6 ref. to insertion of gene into rice, cells / embryos / genome / DNA / chromosome ; 7 gene(s), expressed / transcribed, to produce enzyme(s) that make carotene ; 8 AVP ; e.g. extra detail such as promoter © UCLES 2021 Page 10 of 22 3(b) any four from: 4 1 33–34 grams of genetically modified rice needed (to meet the RDA of a child) ; 2 would help to prevent (childhood) blindness ; 3 would help to prevent death (of children) ; 4 (seeds) affordable / AW ; 5 (seeds) scientifically proven to be safe ; 6 (continuing to campaign would cause) waste of government money ; 7 AVP ; e.g. benefits outweigh concerns plant-based GM (no GM animal welfare concerns) would reduce the need for supplementing diets Question Answer Marks

10(a) any six from: 6 1 analysis of biological data using computer software / AW ; 2 databases of, gene / DNA / protein / amino acid, sequences ; 3 ref. to large databases ; 4 fast / accurate / efficient ; 5 ref. to allows data to be, shared / pooled ; 6 can predict, amino acid sequences / protein structure (from DNA sequence data) ; 7 ref. to analytical tool ; e.g. BLAST 8 ref. to comparisons ; 9 used to find methods to control parasites ; 10 named example of control ; e.g. vaccine 11 AVP ; e.g. personalised medicine identify new diseases ref. common ancestor phylogenetic analysis biodiversity / new species © UCLES 2021 Page 21 of 22 10(b) any nine from: 9 1 probes are, single-stranded DNA / ssDNA ; 2 each probe is unique to a particular gene ; 3 probes correspond to thousands of different genes ; 4 extract mRNA ; 5 mRNA used (as a template) to make cDNA ; R mRNA converted to cDNA 6 by reverse transcription / using reverse transcriptase ; 7 (c)DNA linked to fluorescent dye ; 8 (c)DNA added to microarray ; 9 (c)DNA, binds to / hybridises, to probes ; 10 by complementary base pairing ; 11 excess (c)DNA washed off ; 12 exposed to, UV light / laser ; 13 fluorescence shows the expressed genes / AW ; 14 intensity of fluorescence shows level of gene expression ; © UCLES 2021 Page 22 of 22

4(a) any five from: 5 1 (named) restriction, enzyme / endonuclease ; 2 cut / fragment, DNA ; 3 produced by / present in, bacteria / archaea / prokaryotes or to defend against, viruses / (bacterio)phages ; 4 (DNA) ligase ; 5 joins DNA / forms phosphodiester bonds / seals sugar-phosphate backbone ; 6 during DNA, repair / replication or joins Okazaki fragments ; 7 reverse transcriptase ; 8 forms / makes, (c)DNA from mRNA (template) ; 9 produced by / present in, retroviruses ; 10 DNA / Taq, polymerase ; 11 replicates / copies, DNA (at high temperatures) ; 12 produced by / present in, Thermus aquaticus ; 4(b)(i) any three from: 3 1 increased / higher / more, yield / production / harvest / food ; 2 increased / higher / better, quality of, produce / crops / food ; 3 decreased / lower / less, insecticide / pesticide, needed / used ; 4 decreased / lower / less, fuel use / CO emissions ; 2 5 potential for, set-aside / conservation areas (as less land needed for crops) ; 6 (described) comparative economic benefit ; 4(b)(ii) any two from: 2 1 people in other (named) continents eat GM, food / crops ; 2 GM, food / crops, already in (European) food chain ; 3 ref. to economic benefit of reducing GM (animal food) imports ; 4(b)(iii) 1 do not know / need to know, total crop area / non-GM crop area ; 2 2 so can work out, percentage / fraction, of, GM / non-GM ; © UCLES 2021 Page 9 of 16

4(a) diabetes: 2 insulin from (GM) bacteria ; A ref to, yeast / animal cells single gene disorder: gene therapy or insert, functional / normal / dominant, allele into, target / somatic / stem, cells or genome ; A gene R replacing one allele with another © UCLES 2021 Page 10 of 22 4(b)(i) any four from: 4 valid 1 GM spinach decreases number of, bacteria / E.coli or GM spinach has lowest number of, bacteria / E.coli ; 2 at all times (meat is stored) or the longer the time stored the more effective it is or most effective after 72 hours ; 3 data quote comparing no treatment or buffer alone with GM spinach extract at stated time ; time / hrs no treatment buffer alone buffer plus GM spinach 1 3.7–3.8 3.8–3.9 1.4–1.5 24 3.2–3.3 3.5–3.6 0.5–0.6 72 2.6–2.7 3.3–3.4 0.1–0.2 not valid 4 no treatment / buffer alone, (also) decrease number of, bacteria / E.coli or GM spinach does not kill all, bacteria / E.coli ; 5 meat should not normally be left at 10°C or people unlikely to eat meat left at, 10°C / for 72 hours ; 6 does not test effect on people / AW ; © UCLES 2021 Page 11 of 22 4(b)(ii) any three from: 3 1 may alter, taste / texture / quality, of meat ; 2 may be unsafe for humans / allergies / side effects ; 3 may harm, gut / beneficial, bacteria or may increase growth of, non-colicin sensitive / other, bacteria ; 4 contaminate food labelled as organic / AW ; 5 E.coli / bacteria, may develop resistance to, (spray / colicins) ; R GM spray / colicins, cause mutation 6 AVP ; e.g. may decrease food hygiene practices in, meat factories / abattoirs / restaurants / food outlets ; Question Answer Marks

4(a) any five from: 5 1 gene / DNA, from Bacillus thuringiensis ; 2 ref. to restriction, enzyme / endonuclease ; 3 clone gene / amplify gene, using PCR ; 4 insert, gene / DNA, into plasmid ; 5 add promoter ; 6 seal (plasmid) using DNA ligase ; 7 (maize) tissue / cell / callus / embryo, takes up plasmid / recombinant DNA ; 8 (maize) expresses new gene / produces Bt toxin ; 9 AVP ; e.g. Ti (plasmid) / Agrobacterium tumefaciens 4(b)(i) any two from: 2 1 pollen from Bt maize, kills / is toxic to / harms, caterpillars ; 2 pollen from non-Bt maize, does not kill / is not toxic to / does not harm, caterpillars ; 3 (eating) leaves with no pollen does not kill / is not toxic to / does not harm, caterpillars ; 4 more days of eating pollen from Bt maize gives more caterpillar deaths / AW ; © UCLES 2021 Page 10 of 22 4(b)(ii) any four from: 4 1 Bt pollen did not get deposited (onto milkweed plants) / AW ; 2 caterpillars and Bt maize located in different areas ; 3 pollen released at a different time to when caterpillars feed ; 4 ref. to caterpillars develop resistance (to Bt toxin) ; 5 ref. to lab and, quantity / toxicity, of Bt pollen ; 6 AVP ; e.g. in 2019 breeding conditions were better than in 1999 e.g. herbicides may reduce milkweed availability in maize fields © UCLES 2021 Page 11 of 22

9(a) any six from: 6 1 add marker gene to the, vector / plasmid ; 2 gene of interest inserted close to marker gene ; 3 (marker) gene product / protein, emits light ; 4 visible colour change ; 5 ref. to exposing to UV light / laser scanner ; 6 easy to identify transformed, bacteria / organisms ; 7 examples ; e.g. GFP 8 idea of no known risk ; 9 AVP ; e.g. ref. to gene of interest inserted into marker gene / insertional inactivation © UCLES 2021 Page 19 of 22 9(b) any five from: 9 advantages 1 increase in yield ; 2 improved quality / AW ; 3 improvement to health / Golden riceTM and vitamin A deficiency ; 4 longer shelf-life ; 5 some GM crops are adapted to unfavourable conditions ; A e.g. drought tolerance / nitrogen fixing / salt tolerance 6 (insect / herbicide, resistant crops) so less money spent on, pesticide / herbicide ; any five from: disadvantages 7 consumer resistance to GM crops ; 8 may be unsafe for humans / allergies / side effects / harm other animals ; 9 expensive ; 10 may have to buy seeds every season ; 11 seed and related herbicides sales monopolised by big companies ; 12 ref. to affects organic food ; © UCLES 2021 Page 20 of 22

4(a)(i) 1 crime scene DNA may be present in, small amount / minute quantity ; 2 2 PCR, amplifies / replicates / copies / multiplies, DNA ; 4(a)(ii) 1 (negative) DNA moves to, positive electrode / anode ; 2 2 smaller / lighter, fragments move, faster / further / longer distance ; © UCLES 2021 Page 10 of 21 4(b)(i) any two from: 2 1 (GEDmatch) database is large(r than police database) ; 2 police database only covers people, convicted of / suspected of, crime ; 3 GEDmatch has data for, innocent people / people with no reason to hide their DNA ; 4 provides multiple leads to guilty people who are hiding their DNA ; 4(b)(ii) any two from: 2 1 store of / large quantity of / contains, biological / DNA / genome, data / information ; 2 for, analysis / processing ; 3 by, computer / software / algorithm / statistics ; 4(b)(iii) any two from: 2 1 help police / catch criminals / imprison criminals ; 2 make, society / community, safe(r) ; 3 ref. to DNA breakthroughs help, justice / law and order ; 4 sharing own data also shares relations’ data without their consent ; 5 AVP ; © UCLES 2021 Page 11 of 21

4(a)(i) any four from: 4 1 obtain single-stranded DNA ; 2 label DNA with fluorescent, dye / tag / label ; 3 probes on, chip / microarray ; 4 each probe is unique to a particular, SNP / gene / allele ; 5 DNA (added), binds / hybridises, to probes ; 6 wash off excess DNA (after hybridisation) ; 7 (view under) UV light / laser scanner / high resolution digital camera ; 8 fluorescence indicates presence of, SNP / gene ; R gene expressed 4(a)(ii) any two from: 2 1 large database ; 2 use database to find, SNPs / probes ; 3 fast / accurate / efficient ; 4 ref. to (computer) software / algorithms ; 5 ref. to statistics / statistical analysis ; 6 idea of, 17 000 × 500 000 / 8.5 × 109, data points ; 4(b)(i) 1 and 6 ; 1 © UCLES 2021 Page 12 of 24 4(b)(ii) any two from: 2 1 all diseases, are autosomal / not associated with X chromosome / not sex-linked ; 2 all diseases are associated with SNP on chromosome 6 ; 3 type 1 and type 2 diabetes SNPs are associated with chromosomes 12 and 16 (but not rheumatoid arthritis) ; 4 type 2 diabetes SNP associated with chromosome 10 (but not type 1 diabetes and rheumatoid arthritis) ; 5 arthritis and type 1 diabetes have higher level of association (with each other) than with type 2 diabetes ; 6 rheumatoid arthritis has fewest number of SNPs or type 1 and type 2 diabetes has more SNPs (than rheumatoid arthritis) ; © UCLES 2021 Page 13 of 24 4(c) any three from: 3 1 DNA analysis not available for everyone ; 2 lifestyle change ; A e.g. lose weight / stop smoking / take exercise 3 early treatment ; 4 allows people to plan ; e.g. organise care / appoint power of attorney / take out medical insurance / make will / gift property to children / retire early 5 decide whether to have children / ref. (therapeutic) termination ; 6 results may cause, anxiety / stress / panic / depression (if positive) or reduce worry (if negative) ; 7 results may affect ability to get, insurance / credit / jobs ; 8 idea of predictions may not be accurate ; Question Answer Marks

4(a)(i) 1 crime scene DNA may be present in, small amount / minute quantity ; 2 2 PCR, amplifies / replicates / copies / multiplies, DNA ; 4(a)(ii) 1 (negative) DNA moves to, positive electrode / anode ; 2 2 smaller / lighter, fragments move, faster / further / longer distance ; © UCLES 2021 Page 10 of 21 4(b)(i) any two from: 2 1 (GEDmatch) database is large(r than police database) ; 2 police database only covers people, convicted of / suspected of, crime ; 3 GEDmatch has data for, innocent people / people with no reason to hide their DNA ; 4 provides multiple leads to guilty people who are hiding their DNA ; 4(b)(ii) any two from: 2 1 store of / large quantity of / contains, biological / DNA / genome, data / information ; 2 for, analysis / processing ; 3 by, computer / software / algorithm / statistics ; 4(b)(iii) any two from: 2 1 help police / catch criminals / imprison criminals ; 2 make, society / community, safe(r) ; 3 ref. to DNA breakthroughs help, justice / law and order ; 4 sharing own data also shares relations’ data without their consent ; 5 AVP ; © UCLES 2021 Page 11 of 21

5(a)(i) haemophilia (A) ; 1 5(a)(ii) any two from: 2 accept ora throughout 1 large / unlimited, supply ; 2 no risk of infection ; 3 no / fewer, ethical issues ; 4 less chance of, rejection / immune response / allergic response / side effects ; 5 cheap / quick, to produce ; 6 no need to wait for donor ; 5(b)(i) reverse transcriptase ; 1 5(b)(ii) 1 genes cut from (donor) DNA ; 2 2 genes synthesised (chemically) from nucleotides ; 5(c) any two from: 2 1 required, for gene expression / to start transcription ; 2 (so) transcription factor can bind (to promoter) ; 3 so RNA polymerase can bind (to promoter) ; © UCLES 2022 Page 15 of 22

4(a) 5 statement genetic engineering gene editing using a plasmid It can produce a transgenic organism.   ; It can modify the characteristics of an organism.   ; It can delete unwanted DNA.  ; It uses an enzyme that cuts DNA.   ; It can use RNA to precisely locate the target gene.  ; 4(b)(i) A ; 1 4(b)(ii) any three from: 3 1 more food / increase yield / help solve global demand for food ; 2 improves quality of, fruit / oranges / crop ; 3 more income for, growers / farmers ; 4 cheaper / lower cost, fruit / oranges / food (to consumer) ; 5 spend less on / use less / no need for, (bactericidal) chemicals / pesticides ; © UCLES 2022 Page 11 of 19

4(a) 5 statement genetic engineering gene editing using a plasmid It may cause the   ; organism to produce a different protein. It may cause a single  ; base pair in a gene to be changed. The success of the  ; technique can be evaluated using marker genes. It may use the CRISPR  ; system. It uses DNA ligase.  ; 4(b)(i) C ; 1 © UCLES 2022 Page 10 of 22 4(b)(ii) any three from: 3 1 increased / high, (crop) yield ; 2 idea of less food shortages / more food production / helps solve global demand for food ; 3 less need to remove weeds (by hand) ; 4 more income for, growers / farmers or ref. to economic benefit for, country / region ; 5 cheaper / lower cost, to buy ; 6 AVP ; e.g. less need for deforestation of other land © UCLES 2022 Page 11 of 22

4(a) 5 statement genetic engineering gene editing using a plasmid It can add a new phenotypic characteristic to an organism.   ; It can change an A-T base pair to C-G.  ; It can inactivate a desired selected gene in an organism.  ; It may change DNA in a way that cannot be told apart from a  ; natural mutation. It requires a DNA donor and a recipient.  ; 4(b)(i) A ; 1 4(b)(ii) any three from: 3 1 less food waste ; A increases quality of food 2 idea of less food shortages / more food production / helps solve global demand for food ; 3 more income for, growers / farmers or ref. economic benefit for, country / region ; 4 crop can be grown, when there is a water shortage / in poor quality soil / in harsh environment ; © UCLES 2022 Page 12 of 23

4(a) any four from: 4 1 add DNA to give a new (named), characteristic / protein ; 2 restriction, enzyme / endonuclease, to obtain, gene / allele / section of DNA or restriction, enzyme / endonuclease, to cut plasmid ; 3 combine gene with / insert gene into, vector / plasmid ; 4 introduce, (recombinant) vector / plasmid, to, bacterium / (named host) cell ; 5 clone / multiply, (named, recombinant / GM) organism ; 6 AVP ; 4(b)(i) 1 stem cells, proliferate / divide / multiply / make new cells ; 2 2 (correct) gene is, inherited by / passed on to / present in, new cells ; 4(b)(ii) any two from: 2 1 to switch gene on / so gene is expressed / allow transcription ; 2 at right time / all the time / in sufficient quantities ; 3 to allow binding of, RNA polymerase / transcription factors ; © UCLES 2022 Page 10 of 19 4(b)(iii) any two from: 2 1 retrovirus / new gene, could / must not, insert in wrong place / disrupt other genes ; 2 could / must not, cause cancer ; 3 could / must not, cause, infection / disease ; 4 could / must not, cause, immune / allergic, response ; 5 AVP ; 4(c) any three from: 3 1 HD is caused by a dominant allele ; 2 adding a ‘normal’ recessive allele would not work ; 3 gene editing can / we need to, delete / remove / inactivate, HD / mutant, allele / DNA ; 4 ref. (surplus CAG) repeats / triplets / stutter ; © UCLES 2022 Page 11 of 19

4(a) any four from: 4 1 manipulate DNA to modify organism’s characteristics / AW ; 2 gene / allele / (section of) DNA, obtained using restriction, enzyme / endonuclease ; 3 use of reverse transcriptase to make, gene / allele / (section of) DNA, using mRNA ; 4 gene / allele / (section of) DNA, inserted into, vector / plasmid, using ligase ; 5 add / insert, (recombinant), vector / plasmid, into, (host) cell / bacterium ; 6 clone / multiply, cell / bacteria ; A put bacteria in a fermenter 7 gene is expressed and, protein / factor XIII / factor IX, is made ; 8 AVP ; e.g. artificial / chemical, synthesis of new gene 4(b)(i) any three from: 3 1 haemophilia B (first) because (F9) gene is small enough to fit into virus / 1.6kbp and 4.7kbp ; ora 2 haemophilia A (first) because it is more common ; ora therapy not attempted 3 (because) disease can be managed by recombinant proteins ; 4 gene therapy (trials) involve, risk of harm / side effects / allergic reactions / immune response ; therapy attempted 5 provides a cure / AW ; 6 taking clotting factors etc. can involve risk of harm ; © UCLES 2022 Page 10 of 19 4(b)(ii) any two from: 2 1 to allow binding of, RNA polymerase / transcription factors ; 2 to switch gene on / so gene is expressed / allow transcription (of gene) ; 3 at right time / all the time / in sufficient quantities ; 4 in correct tissue ; 4(b)(iii) any two from: 2 decrease success because: 1 antibodies / immune response, may, destroy / attack / AW, virus / vector ; 2 (so) limiting / stopping, delivery of, gene / allele / DNA, to cells ; 3 destroys GM cells or destroys cells that have successfully taken up the, virus / gene / allele / DNA ; 4(c) any two from: 2 list rule 1 (gene editing) is, precise / exact / accurate ; 2 patient’s own gene can be, edited / corrected or no introduction of, gene / allele ; 3 no need to introduce promoter ; 4 less / no, risk of cancer or less / no, immune response ; © UCLES 2022 Page 11 of 19

4(a) any four from: 4 1 add DNA to give a new (named), characteristic / protein ; 2 restriction, enzyme / endonuclease, to obtain, gene / allele / section of DNA or restriction, enzyme / endonuclease, to cut plasmid ; 3 combine gene with / insert gene into, vector / plasmid ; 4 introduce, (recombinant) vector / plasmid, to, bacterium / (named host) cell ; 5 clone / multiply, (named, recombinant / GM) organism ; 6 AVP ; 4(b)(i) 1 stem cells, proliferate / divide / multiply / make new cells ; 2 2 (correct) gene is, inherited by / passed on to / present in, new cells ; 4(b)(ii) any two from: 2 1 to switch gene on / so gene is expressed / allow transcription ; 2 at right time / all the time / in sufficient quantities ; 3 to allow binding of, RNA polymerase / transcription factors ; © UCLES 2022 Page 10 of 19 4(b)(iii) any two from: 2 1 retrovirus / new gene, could / must not, insert in wrong place / disrupt other genes ; 2 could / must not, cause cancer ; 3 could / must not, cause, infection / disease ; 4 could / must not, cause, immune / allergic, response ; 5 AVP ; 4(c) any three from: 3 1 HD is caused by a dominant allele ; 2 adding a ‘normal’ recessive allele would not work ; 3 gene editing can / we need to, delete / remove / inactivate, HD / mutant, allele / DNA ; 4 ref. (surplus CAG) repeats / triplets / stutter ; © UCLES 2022 Page 11 of 19

2(a)(i) 1 is regulatory gene / codes for repressor (protein) ; R is a transcription factor 2 R lacI is a repressor protein 2 prevents, transcription / RNA polymerase binding to promoter ; 2(a)(ii) any three from: 3 concentration of IFN- produced 1 increases steeply (after addition of IPTG) ; 2 peak is, at 8 hours / 4 hours (after addition of IPTG) ; 3 decrease is less steep or final concentration greater than starting concentration / AW ; 4 data quote ; 2(a)(iii) any one from: 1 IPTG is higher / lactose is lower, because 1 lactose has to be converted to allolactose ; 2 lactose is broken down so needs to be continually taken up or IPTG is not broken down so continually binds to repressor ; 3 IPTG will be at higher concentration than allolactose ; A lactose for allolactose 4 IPTG has higher affinity for repressor protein than allolactose ; A lactose for allolactose 5 lactose, used up / concentration decreases ; 6 more IPTG enters ; © UCLES 2023 Page 6 of 20 2(a)(iv) IFN- is, unstable / breaks down ; 1 2(b) (only E. coli that have taken up the plasmid) will, grow / survive, in the presence of, ampicillin / antibiotic ; 1 2(c) any five from: 5 1 (random) mutation ; 2 natural selection / directional selection ; 3 antibiotic acts as selection pressure / AW ; 4 bacteria with mutation, have selective advantage / survive / reproduce or bacteria with, gene / allele, that codes for antibiotic resistance, have selective advantage / survive / reproduce ; 5 pass on, mutation / gene / allele, (for antibiotic resistance) by, binary fission / asexual reproduction / vertical transmission ; 6 pass on, mutation / gene / allele, (for antibiotic resistance) by, transduction / transformation / conjugation / horizontal transmission ; 7 AVP ; e.g. increased chance of resistance if people do not finish full course of antibiotics overuse of antibiotics some antibiotics may act as mutagens © UCLES 2023 Page 7 of 20

3(a) any three from: 3 max two from: 1 (phenotype has) range of values / intermediates ; 2 (phenotypes) not, in groups / in classes / categoric / discrete / qualitative or (phenotypes are) quantitative ; 3 normal distribution ; max two from: 4 polygenic / controlled by many genes ; 5 different genes / alleles, have additive effect ; 6 (named) environmental factors (contribute to the variation) ; 3(b)(i) difference between means = 9.4 – 7.7 or 1.7 ; 3 2 2 0.4 + 1.1 denominator = 28 27 or 0.16 + 1.21 28 27 or 0.22 / 0.23 (no limit on number of decimal places) ; t = 7.56 ; must be to 2 decimal places allow ECF © UCLES 2023 Page 8 of 20 3(b)(ii) 1 t-value / 7.56, is greater than, 2.01 / critical value ; 3 2 difference between two groups is, significant / not due to chance or null hypothesis rejected ; any two from: 3 overlap in, data range / error bars ; 4 ref. to correlation does not prove causation ; 5 only a single investigation / needs repeating / small sample size ; 6 ref. to this is only at 5% probability so may not actually be different / AW ; 7 t-test may not be valid due to unequal, standard deviations / variances; 3(b)(iii) any one from: 1 1 idea of less labour intensive ; e.g. no need for weekly injections / GM only needs to be done once 2 idea of less stressful on GM salmon ; 3 risk of infection with injections ; 4 idea that growth hormone is continuously produced ; 5 GM salmon may grow faster ; © UCLES 2023 Page 9 of 20

4(a) any three from: 3 1 ref. to isolate / extract, DNA, from, cells / tissue / named ; 2 ref. to cut DNA, into small fragments / using restriction enzymes ; 3 ref. to denature / AW, into single-stranded DNA ; 4 add fluorescent, tag / marker / dye ; 4(b)(i) 2 400 000 or 2 500 000 ; 1 4(b)(ii) any three from: 3 1 DNA from DiGeorge syndrome and control DNA labelled with different colour fluorescent tags ; 2 DNA hybridises with probes (on microarray) ; DiGeorge Syndrome 3 less DNA binds to probes (than control DNA) ; 4 so there is, less / 50%, fluorescence where nucleotides have been deleted ; 5 fluorescence is, equal / 100%, where nucleotides have not been deleted ; © UCLES 2023 Page 10 of 20 4(b)(iii) any three from: 3 1 different number of nucleotides may be deleted ; 2 different genes may be deleted ; 3 an individual only has one allele (of the deleted genes) ; 4 different individuals may have different alleles of the same gene or in one individual remaining allele may be recessive but dominant in another individual ; 5 so different proteins made ; 6 ref. to individuals may have different environments ; A diet © UCLES 2023 Page 11 of 20

4(a)(i) DNA, combined / joined, from, two / different, organisms / sources ; 1 4(a)(ii) any three from: 3 (protein made in, bacteria / yeast, so) 1 can be made in, large / unlimited, quantities ; 2 cheap to make / low cost / cost-efficient ; 3 does not, harm / involve, animals / pigs / cows ; 4 no risk of (named) disease, transfer / infection ; (sequence identical to human sequence so) 5 does not cause, allergy / inflammatory response / immune response / antibody production ; 6 acts more rapidly ; 7 do not, develop tolerance to it / need larger doses ; 4(b)(i) cow ; 1 4(b)(ii) any three from: 3 1 obtain (normal human), gene / DNA, from (m)RNA by reverse transcriptase / using restriction enzyme ; 2 use gene editing (to alter human gene) ; 3 obtain (nucleotide) sequence for (normal human) insulin gene ; 4 synthesise, new / analogue, gene / nucleotide sequence ; 5 put, new / analogue, gene in, bacteria / yeast ; 6 add promoter for, gene expression / protein synthesis ; 7 AVP ; 4(c) any three from: 3 1 can, share / search / access, data(base) / information / sequences ; 2 from anywhere / online ; 3 can, compare / align / analyse, (multiple) sequences ; 4 rapid / fast(er) (process) ; 5 can, quantify / count, nucleotide differences ; 6 closely-related species have few, differences / mutations ; © UCLES 2023 Page 11 of 17

4(a) Bacteria and Archaea ; 1 4(b) any four from: 4 1 obtain (specific restriction endonuclease) gene, qualified ; e.g. gene extracted from the, DNA / genome, of E. coli / bacteria gene synthesised from the mRNA of E. coli / bacteria gene synthesised from nucleotides 2 PCR to make more copies of, gene / DNA ; 3 cut a plasmid, with a restriction enzyme / to give sticky ends ; 4 combine / mix / join, gene with plasmid using ligase ; 5 add plasmid to, E. coli / bacteria ; A transformation of E. coli 6 use marker genes to, select / identify, bacteria / E. coli, with recombinant plasmids ; 7 ref. culture bacteria / use fermenter ; 8 ref. extraction / purification (of enzyme) ; 9 AVP ; e.g. heat shock / calcium ions / electroporation (detail mp5) complementary sticky ends anneal / make phosphodiester bonds (detail mp4) © UCLES 2023 Page 12 of 25 4(c) any three from: 3 1 (data stored is) a large amount of, amino acid / nucleotide / base / DNA, sequences ; 2 share data / access data quickly ; 3 compare (amino acid / nucleotide / base / DNA) sequences ; 4 use to, predict / visualise / model, the structure of the enzyme ; 5 identify restriction endonuclease to use or find / discover, new restriction endonucleases ; © UCLES 2023 Page 13 of 25 4(d) any four from: 4 feature electrophoresis chromatography 1 separation role both – are separating techniques or both – involve movement of substances ; 2 molecule separated DNA / RNA / proteins pigments / named pigment / amino acids ; 3 medium gel / named gel paper / glass / silica gel / named medium ; 4 separated by (electric) solvent / named solvent current / electric field / electricity ; 5 separated due to charges / polarity / solubilities / mass lengths / mass both – separate by mass ; 6 visualisation using dyes / different colours of ethidium bromide / pigments / dyes not added / UV light UV light not used both - dyes can be added (if TLC) ; 7 identification by use, DNA use R value f ladder / known length of DNA or use of DNA probe ; both - use of, references / known values © UCLES 2023 Page 14 of 25

3(a)(i) the operon has: 3 promoter ; operator ; three structural genes / named three structural genes ; lacZ or  galactosidase gene lacA or lactose /  galactoside, permease gene lacY or transacetylase gene I regulatory genes / order of named parts 3(a)(ii) any four from: 4 lacI gene 1 is always expressed ; 2 controls (structural) gene expression ; 3 codes for the repressor (protein) ; 4 repressor, binds to the operator / blocks the promoter ; 5 prevents, (structural) gene expression / RNA polymerase binding to promoter ; 6 lactose / allolactose, binds to repressor ; 7 (so) repressor cannot bind to operator / promoter unblocked / gene expression can occur ; © UCLES 2023 Page 9 of 24 3(b) 1 enzymes / proteins, made continuously / all the time ; 3 2 (because) enzymes / proteins, needed / necessary (for cell) ; 3 end product inhibition / made until product concentrations too high ; Question Answer Marks

4(a) any three from: 3 1 donor not needed ; 2 immediate effect ; 3 idea that easy to administer treatment ; 4 no immune response / no rejection ; 5 less invasive ; 6 AVP ; e.g. lower risk to health / cheaper / quicker © UCLES 2023 Page 10 of 24 4(b) any four from: 4 1 given a drug to increase number of stem cells (in bone marrow) ; 2 ref. to virus / vector, containing, normal / healthy, allele ; 3 remove, bone marrow / stem cells ; 4 mix stem cells with, viral / vector (to allow transfer of normal allele) ; 5 radiotherapy / drug, to make space in bone marrow / to kill stem cells (in bone marrow) ; 6 (transduced stem) cells, infused / injected, into blood ; 7 (lymphocytes) produce functioning ADA ; 8 AVP ; e.g. (gamma) retrovirus / adeno-associated virus e.g. tissue from bone marrow, purified / sorted, to obtain stem cells e.g. cells are grown in culture to check the ADA gene is active © UCLES 2023 Page 11 of 24 4(c) any three from: 3 1 expensive ; 2 cure / long term treatment / no longer chronically ill / better quality of life ; 3 no need for regular, injections / treatments or only a single treatment ; 4 cultural / religious, objections ; 5 no donor needed ; 6 ref. more money available to health system in the long term ; 7 may cause cancer ; 8 stressful ; © UCLES 2023 Page 12 of 24

4(a)(i) 1 DNA, joined / combined / made, from two / different, sources / species ; 2 2 using (named), enzymes / vectors or to create a, GMO / transgenic organism ; 4(a)(ii) to, test / compare, effect(iveness) of, genes / proteins / Bt and OCII / plants / varieties / A and B 1 or to see which, (gene / plant / variety / of A and B), works, better / best ; 4(a)(iii) to compare / provide a baseline / as a control ; 1 © UCLES 2023 Page 10 of 16 4(b) 1 A and B kill larvae ; 3 2 GM increases, yield of / food from (potatoes) ; 3 A, is best / kills most / works faster / should be grown / will provide most food ; Question Answer Marks

8(a) letter X on rising slope to the left of the angle where line plateaus ; 1 8(b)(i) reverse transcriptase ; 1 8(b)(ii) transcription factor(s) ; 1 © UCLES 2023 Page 13 of 16 8(b)(iii) any three from: 3 1 in high light intensity plant can photosynthesise more ; 2 so they need (more) / upregulate / increase / make (more) (named) enzymes / proteins, for photosynthesis ; 3 (plus) named, enzyme / protein (for photosynthesis) ; 4 (named) pigments to protect cells from excess light ; 5 enzymes to make, sucrose / starch / amino acids ; 6 proteins for, sucrose / amino acid, transport ; 7/8 AVP ;; e.g. DELLA breaks down releasing, phytochrome interacting factors / PIF Question Answer Marks

10 any seven from: 7 1 genetic engineering / recombinant (DNA technology) ; 2 (named) drug / treatment / protein, from, (GM) bacteria / (GM) yeast / (named) (GM)O ; 3 make insulin (drug for diabetes) ; 4 make factor VIII (drug for haemophilia) ; 5 make adenosine deaminase (drug for SCID) ; 6 genetic, screening / diagnosis / testing ; 7 (detect) BRCA1 / BRCA2 ; 8 (detect number of repeats / allele for) Huntington’s ; 9 (detect allele for) cystic fibrosis / CFTR ; 10 example of action if diagnosis positive ; 11 gene therapy ; 12 insert / add, normal allele into (named), cells / tissue (of person) ; 13 to treat, eye disease(s) / LCA / Leber’s congenital amaurosis ; 14 to treat SCID ; 15/16 AVP ; ; e.g. ref. to help / develop, xenotransplantation GM / antigen-free, pigs / animals, to source, tissues / organs, for transplants GM plants to make vaccines GM / recombinant / DNA / mRNA, vaccines recombinant antibody technology other / different, recombinant therapeutic protein / genetic screening / gene therapy, example © UCLES 2023 Page 16 of 16

4(a) any four from: 4 1 marker gene added with gene of interest (GOI) ; 2 use same promoter ; 3 (so) both genes, transcribed / expressed (together) ; 4 (so) both proteins are produced ; 5 use UV light (to detect fluorescence) ; 6 fluorescence shows, transcription / expression, of gene of interest (GOI) ; 7 AVP ; e.g. fluorescent proteins not harmful / have no effect on plant / do not affect quantity of desired protein produced © UCLES 2023 Page 9 of 18 4(b) any two from: 2 1 high / increase in, yield / productivity / quality or more food ; 2 increased income / reduce costs ; 3 can use herbicides / AW ; 4 less / no, competition ; 5 no need to plough / less labour intensive ; 4(c)(i) complementary (base pairing between DNA strands) / described ; 1 4(c)(ii) any two from: 3 1 use mRNA to make (ss)cDNA ; 2 fluorescent, tag / dye / substance / label, attached to cDNA ; 3 hybridisation / binding, of cDNA to probe ; 4 use, lasers / UV light, to produce fluorescence ; plus 5 idea of intensity of, fluorescence / light, indicates level of (gene) expression ; © UCLES 2023 Page 10 of 18

4(a)(i) 1 DNA, joined / combined / made, from two / different, sources / species ; 2 2 using (named), enzymes / vectors or to create a, GMO / transgenic organism ; 4(a)(ii) to, test / compare, effect(iveness) of, genes / proteins / Bt and OCII / plants / varieties / A and B 1 or to see which, (gene / plant / variety / of A and B), works, better / best ; 4(a)(iii) to compare / provide a baseline / as a control ; 1 © UCLES 2023 Page 10 of 16 4(b) 1 A and B kill larvae ; 3 2 GM increases, yield of / food from (potatoes) ; 3 A, is best / kills most / works faster / should be grown / will provide most food ; Question Answer Marks

8(a) letter X on rising slope to the left of the angle where line plateaus ; 1 8(b)(i) reverse transcriptase ; 1 8(b)(ii) transcription factor(s) ; 1 © UCLES 2023 Page 13 of 16 8(b)(iii) any three from: 3 1 in high light intensity plant can photosynthesise more ; 2 so they need (more) / upregulate / increase / make (more) (named) enzymes / proteins, for photosynthesis ; 3 (plus) named, enzyme / protein (for photosynthesis) ; 4 (named) pigments to protect cells from excess light ; 5 enzymes to make, sucrose / starch / amino acids ; 6 proteins for, sucrose / amino acid, transport ; 7/8 AVP ;; e.g. DELLA breaks down releasing, phytochrome interacting factors / PIF Question Answer Marks

10 any seven from: 7 1 genetic engineering / recombinant (DNA technology) ; 2 (named) drug / treatment / protein, from, (GM) bacteria / (GM) yeast / (named) (GM)O ; 3 make insulin (drug for diabetes) ; 4 make factor VIII (drug for haemophilia) ; 5 make adenosine deaminase (drug for SCID) ; 6 genetic, screening / diagnosis / testing ; 7 (detect) BRCA1 / BRCA2 ; 8 (detect number of repeats / allele for) Huntington’s ; 9 (detect allele for) cystic fibrosis / CFTR ; 10 example of action if diagnosis positive ; 11 gene therapy ; 12 insert / add, normal allele into (named), cells / tissue (of person) ; 13 to treat, eye disease(s) / LCA / Leber’s congenital amaurosis ; 14 to treat SCID ; 15/16 AVP ; ; e.g. ref. to help / develop, xenotransplantation GM / antigen-free, pigs / animals, to source, tissues / organs, for transplants GM plants to make vaccines GM / recombinant / DNA / mRNA, vaccines recombinant antibody technology other / different, recombinant therapeutic protein / genetic screening / gene therapy, example © UCLES 2023 Page 16 of 16

4(a) 1 temperature increases and milk yield decreases ; 2 2 comparative data quote – April = 10 °C and 792–798 kg cow–1, August = 18 °C and 711–716 kg cow–1 ; 4(b) 1 continuous 3 and (milk yield) does not fall into distinct classes / shows a range / intermediates / no distinct categories / AW ; 2 environment and (milk yield) affected by air temperature ; 3 genetic / polygenic and many / 20, genes have effect (on milk yield) or heat-tolerant cattle have lower milk yield than Holstein Friesian cattle ; © Cambridge University Press & Assessment 2024 Page 9 of 21 4(c) any three from: 3 1 SLICK allele increases milk yield (in both months / at both temperatures) ; 2 in March / at 5 °C, there is a small difference (between milk yield) ; 3 in September / at 14 °C, there is a larger difference (between milk yields) ; 4 cattle with SLICK allele maintain milk yield (in both months / at both temperatures) ; 5 comparative data quote to support mp1–mp4 ; Month Holstein without Holstein with SLICK / kg cow–1 SLICK / kg cow–1 March / at 5 °C 780–785 795–800 Sept / at 14 °C 690–700 770–780 © Cambridge University Press & Assessment 2024 Page 10 of 21 4(d) any six from: 6 gene editing selective breeding 1 (first) offspring have SLICK allele ; 2 can have, negative / unknown, effects ; 3 presence of SLICK allele (in offspring) can be confirmed by, ; genetic testing / phenotypic observation 4 done by humans / artificial methods ; 5 only, and affects many genes ; PRLR / one, gene is affected 6 all offspring have SLICK allele and some offspring have SLICK allele ; 7 immediate / one generation and performed over (many) generations ; 8 performed on, and mating ; embryos / zygotes / cells / artificial insemination 9 technical requirements and mating / performed on the farm ; e.g. laboratory, training, molecular e.g. physiological method method 10 maintains, heterozygosity / genetic and loss of, heterozygosity / genetic ; variation / variation / desirable characteristics desirable characteristics 11 regulatory approval and no regulatory approval ; 12 no outbreeding required and outbreeding required ; © Cambridge University Press & Assessment 2024 Page 11 of 21

4(a) any four from: 4 1 (random / spontaneous) mutation gave resistance ; 2 pathogen / disease / plague, was selection pressure ; 3 mutation, gave selective advantage / was selected for / allowed crayfish to survive (plague) ; 4 survivors / resistant crayfish, bred / reproduced / passed on mutation ; 5 frequency of, allele / mutation, (for resistance) increased ; 6 natural / directional, selection ; 7 AVP ; 4(b)(i) 1 (heat to) 90–98 °C so DNA, denatures / strands separate ; 4 2 (cool to) 50–65 °C so primers, bind / base pair / anneal (to DNA) ; 3 (heat to) 68–75 °C so, Taq / DNA, polymerase, makes DNA / (new) strand ; 4 repeat cycles to amplify DNA ; 4(b)(ii) used, a (named) database / bioinformatics ; 1 © Cambridge University Press & Assessment 2024 Page 8 of 15 4(c)(i) A ; 1 4(c)(ii) (23) = 8 ; 1 4(d)(i) (named) plasmid / vector (used) ; 3 (containing) gene / DNA, for (green) fluorescent protein ; (containing) a (prokaryotic) promoter ; 4(d)(ii) to act as a, marker / reporter, gene 1 or to identify, recombinant / GM / transgenic, bacteria / organisms or to show expression of another transferred gene ; Question Answer Marks

5(a) 1 family history of, breast / ovarian, cancer ; 4 plus any three from: 2 (mutation causes) change of primary structure (of tumour suppressor protein) ; 3 changes, folding / bonding / 3D shape / tertiary structure (of tumour suppressor protein) ; 4 non-functional (tumour suppressor) protein formed ; 5 DNA is not repaired / cells with damaged DNA do not die ; 6 (so) increases number of mutations / mutations accumulate ; 7 (some mutations) cause uncontrollable, cell division / mitosis (of breast cells) ; 5(b) 1 only small amount of DNA available ; A gene 2 2 amplify, DNA / (BRCA1) gene ; 5(c) 6.1  104 ;; A 6.125  104 for two marks 2 allow one mark for 61 250 or 3.5107 = 8.75  104 or 87 500 400 © Cambridge University Press & Assessment 2024 Page 11 of 20 5(d) any two from: 2 supports: 1 (women with BCRA1) have a higher probability of survival ; ora 2 (for women with BRCA1) the probability of survival decreases less or there is a smaller rate of decrease of probability of survival or bigger difference between the two groups over time for the probability of survival ; ora 3 data quote to show differences between the survival of the two groups at a particular time ; probability of survival time / months with mutation without mutation 0.975 30 0.85 range 0.975 – 0.988 60 0.95 0.75 0.675 90 0.85 range 0.675 – 0.688 0.63 120 0.75 range 0.613 – 0.625 150 0.75 0.55 0.7 / 0.70 0.475 / 0.474 / 0.47 180 range 0.7 – 0.71 range 0.46 – 0.475 4 study carried out for, a long time / 15 years ; does not support: 5 no statistical test carried out / ref. to sample size ; © Cambridge University Press & Assessment 2024 Page 12 of 20

4(a)(i) restriction endonuclease 4 1 cuts, DNA / plasmid ; DNA ligase 2 joins DNA with the plasmid ; DNA polymerase 3 forms dsDNA or makes a complementary DNA strand ; reverse transcriptase 4 uses mRNA (as a template) to make, cDNA / complementary (ss)DNA ; R converts © Cambridge University Press & Assessment 2024 Page 10 of 20 4(a)(ii) any three from 3 1 for transcription factor(s) to bind ; 2 for RNA polymerase to bind ; 3 (so) gene is, expressed / switched on / activated / transcribed ; 4 to, increase / control, transcription of the, gene of interest / marker gene; 5 to cause transcription with a specific environmental change ; A inducible promoter 6 AVP ; e.g. choose promoter to give transcription in, all tissues / all developmental stages 4(b) plasmid X - no insulin because the gene is, inserted backwards / the wrong way around ; 3 plasmid Y - produces insulin because the gene, is inserted the correct way around / AW ; plasmid Z - no insulin because, the gene was not inserted / the plasmid closed up / it is a non-recombinant plasmid ;

5(a) crossing over ; A chiasma formation 1 © Cambridge University Press & Assessment 2024 Page 11 of 20 5(b)(i) any three from: 3 1 mutation occurred a long time ago or someone in original population had mutation or mutation in common ancestor ; 2 ref. to. founder effect ; 3 (original / current) population is small ; 4 idea that much of the population is closely related or small gene pool / low genetic diversity ; A inbreeding 5 ref. to isolated (population) ; 6 (caused) increase in frequency of, mutation / 999del5 / BRCA2 allele ; 5(b)(ii) any three from: 3 1 reduce worry if negative ; (if positive) 2 lifestyle changes / described ; 3 early treatment / breast removal / can have frequent checks ; 4 informed decision about having children ; 5 ref. to counselling ; 6 could lead to lower death rates from breast cancer ; © Cambridge University Press & Assessment 2024 Page 12 of 20 5(b)(iii) any one from: 1 1 only screen for mutations that occur with high frequency in a population (as opposed to hundreds of mutations) ; 2 cost effective ; 3 early diagnosis / early treatment / targeted treatment ; 4 identifies mutation known to increase the risk of developing breast cancer (as opposed to a neutral mutation) ; 5 could lead to lower death rates from breast cancer ; 5(c)(i) any two from: 2 1 it, inserted / deleted / replaced, DNA (in, Lcn2 / regulatory sequence) ; 2 (so) transcription of, Lcn2 / gene, prevented ; 3 (replaced mutated section of DNA) with correct sequence ; 5(c)(ii) only specific, sites / sequences, (on DNA targeted) 1 or target site on DNA only found in Lcn2 ;

8(a) any three from: 3 1 make cDNA from, messenger RNA / mRNA ; 2 using reverse transcriptase ; 3 synthesise (gene chemically) from nucleotides / join nucleotides ; 4 (using known) amino acid / nucleotide, sequence from database ; 8(b) 3 role in genetic DNA ligase DNA engineering polymerase joins two sections of sugar phosphate ✓  ; backbone in DNA adds a gene to a plasmid ✓  ; adds free activated DNA nucleotides to a  ✓ ; polynucleotide 8(c) 1 90–98oC – DNA, denatures / strands separate ; 3 2 50–65oC – primers, bind / base pair / anneal (to DNA) ; 3 68–75oC – Taq / DNA, polymerase, makes, DNA / (new) strand ; © Cambridge University Press & Assessment 2024 Page 13 of 15

3(a) any three from: 3 1 manipulation of, genetic material / gene / DNA or described ; 2 ref. to gene / allele, transfer (into, cell / organism) or described ; 3 expression of gene ; 4 (named) phenotype modified / (named) protein produced ; 5 AVP ; e.g. ref. to gene editing / produce GMO 3(b)(i) any three from: 3 1 add, healthy / normal / correct / functional, gene / allele, to virus ; 2 inject virus into eye ; 3 gene integrated into (eye cell) genome / DNA ; 4 gene / allele, expressed to produce functioning, protein / enzyme ; 5 AVP ; e.g. adeno-associated virus / AAV voretigene neparvovec (drug) 3(b)(ii) any one from: 1 1 easily accessible / easy to inject ; 2 low risk of immune response ; 3 (eye small in size so) small amount of gene therapy treatment needed / AW ; © Cambridge University Press & Assessment 2024 Page 7 of 19 3(c)(i) any three from: 3 1 (overall) improvement in acuity of both eyes or (overall visual) acuity of both eyes becomes more negative ; 2 treated eye, has more improved acuity / has more negative (visual) acuity ; ora 3 ref. to anomalous result at month 9 / result that does not fit the pattern at month 9 ; 4 data quote – values of one eye at two months or values of both eyes at one month ; time / change in visual acuity / au months eye not eye treated treated 0 0.00 0.00 1 -0.12 -0.20 2 +0.02 -0.40 3 0.00 -0.50 4 -0.13 -0.52 5 -0.22 or -0.23 -0.52 6 -0.15 -0.54 7 -0.12 -0.50 9 -0.15 -0.33 10 -0.08 -0.52 12 -0.12 -0.54 © Cambridge University Press & Assessment 2024 Page 8 of 19 3(c)(ii) any three from: 3 1 mutated DNA is, deleted / removed / cut out or DNA replaced with normal DNA ; Ignore exon X is deleted as this is mRNA not DNA Reject gene deleted / cut out 2 specific (locations) / between exon 26 and exon 27, (in the genome) ; 3 functional protein / CEP290, now made OR correct functioning of photoreceptors ; 4 acts on person’s own DNA ; 5 AVP ; e.g. STOP codon no longer present Question Answer Marks

8(a) any three from: 3 1 make cDNA from, messenger RNA / mRNA ; 2 using reverse transcriptase ; 3 synthesise (gene chemically) from nucleotides / join nucleotides ; 4 (using known) amino acid / nucleotide, sequence from database ; 8(b) 3 role in genetic DNA ligase DNA engineering polymerase joins two sections of sugar phosphate ✓  ; backbone in DNA adds a gene to a plasmid ✓  ; adds free activated DNA nucleotides to a  ✓ ; polynucleotide 8(c) 1 90–98oC – DNA, denatures / strands separate ; 3 2 50–65oC – primers, bind / base pair / anneal (to DNA) ; 3 68–75oC – Taq / DNA, polymerase, makes, DNA / (new) strand ; © Cambridge University Press & Assessment 2024 Page 13 of 15

3(a)(i) any four from: 4 1 DNA polymerase ; 2 synthesises, complementary / new, DNA strand ; 3 binds to primers on (target) DNA ; 4 adds (DNA) nucleotides to the end of primers or used in extension stage ; 5 (optimum) working temperature of 72 °C ; A 70–75 °C 6 thermostable / does not denature at 95 °C ; 7 (so) can be used for many PCR cycles / does not need replacing ; 8 AVP ; e.g. forming phosphodiester bonds (between adjacent nucleotides) 3(a)(ii) (child) 2 and (child) 3 ; 1 3(a)(iii) any three from: 4 1 separates DNA fragments of different, sizes / lengths / mass ; 2 DNA fragments are negatively charged ; 3 (so) DNA fragments move (from cathode) to anode ; 4 smaller DNA fragments migrate, faster / further ; ora 5 DNA fragments from, normal (MT-RNR1) gene travels shorter distance ; ora 3(b) horizontal transmission / transfer plasmids / conjugation / transduction / transfection / transformation ; 1 © Cambridge University Press & Assessment 2025 Page 9 of 19

3(a) dominant ; 2 3 / daughter, has disease but, 2 / father, does not or 3 / daughter, could not have the disease if allele were recessive ; 3(b) any three from: 3 1 founder effect ; 2 allele / variegate porphyria, present in, migrants / settlers / founding population ; 3 higher frequency than in, Dutch / Europeans / original population ; 4 genetic drift has large effect in small, population / gene pool ; 5 inbreeding / migrants married within their own population ; 6 high frequency of allele maintained over, time / generations ; 7 AVP ; © Cambridge University Press & Assessment 2025 Page 9 of 17 3(c) any four from: 4 1 use mRNA (from person’s cells) to make, cDNA / ssDNA ; 2 add fluorescent, label / tag / dye / chemical / marker, to (this ss) DNA ; 3 cDNA / ssDNA, hybridises with / binds to / complementary base pairs with, probe(s) / microarray ; 4 fluorescence shows, disease / mutant, gene / allele, expression / transcription ; 5 AVP ; 3(d) any one from: 1 1 find out / diagnose, person’s disease ; 2 so can, choose / develop, right treatment ; 3 global, research resource / access ; 3(e) any three from: 3 1 change from T to C or replacement / substitution, of T, with / by, C or substitution of C for T ; 2 functional / working / correct / normal, enzyme / protein, produced ; 3 gRNA, is specific to / only finds / just alters, CEP /disease / mutant, allele / gene or gRNA does not bind to genes other than CEP ; 4 AVP ; © Cambridge University Press & Assessment 2025 Page 10 of 17

5(a) any four from: 4 1 find, nucleotide / base / gene / DNA, sequence ; 2 from database / using bioinformatics / from gene library ; 3 make the gene (chemically) using nucleotides ; 4 extract mRNA from cell, making the protein / expressing the gene ; 5 use reverse transcriptase (with mRNA) to make cDNA ; 6 use DNA polymerase (with cDNA) to make dsDNA ; 7 cut out / extract / isolate, the gene from DNA ; 8 using restriction enzyme ; © Cambridge University Press & Assessment 2025 Page 14 of 25 5(b) any three from: 3 ora for animal insulin 1 large scale supply / supply can match demand ; 2 no / less, likely to cause, immune / allergic, response or fewer side-effects ; 3 faster to act / smaller dose needed ; 4 no / less, likely for (insulin) tolerance to occur ; 5 no / less, risk of infection / disease ; 6 no / less, ethical / religious objections or suitable for, vegetarians / vegans ; 7 AVP ; e.g. cheaper to produce / easier to purify 5(c) DNA from two different sources (joined together) 1 or DNA from (human) gene joined to DNA from, bacteria / plasmid ; © Cambridge University Press & Assessment 2025 Page 15 of 25 5(d) any four from: 4 1 find, nucleotide / base / gene / DNA, sequence (of human insulin gene) ; 2 from database / using bioinformatics / from gene library ; 3 gene editing ; 4 insertion / deletion / replacement, of nucleotide(s) ; 5. at specific sites (of the gene) ; 6 (results in) changes to the, (DNA) triplet / codon ; 7 (so codes for a) different amino acid ; 8 AVP ; e.g. detail of gene editing / CRISPR / Cas9 © Cambridge University Press & Assessment 2025 Page 16 of 25

5(a) any three from: 3 1 cDNA has, no introns / only exons or genomic DNA has introns (and exons) ; 2 introns are non-coding sequences / exons are coding sequences ; 3 bacteria cannot, remove introns / carry out splicing ; 4 with cDNA, functional mRNA is made / translation occurs or with genomic DNA, functional mRNA is not made / translation does not occur ; 5(b)(i) bond together / anneal, with hydrogen bonds ; 2 formation of phosphodiester bonds / joins sugar phosphate backbone ; 5(b)(ii) 1 so RNA polymerase can bind ; 2 2 so, transcription / gene expression, occurs ; © Cambridge University Press & Assessment 2025 Page 13 of 20 5(c) any three from: 3 1 marker gene is added to plasmid ; 2 positioned downstream of promoter ; 3 positioned alongside, GOI / insulin gene; 4 when marker gene is expressed fluorescent proteins are made ; 5 ref. to (fluorescent proteins) fluoresce / glow, with exposure to, UV / blue, light ; 6 shows which, bacteria / cells, are transformed / AW ; 5(d) any two from: 2 advantages of using yeast: 1 easier / cheaper, to culture yeast cells ; 2 more productive / higher productivity ; 3 easier, to extract / processing / to purify, (insulin) ; 4 yeast cell similar to β-cells / named example ; e.g. have Golgi apparatus Question Answer Marks

5(a) any five from: 5 Allow any temperature within the ranges given 1 denaturation at 90–98 °C ; 2 breaks hydrogen bonds (in DNA) to, produce single strands / separate the (two) strands ; 3 annealing at 50–65 °C ; 4 (so that) primers, anneal / bind, (ss)DNA / complementary bases ; 5 (to provide) binding site / starting point (for Taq polymerase) ; 6 extension or elongation at 65–75 °C ; 7 Taq polymerase joins, (free) nucleotides / dNTPs, to (single) strands or Taq polymerase synthesises, complementary / new, strand (of DNA) ; © Cambridge University Press & Assessment 2025 Page 18 of 27 5(b)(i) any four from: 4 bacteria = E.coli and virus = herpes simplex throughout 1 extract / isolate / cut, DNA (sequences) using restriction enzyme or make DNA (sequences) using mRNA using reverse transcriptase or make DNA (sequences) using nucleotides ; 2 use DNA ligase to join together (the two sequences of) DNA (of bacteria and virus) ; 3 add promoter ; 4 add, tTav / recombinant DNA / gene, to, vector / virus / liposome ; 5 infect egg with virus or (micro)injection into egg ; A gene gun / DNA gun 6 virus adds, tTav / recombinant DNA / gene, into genome (of egg / A. stephensi) ; 5(b)(ii) any one from: 1 1 idea that prevents, transcription factor, functioning / binding to promoter ; R repressor proteins / operator 2 stops RNA polymerase from binding to, DNA / promoter ; 5(b)(iii) (genetically modified males) develop into adults / survive beyond the larval stage ; 1 © Cambridge University Press & Assessment 2025 Page 19 of 27

8(a) any four from: 4 1 (Liberty Link soybean / it, is) not harmed by / not killed by / resistant to, herbicide / glufosinate ; 2 herbicide / glufosinate, kills, weeds / unwanted plants ; 3 reduces / removes / less / no, competition (with, weeds / unwanted plants) ; 4 ref. to (sun)light / water / (named) soil minerals ; 5 higher yield or more crop, harvested / produced ; 6 AVP ; 8(b)(i) restriction, enzyme / endonuclease ; 1 8(b)(ii) (DNA) ligase ; 1 8(c) any three from: 3 some / other / 21, countries: 1 may, have, unsuitable / described problem in, climate / weather / soil ; 2 no regulatory approval / may have banned (GM / Liberty Link) ; 3 may have, (activist) groups / people, opposed to GM crops ; 4 may not have land space available ; 5 may have banned, herbicide / glufosinate ; 6 AVP ; © Cambridge University Press & Assessment 2025 Page 16 of 18

5(a) any four from: 4 mark as pairs Name 1 dNTPs / DNA nucleotides ; Explanation 1 to, anneal / bind, to complementary bases ; Name 2 Taq polymerase ; Explanation 2 to make, phosphodiester bonds / the sugar phosphate backbone / double-stranded DNA / a complementary strand of DNA or ref. to functioning at higher temperature / does not denature at the higher temperature / is thermostable ; Name 3 buffer ; Explanation 3 to provide, optimum / suitable / constant, pH for, polymerase / DNA or prevents, denaturation of polymerase / damage to DNA ; 5(b)(i) any two from: 2 1 (DNA ladder) compared to (other fragments) ; 2 ref. to (estimate) length of (DNA) fragment / to identify the fragment number ; 3 ref. to show electrophoresis worked correctly ; © Cambridge University Press & Assessment 2025 Page 15 of 23 5(b)(ii) any three from: 3 1 (PCR) amplifies / makes many copies of, DNA (fragments) ; 2 (PCR) ref. to selecting fragments, small enough / less than 1000 bp / not more than 916 bp (for sequencing) ; 3 (electrophoresis) separate the (DNA) fragments ; 4 (electrophoresis) confirms / identifies, fragment lengths / fragment number / PCR worked correctly ; 5(c) (235 =) 3.4  1010 ; 1 5(d) any four from: 4 1 child may have disease when, neither parent has the disease / no family history ; 2 early, detection / treatment (for gene therapy to work) ; 3 improve, quality of life / life expectancy ; 4 ref. to informs family planning (for future pregnancies) ; 5 idea that it does not involve additional sampling ; 6 (screening is) expensive ; 7 treatment / gene therapy, expensive ; 8 test may not always be accurate ; 9 long-term effect of treatment, unknown / negative ; © Cambridge University Press & Assessment 2025 Page 16 of 23

8(a) any four from: 4 1 (Liberty Link soybean / it, is) not harmed by / not killed by / resistant to, herbicide / glufosinate ; 2 herbicide / glufosinate, kills, weeds / unwanted plants ; 3 reduces / removes / less / no, competition (with, weeds / unwanted plants) ; 4 ref. to (sun)light / water / (named) soil minerals ; 5 higher yield or more crop, harvested / produced ; 6 AVP ; 8(b)(i) restriction, enzyme / endonuclease ; 1 8(b)(ii) (DNA) ligase ; 1 8(c) any three from: 3 some / other / 21, countries: 1 may, have, unsuitable / described problem in, climate / weather / soil ; 2 no regulatory approval / may have banned (GM / Liberty Link) ; 3 may have, (activist) groups / people, opposed to GM crops ; 4 may not have land space available ; 5 may have banned, herbicide / glufosinate ; 6 AVP ; © Cambridge University Press & Assessment 2025 Page 16 of 18

3(a) any five from: 5 1 restriction endonuclease ; 2 (RE) cuts, bacterial / herbicide-resistance, gene / DNA ; 3 (RE) cuts a, plasmid / vector ; 4 DNA ligase joins, new / bacterial / foreign, gene to, plasmid / vector ; 5 ref. to joining / adding, of promoter ; 6 (promoter / regulatory sequence) ensures expression of (new / bacterial / foreign / prokaryotic) gene ; 3(b) 73 / 100  123.5 2 or 90.155 million ; (90.155  2 =) 180.31 million ; © Cambridge University Press & Assessment 2025 Page 9 of 17 3(c) any four from: 4 positive implications: 1 more food / higher yield (per hectare) ; 2 (farmers) use less, insecticide / pesticide ; 3 cheaper food prices for consumers ; 4 less land needed to grow food leaves more for, biodiversity / conservation ; 5 improved food nutritional value ; negative implications: 6 food allergies ; 7 greater quantity of herbicide residue on food ; 8 (evolution of) resistance in, insects / weeds / fungi / pests ; 9 pollen drift to / cross-breeding with, organic / non-GM / conventional, crops ; 10 GM crops may become invasive weeds ; 11 consumer mistrust / GM food must be clearly labelled ; Question Answer Marks

3(a) HTT / huntingtin ; A IT15 2 huntingtin ; 3(b)(i) any one from: 1 1 (close) family history (of Huntington’s) ; 2 adults that have (early) symptoms of Huntington’s ; 3(b)(ii) any two from: 2 1 adult-onset disease / symptoms generally occur later in life ; 2 adults can make lifestyle choices ; e.g. whether or not to have children 3 implications of positive result ; e.g. at-risk parent may not have taken test e.g. wait to see if parent has Huntington’s 4 psychological impact / children not able to give (informed) consent / AW ; ora 3(c) A DNA fragments or bands for alleles throughout 4 1 adult A has no alleles with more than 35 (CAG) repeats ; ora 2 adult B has one allele between 35 and 40 (CAG) repeats ; 3 adult C and adult D have one allele with more than 40 (CAG) repeats ; 4 adult D has more (CAG) repeats than adult C ; © Cambridge University Press & Assessment 2026 Page 11 of 25 3(d) any three from: 3 1 Huntington’s disease is (autosomal) dominant ; 2 addition of normal allele only corrects recessive disorders or dominant allele cannot be, masked / switched off ; 3 gene therapy does not remove the, mutated / dominant, allele ; 4 not able to replace, nerve / brain cells ; 5 correct type of stem cells may not be available ; A correct ref. to viruses © Cambridge University Press & Assessment 2026 Page 12 of 25

6(a) 3 name type name of function of of gene of gene protein produced protein produced binds to operator lacI regulatory ; repressor protein to prevent RNA polymerase binding to promoter hydrolyses / breaks down / converts, lactose to glucose and galactose ; lacZ structural -galactosidase A converts lactose to allolactose membrane transport protein lacY ; structural lactose permease to increase cellular uptake of lactose acetylates galactoside lacA structural transacetylase sugar residues to detoxify the cell © Cambridge University Press & Assessment 2026 Page 17 of 25 6(b) ora for animal insulin 5 any five from: 1 large scale supply / supply can match demand ; 2 no / less, chance of immune / allergic response or fewer side effects ; 3 fast to act / smaller dose needed ; 4 not / less, likely for (insulin) tolerance to occur ; 5 no / less, risk of, infection / disease ; 6 no / fewer, ethical / religious, considerations or suitable for, vegans / vegetarians ; 7 cheaper to produce / can control time of production / easier to purify ; © Cambridge University Press & Assessment 2026 Page 18 of 25

8(a)(i) any three from: 3 CON receptor cell confused with receptor protein once then ECF 1 detect stimuli ; 2 receptor potential ; 2 ALLOW generator potential 3 impulse / action potential, in sensory neurone ; 3 DO NOT ALLOW pass, receptor potential / stimulus, to sensory neurone 4 ref. to chemoreceptors on (moth) antenna ; 5 act as transducers ; 5 ALLOW description e.g. convert energy from one form to another / convert (named) stimulus energy to electrical energy 8(a)(ii) any three from: 3 IGNORE gene expression 1 switch gene, on / off ; 1 ALLOW gene switching 2 transcription factor ; 2 ALLOW activator / repressor 3 allows / stops, RNA polymerase to, act / bind ; 4 gene for enzyme to make, lipid / scent (chemical) ; 5 AVP ; 5 e.g. light detected / light receptor / phytochrome e.g. clock genes e.g. negative feedback e.g. mRNA / protein, degradation (→ daily cycle) 8(b) A: mRNA ; 3 A: ALLOW messenger RNA B: cDNA / ssDNA ; B: ALLOW complementary / single-stranded, DNA C: (ss DNA) probe / reporter / oligo ; C: IGNORE complementary © Cambridge University Press & Assessment 2026 Page 20 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/

10(a) any three from: 3 IGNORE genetic screening 1 change / manipulate / alter / modify, (organism’s) 1 IGNORE genetic information DNA / genetic material / genome ; 1 ALLOW recombinant DNA in organism context 1 ALLOW adjust for ‘change’ 2 to, change / modify, (organism’s) 2 ALLOW traits / features, for ‘characteristics’ characteristics / phenotype ; 3 new / different / functional, protein produced ; 4 ALLOW gene editing / edit genes 4 transfer / add / insert, gene / allele / DNA (into a recipient 4 ALLOW delete / replace, gene (in GMO) organism) ; © Cambridge University Press & Assessment 2026 Page 22 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/ 10(b) any six from: 6 prepare the vector 1 (normal / dominant) allele / gene, for ADA / adenosine 1 ALLOW IL2RG / DCLRE1C, for ‘gene for ADA’ deaminase ; 2 inserted into, vector / virus ; 2 ALLOW retrovirus / lentivirus 2 IGNORE adenovirus / AAV / plasmid 3 virus modified so it cannot replicate ; 3 ECF if incorrect virus named e.g. adenovirus / AAV obtain and modify patient cells 4 get (haemopoietic / lymphoid) stem cells from (patient) 4 ALLOW get T, lymphocytes / cells, from blood bone marrow ; 5 ALLOW idea of inserting, virus / vector, into 5 mix / culture, (engineered) vector, with, patient’s / stem, patient’s / stem, cells (in vitro / ex vivo) cells (in vitro / ex vivo) ; 5 ALLOW if patient cells stated to be T cells 6 drug to increase stem cells (in bone marrow) before mp 4 OR drug / chemotherapy / radiotherapy, to kill stem cells (to make space) before mp 7 ; return modified cells to patient 7 reintroduce (GM / transgenic) cells to, patient / bone 7 ALLOW patient T cells returned to blood marrow / blood ; 8, 9 gene, cloned in / taken from, GM bacteria 8 AVP ; multiply transformed, patient / T / stem, cells 9 AVP ; T-lymphocytes / T-cells, produce ADA (protein / enzyme) © Cambridge University Press & Assessment 2026 Page 23 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/

4(a) 3 1. (deliberate) manipulation / changing, of, DNA / genetic material / genome ; 2. to, modify / improve / add, (named) characteristics of, organism / crop / plant ; 3. ref. to add / delete / replace, gene / allele (into crop) or gene editing ; A CRISPR 4(b) any answer between 295 and 305 ; © Cambridge University Press & Assessment 2026 Page 11 of 23 ( 1 7 0 4 − 2 4 . 5 2 . 5 ) 2  100 If incorrect answer max 1 mark for this equation 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/ 4(c) any five from: 5 1 idea of increase / high, productivity / yield / food quantity ; A named example 2 improve (named) quality ; 3 ref. to herbicide / weedkiller, tolerance / resistance ; 4 reduces / no, competition from weeds or so crops get more, light / water / AW ; 5 ref. to insect / pest, resistance ; 6 less / no, crop damage or less food wastage ; 7 ref. to economic advantage ; 8 tolerance to name factor ; e.g. disease / environmental extreme / frost / high temperatures / windy / less fertile soil © Cambridge University Press & Assessment 2026 Page 12 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/

3(a) 1 idea of use primers, specific / complementary / AW, to mutant (HBB) allele ; 4 2 denature DNA / separate DNA into (two) strands ; 3 annealing / binding, of primers ; 4 DNA, elongation / extension / synthesis / replication ; 3(b) homozygous normal = 3 2 homozygous mutant = 1 heterozygous = 2 and 4 one correct = one mark all three correct = two marks ; ; 3(c) any four from: 4 1 take DNA sample from cell (of person) ; 2 make DNA single-stranded ; 3 add fluorescent, label / tag / dye / chemical, to the DNA (sample) ; R marker gene 4 microarray / chip, has (ss)DNA, probe(s) for mutant (HBB) allele ; 5 (ss)DNA, hybridises with / binds to / complementary base pairs with, probe(s) (on microarray) ; 6 fluorescence shows presence (of mutant allele) ; 7 AVP ; e.g. ref. to wash off excess (ss)DNA after hybridisation UV light / laser (scan), to see fluorescence © Cambridge University Press & Assessment 2026 Page 10 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/

8(a) any three from: 3 1 DNA (sample) ; 2 primers ; 3 (free) DNA nucleotides ; 4 heat-stable DNA polymerase / taq polymerase ; 5 buffer solution ; 8(b) any seven from: 7 1 denaturation at 90–98 C ; 2 breaks hydrogen bonds (in DNA) ; 3 to, produce single strands / separate the (two) strands ; 4 annealing at 50–65 C ; 5 (so that) primers, anneal / bind, (ss)DNA / complementary bases ; 6 extension / elongation, at 65–75 C ; 7 Taq polymerase binds to primer or primer provides, binding site / starting point, for Taq polymerase ; 8 Taq polymerase joins, (free) nucleotides / dNTPs, (to single strands) ; 9 to synthesise, complementary / doubled stranded / new, DNA ; © Cambridge University Press & Assessment 2026 Page 19 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/