0654.B16.3.11 — Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1 : 1 and 3 : 1 ratios: past paper questions
Real questions on 0654.b16.3.11 — use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1 : 1 and 3 : 1 ratios
The newest 12 of 12 written questions. Open one to see it on the real paper.
- 0973/41 · May/June 2026 · Q1b(i)[2]
Complete the Punnett square in Figure 1.2 to show how maize plants with round seeds produce maize plants with wrinkled seeds. The allele for round seeds is R. The allele for wrinkled seeds is r. gametes 1 gametes 2 Figure 1.2
See it on the paper → - 0973/41 · May/June 2026 · Q1b(ii)[1]
A farmer crosses heterozygous maize plants with round seeds to produce 100 new maize plants. Predict approximately how many of these new maize plants will have wrinkled seeds.
See it on the paper → - 0973/32 · May/June 2025 · Q2c(i)[2]
Table 2.1 shows the different possible combinations of alleles, a description of the combination and the colour of the pea seeds. Complete Table 2.1. Table 2.1 combination of alleles Yy description of combination colour of pea seeds homozygous dominant yellow yellow
See it on the paper → - 0973/32 · May/June 2025 · Q2c(ii)[2]
The scientist uses plants with yellow pea seeds to produce plants with green pea seeds. Complete the Punnett square in Fig. 2.2 to show how plants with yellow pea seeds produce plants with green pea seeds. parental gametes 1 parental gametes 2 Y y
See it on the paper → - 0973/32 · May/June 2025 · Q2c(iii)[1]
State the expected ratio of seed colours from this cross. yellow pea seeds : green pea seeds
See it on the paper → - 0973/41 · October/November 2023 · Q1a(iii)[3]
The couple labelled P and Q in Fig. 1.1 decide to have another child. Complete the genetic diagram in Fig. 1.2 to calculate the percentage likelihood of this child having cystic fibrosis. parent P gametes parent Q gametes percentage likelihood of child having cystic fibrosis. Fig. 1.2
See it on the paper → - 0973/31 · May/June 2022 · Q4a(iii)[1]
State the ratio of smooth peas to wrinkled peas from Fig. 4.2. smooth : wrinkled
See it on the paper → - 0973/41 · May/June 2022 · Q4a(iii)[1]
State the probability of two parents with the genotypes TT having a child with Tay-Sachs disease.
See it on the paper → - 0973/31 · October/November 2021 · Q7a(ii)[1]
State the two possible genotypes of pea B. and
See it on the paper → - 0973/31 · October/November 2021 · Q7b(i)[1]
Complete the genetic diagram in Fig. 7.1 to show the expected genotypes of the offspring. parental gametes G parental gametes g G g Fig. 7.1
See it on the paper → - 0973/31 · October/November 2021 · Q7b(ii)[1]
State the percentage chance of the parent plants in Fig. 7.1 producing offspring that have the genotype gg.
See it on the paper → - 0973/32 · May/June 2020 · Q4a(i)[2]
Complete Fig. 4.1 to show the probability of the offspring of cross 2 developing Huntington’s disease.
See it on the paper →
What examiners said
The writing of the homozygous genotype was generally well done. However, many candidates repeated homozygous dominant for the description of Yy.
— Examiner report, May/June 2025, 0973/32 Q2(c)(i) (Cambridge)
There were a significant number of very clear, well-presented answers given. Others were evidently not familiar with the use of a Punnet square. This was shown by the use of phenotypes or genotypes instead of alleles in the gametes.
— Examiner report, May/June 2025, 0973/32 Q2(c)(ii) (Cambridge)
Most candidates tried to use their Punnet square to answer this question. Common mistakes were to state that the Yy genotype would give green peas or to add up the number of Y and y alleles and give this as the ratio rather than the phenotypes.
— Examiner report, May/June 2025, 0973/32 Q2(c)(iii) (Cambridge)
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