Gce Model Questions Vol1 2020 Biology Question 40

Practice objective / multiple choice question 40 from the 2020 Gce Model Questions Vol1 Biology examination.

Gce Model Questions Vol1 2020 Biology Objective / Multiple Choice Medium Difficulty
Question 40 GCE_MODEL_QUESTIONS_VOL1 • 2020 • BIOLOGY • objective

In a plant species flower colour is controlled by two linked genes: \(A\) (red, dominant to \(a\) white) and \(B\) (blue, dominant to \(b\) yellow). The genes are on the same chromosome with a recombination frequency of 10 %. A homozygous dominant plant (\(AA\,BB\)) is crossed with a double recessive (\(aa\,bb\)). The F\(_1\) plants are self‑fertilised. (a) What are the expected phenotypic proportions among the F\(_2\) offspring? (b) What proportion of the F\(_2\) plants will have red flowers with yellow spots (genotype \(A-\,bb\))?

Answer Options

Correct Answer A. Phenotypic proportions: Red‑Blue ≈ 70.3 %, Red‑Yellow ≈ 4.8 %, White‑Blue ≈ 4.8 %, White‑Yellow ≈ 20.3 %. The proportion with genotype \(A-\,bb\) (red with yellow) is ≈ 4.8 % (0.048).
B. Phenotypic proportions: Red‑Blue ≈ 60.0 %, Red‑Yellow ≈ 10.0 %, White‑Blue ≈ 10.0 %, White‑Yellow ≈ 20.0 %. The proportion with genotype \(A-\,bb\) (red with yellow) is ≈ 10.0 % (0.10).
C. Phenotypic proportions: Red‑Blue ≈ 75.0 %, Red‑Yellow ≈ 5.0 %, White‑Blue ≈ 5.0 %, White‑Yellow ≈ 15.0 %. The proportion with genotype \(A-\,bb\) (red with yellow) is ≈ 5.0 % (0.05).
D. Phenotypic proportions: Red‑Blue ≈ 68.0 %, Red‑Yellow ≈ 6.0 %, White‑Blue ≈ 6.0 %, White‑Yellow ≈ 20.0 %. The proportion with genotype \(A-\,bb\) (red with yellow) is ≈ 6.0 % (0.06).
Correct Answer
A
Correct Option:
Phenotypic proportions: Red‑Blue ≈ 70.3 %, Red‑Yellow ≈ 4.8 %, White‑Blue ≈ 4.8 %, White‑Yellow ≈ 20.3 %. The proportion with genotype \(A-\,bb\) (red with yellow) is ≈ 4.8 % (0.048).

About This Question

This is Gce Model Questions Vol1 2020 Biology Question 40. It is one of the objective questions from the 2020 Gce Model Questions Vol1 Biology examination.

Difficulty level: Medium .

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