2021HSCShort answer

Q22

3 marks

Question

In a population of rabbits, black fur colour is dominant over white fur. A black rabbit, whose mother has white fur, mates with a white rabbit. Predict the phenotypic ratio for the offspring of this cross. Show your working.

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Solution

The black rabbit must be heterozygous because its mother was white: Bb. The white rabbit is bb.

Cross: Bb × bb

Offspring: Bb, Bb, bb, bb

Therefore, the phenotypic ratio is 1 black : 1 white (50% black and 50% white).

3 marks:

Predicts the correct phenotypic ratio of the offspring
Provides parental genotypes and suitable working out
Predicts the correct phenotypic ratio of the offspring

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Compare this with your working, not only your final sentence.

Syllabus alignment

Module 5 · Heredity

Genetic VariationInterpret inheritance patterns, pedigrees and Punnett squares to model genotype combinations.

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