2021TrialShort answer

Q30 (c)

3 marks

Question

The data below examines the changes in allele frequencies at a single locus with two alleles B and b in two very large populations of rabbits due to natural selection. It is known that a variety of genetic traits affect the survivability of rabbits in the wild, as well as in breeding populations. One such trait is furless rabbits (naked bunnies). This trait was first discovered in England by W.E. Castle in 1933. The furless rabbit is rarely found in the wild because the cold English winters are a selective pressure against it. The dominant allele for normal fur is represented by B and the recessive allele for no fur is represented by b.

In rabbits, an unlinked second gene controls the length of fur, if any. Long hair (L) is dominant over short hair (l). A long-haired rabbit was crossed with a furless rabbit to produce many offspring, all of which have fur. One-quarter of the offspring are short-haired rabbits. Deduce the genotypes of the two parent rabbits. Show working.

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Solution

Criteria	Marks
• Deduces the short-haired rabbits, the B/b and L/l alleles, and the genotypes of the parents.	3
• Any TWO of the above.	2
• Any ONE of the above.	1

Additional guidance from the source:

Bl Bl BL BL BbLl X bbLl bL BbL Bbl BbL BbL l L L L Short haired : ¼ Long haired : 3/4 bL BbL BbL BbL BbL l l L L bl Bbll Bbll BbLl BbLl

Supplied marking guidance · human reviewed

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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