A wildlife centre records fur colour in a population of mountain hares. Table 1 gives results from controlled crosses. Black fur is caused by allele B and w...
Question 1 Report
A wildlife centre records fur colour in a population of mountain hares. Table 1 gives results from controlled crosses. Black fur is caused by allele B and white fur by allele b. The centre needs to identify black hares that carry b before releasing animals into a snowy habitat, where white fur gives better camouflage.
| cross | number of black offspring | number of white offspring |
|---|---|---|
| black hare 1 × white hare | 19 | 21 |
| black hare 2 × white hare | 42 | 0 |
| white hare × white hare | 0 | 36 |
(a) State the genotype of a white hare. [1]
(b) Describe the evidence that black fur is dominant to white fur. [2]
(c) Give the genotype of black hare 1. Explain your answer using Table 1. [3]
(d) Give the genotype of black hare 2. Explain your answer using Table 1. [3]
(e) Suggest why releasing only white hares could reduce the long-term survival of this population. [1]
Answer Details
(a) A white hare has genotype \(bb\). [1]
(b) A black hare crossed with a white hare can produce black offspring. This shows that \(B\) masks the effect of \(b\) in a heterozygous offspring, so black fur is dominant. [2]
(c) Black hare 1 has genotype \(Bb\). It was crossed with a white hare, \(bb\), and produced approximately equal numbers of black and white offspring, 19 and 21. This is the expected pattern for \(Bb\times bb\). [3]
(d) Black hare 2 has genotype \(BB\). It was crossed with a white hare, \(bb\), and all 42 offspring were black. This is the expected result for \(BB\times bb\), in which all offspring are \(Bb\). [3]
(e) Releasing only white hares would reduce genetic variation. The population may then be less able to survive a new disease or environmental change. [1]
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