Coat colour in cats is controlled by many genes - VCE - SSCE Biology - Question 3 - 2005 - Paper 1
Question 3
Coat colour in cats is controlled by many genes. One gene locus has many alleles, one of which is called the 'Siamese' allele (c^s). Cats homozygous for this allele ... show full transcript
Worked Solution & Example Answer:Coat colour in cats is controlled by many genes - VCE - SSCE Biology - Question 3 - 2005 - Paper 1
Step 1
A. two Siamese cats.
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Answer
Crossing two Siamese cats (both genotype c^s/c^s) would only result in offspring that are also Siamese, as they cannot carry the dominant C allele.
Step 2
B. two heterozygous black cats.
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Answer
Crossing two heterozygous black cats (C/c^s) would yield the following genotypes: 25% homozygous black (C/C), 50% heterozygous black (C/c^s), and 25% Siamese (c^s/c^s). Therefore, the ratio would not yield equal numbers of Siamese and black cats.
Step 3
C. a homozygous black cat to a Siamese cat.
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Answer
In this cross, the homozygous black cat (C/C) would only produce offspring that are black (C/c^s), resulting in no Siamese cats.
Step 4
D. a heterozygous black cat to a Siamese cat.
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Answer
Crossing a heterozygous black cat (C/c^s) with a Siamese cat (c^s/c^s) would yield a genotypic ratio of 1 black (C/c^s) to 1 Siamese (c^s/c^s), producing equal numbers of both.
