Question

3.3 The inheritance of fur colour in cats is sex-linked. The tortoise-shell colour of cats is a combination of black and orange fur. The allele for black fur is represented by X³ and the allele for orange fur is represented by Xº. A female cat with a tortoise-shell colour mates with an orange male cat. HINT: The sex chromosomes/gonosomes in cats are the same as in humans. 3.3.1 Use the symbols X³. X and Y to represent a genetic cross of the mating stated above. Also indicate the proportion of the F₁ phenotypes. Explain why the male kittens can never have the tortoise-shell colour. 3.3.3 Explain why the female kittens can have the tortoise-shell colour. 3.3.2 (7) (2) (2) (11)

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Answer 1

The inheritance of fur color in cats is indeed sex-linked. The tortoise-shell color is a combination of black and orange fur. The allele for black fur is represented by X³ and the allele for orange fur is represented by Xº. When a female cat with a tortoise-shell color mates with an orange male cat, the genetic cross can be represented as follows:

Xº Y

X³ X³Xº X³Y

Xº XºXº XºY

The proportion of the F₁ phenotypes would be 1:1 for females (50% tortoise-shell and 50% orange) and 1:1 for males (50% black and 50% orange).

Male kittens can never have the tortoise-shell color because they only inherit one X chromosome from their mother. Since the alleles for black and orange fur are both located on the X chromosome, male kittens can only inherit one or the other, but not both.

Female kittens can have the tortoise-shell color because they inherit one X chromosome from each parent. If they inherit the X³ allele from one parent and the Xº allele from the other parent, they will have both black and orange fur, resulting in a tortoise-shell color.

Step-by-step explanation: