Also located on the X chromosome of a cat is a gene that codes for deafness. This gene is recessive. A black female cat that is heterozygous for deafness (Dd) is crossed with a orange male cat that is not deaf. Show the cross. What are the phenotypes of the offspring and in what proportion? Hint: place two letters on the X chromosome in your cross. (You will need to use two superscript letters on your X chromosome)

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Biology

Josh Koch

11 July, 15:50

Also located on the X chromosome of a cat is a gene that codes for deafness. This gene is recessive. A black female cat that is heterozygous for deafness (Dd) is crossed with a orange male cat that is not deaf. Show the cross. What are the phenotypes of the offspring and in what proportion? Hint: place two letters on the X chromosome in your cross. (You will need to use two superscript letters on your X chromosome)

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Cujo · Answer 1

This gene is an X linked recessive trait, thus for it to be expressed in the females, it has to be in the homozygous recessive form (both X chromosomes will carry this trait dd). For males, only one copy which is in the recessive condition is needed for it to be expressed. Thus, a cross between

female male

XDXd x XDY

XD Y

XD XDXD XDY

Xd XDXd XdY

the offspring phenotype: normal females: 1/2

normal male: 1/4

deaf male: 1/4