Name: Sex Determination (Drosophila melanogaster)
Uploaded: 2019-07-19
Duration: 7 min 20 s
Description: Drosophila melanogaster or the common fruit fly has contributed a lot to genetics. One of them is its sex determination system with more than five types of s...

Question

A man who is red-green colour-blind marries a woman with normal vision. They have three sons and two daughters. One of the sons is red-green colour-blind. All the other children have normal colour vision. Draw a genetic diagram to suggest an explanation for this.

Accepted Answer

Colour blindness is a sex-linked recessive inheritance in which the gene responsible for this characteristic is located on a sex chromosome (X or Y). Here, a red-green colour-blind man marries a woman with normal vision in which one of their sons is colour-blind. This is a recessive character, hence, it is only expressed when there is no dominant allele of the gene. So, the woman should be heterozygous or carrier of that particular character.

The genetic diagram of the cross between a colour-blind man and a woman with normal vision (carrier) is shown below:

By this cross, all the daughters with normal vision are carriers. There is a possibility for the formation of colour-blind daughters. There is an equal chance for forming normal and diseased children.

Mary Jones and Geoff Jones Solutions for Chapter: Inheritance, Exercise 3: Questions

Mary Jones Biology Solutions for Exercise - Mary Jones and Geoff Jones Solutions for Chapter: Inheritance, Exercise 3: Questions

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