Question

If mother is colour blind and father is normal then what will be the percentage of colour blind child (ale and femmale) in F1 progeny?

Answer 1

Total `50%` of the children will be coloublind.

`100%` of the males will be coloublind and none of the females will be colourblind

Explanation:

Colourblindness is an `X` linked recessive disorder,so a for a female to be colourblind,both of her `X` chromosomes must be defective,and for a male to be colourblind his only `X` chromosome has to be defective.

Below I have worked out the pedigree analysis of the given case, where `X` indicates normal `X` chromosome and `X'` indicates chromosome responsible for colourblindness.

Now see the result,out of the `4` children, both the boys are colourblind as they received the defective `X'` chromosome from their mother.

whereas,the two girls,though they received one abnormal chromosome `X'` each,but the normal chromosome from father being dominant didn't make them colourblind,but both of them are carrier of the disease,that means when they will marry there will be chance that `50%` of their sons will be colourblind.

So,here in our case `%` of colourblind among all the children in `F_1` is `2/4 *100` i.e `50`

And, among males both are colourblind(`100%`) and out of the two females no one is colourblind (`0%`)