Question

A healthy woman with a color blind father married an unaffected man, and their first child, a boy, had hemophilia. Both color blindness and hemophilia are due to x-linked recessive mutations and the relevant genes are separated by 20 cM. This couple plans to have a second child. What is the probability of having: a) a boy with hemophilia (regardless of his vision) b) a color blind girl without hemophilia? c) a child with both hemophilia and color blindness? d) a child with neither hemophilia nor color blindness?

Answer 1

Consider the female who is a carrier has a set of Gene xX

And a male who is also a carrier for hemophilia having a set of Gene as xY.

Using mendels law of inheritence we find out the offsprings produced will be of,

1. xx - rescessive Gene from mother carrying color blind Gene and recessive Gene from father having hemophilia

2. Xx - normal dominant Gene and recessive Gene for color blindness

3. xY - recessive Gene for color blindness and normal gene

4. XY - normal gene

So from this we we can infere that,

a) There is no chance of having a boy with hemophilia

b)25% chance of having a colour blind girl with color blindess and 25% chance of having a girl child as carrier

c)25% of chances of having both colour blindness and hemophilia

d) XY gene has shown that the child born with neither hemophilia and color blindness is 25%