Question

Sex-linked traits punnet squares - please help walk me through it! I’m so confused haha

Answer 1

Explanation:

a) The allele for hemophilia is Xh and that for normal is XH.

Crossing a hemophiliac male, Xh Y, with a normal female XH XH,

• XH Xh, normal carrier female
• XH Xh, normal carrier female
• XH Y, normal male
• XH Y, normal male

b) Both parents are normal and children still having hemophilia means that the mother is a carrier.

Let's see how it'll work out if we cross a normal male with a carrier female,

XH Y × XH Xh

• XH XH, normal female
• XH Xh, carrier female
• XH Y, normal male
• Xh Y, hemophiliac male

This means that the possibility of a female being normal, a carrier or not, is 100%. The possibility of a male being normal is 50% and the possibility of him being a hemophiliac is also 50%.

Thus it's possible that all 7 sons get hemophilia as each male baby has a 50% chance of having the genotype Xh Y. And it makes sense that all the females are normal. Those females could have the genotypes XH XH, or XH Xh (carriers).