The genes for color blindness and hemophilia are both on the X chromosome and show a recombination frequency of 10%. In the pedigree shown below, the blackened symbols indicate hemophilia while the crosses indicate color blindness.
Giving the genotypes of the individuals:
The mother of the two women III-4 and III-5 would produce the following gametes:
• 0.45 – HB
• 0.45 – hb
• 0.05 – hB
• 0.05 – Hb
The woman III-4 can be either Hb/HB [0.45% chance] or Hb/hB [0.05% chance] since she received the B allele from her mother.
The chance of her being Hb/hB, would be:
If her genotype is Hb/hB, then she will produce the same gametes as her mother.
Her child has:
• A 45% chance of receiving hB
• A 5% chance of receiving hb
• A 50% chance of receiving Y chromosome from his dad
Hence, the probability that her child will be a hemophiliac son would be:
The woman III-5 can either be Hb/Hb [0.05% chance] or Hb/hb [0.45% chance] since she received the b allele from her mother.
The chance of her being Hb/hb, would be:
Her child has:
• A 50% chance of receiving the h allele
• A 50% chance of receiving Y chromosome from his dad
Hence, the probability that her child will be a hemophiliac son would be: