Concept:Haemophilia is an X-linked recessive genetic disorder, so a male who inherits the affected X chromosome (
XhY) will show the disease.
Explanation:The defective gene for haemophilia is recessive and located on the X chromosome.
A male has only one X chromosome, so he needs just one copy of the recessive allele (
XhY) to be affected.
Females, having two X chromosomes, usually need two copies of the allele to show haemophilia.
From the inheritance diagram, the individual marked IV is a male carrying the affected X chromosome.
Therefore, individual IV is most likely suffering from haemophilia.
Answer:D. IV
