a haemophilic man marries a normal homozygous woman what is the probability that their daughter will be haemophilic?
Hemophilia is sex-linked disease. It is an X-linked recessive disorder. If gene on one X chromosome is mutant (causing the defect/ disease), then it will not express in females because females have 2X chromosomes and the wild gene (normal) on one X chromosome suppresses the effect of mutant gene on other X chromosome. While males have only one X chromosome, so mutant gene expresses in males and causes the disease.
When a haemophilic man marries a normal homozygous woman the probability that their daughter will be haemophilic is zero. This can be shown by following cross.
When a haemophilic man marries a normal homozygous woman the probability that their daughter will be haemophilic is zero. This can be shown by following cross.
Normal mother XX and affected father XHY.
| XH | Y | |
| X | XHX | XY |
| X | XHX | XY |
From the cross, it is clear that daughters produced are carriers while as males are normal.