Question

2. Hemophilia is a recessive X-linked disease in humans. Use a Punnett square to predict the genotypes

and phenotypes of children born to a father who is normal and a woman who is a carrier or
heterozygous for this condition. Let X represent the normal allele and xh represent the allele for
hemophilia.

Answer 1

25% normal females, 25 % normal males, 25% carrier males, 25% hemophilic males.

Step-by-step explanation:

For a X linked recessive trait to occur, both the X alleles should be homozygous recessive in females. As males carry only one X chromosome, a single recessive gene would cause the disease or trait in them.

When a father who is normal will be crossed with a mother who is carrier or hemophilia then

25% of the females will have a normal genotype (XX) and phenotype.

25% of the males will have a normal genotype (XY) and phenotype.

25% of the males will have hemophilia, the genotype will be (XhY).

25% of the females will be carriers having genotype (XXh) and will have normal phenotype.