Question

A human male is heterozygous for autosomal genes ‘A’ and ‘B’. He is also hemizygous for the haemophile gene ‘h’. What percentage of sperms will carry ‘abh’ genotype?
A. 12.5%
B. 0.31%
C. 75%
D. 0%

Answer 1

Hint: Heterozygous is a genetic condition in which an individual inherits different alleles of the same gene from the two parents, and when an individual inherits similar alleles of the same gene from the two parents is called homozygous. For example, ‘A’ and ‘a’ are different alleles of the gene A. So, (AA or aa) will be homozygous and (Aa) will be heterozygous.

Complete answer:
Haemophilia is a sex-linked recessive disorder. The haemophilic gene is present on the X-sex chromosome. Males have one X chromosome and one Y chromosome.
Given in the question: The male is heterozygous for ‘A’ and ‘B’ and hemizygous for haemophilic gene‘h’. Then, the human male genotype will be $AaBb{X^h}Y$. X-chromosome will have ‘h’ gene whereas Y sex chromosome will be empty for haemophilic gene’h’ as it is only linked to X-sex chromosome.
 The gamete will be formed from the above mentioned ($AaBb{X^h}Y$) will be $ab{X^h}$, abY, $AB{X^h}$, ABY, $Ab{X^h}$, AbY, $aB{X^h}$ and aBY. It is, therefore, the total number of male gametes (sperm) carrying $aB{X^h}$ is 1. Thus, out of 8 gametes, 1/8 is abh or 12.5%.
Thus, option A. 12.5% is the correct answer.

Additional information:
The genotype is the genetic constitution of an organism. AA or Aa are the genotypes of the
organism regarding the particular pairs of alleles. Genotype can be homozygous and
heterozygous genotype.

Note:
When a human male is heterozygous for autosomal gene A and B and also a hemizygous for haemophilic gene h then his genotype will be $AaBb{X^h}Y$ as haemophilia is an X-linked recessive disorder. Out of 8 types of gametes, only 1 or 12.5 % will be abh.