Question

A male human is heterozygous for autosomal genes A and B. He is also hemizygous for haemophilic gene h. What proportion of sperms will carry abh.
a. \dfrac{1}{8}
b. \dfrac{1}{32}
c. \dfrac{1}{4}
d. \dfrac{1}{16}

Answer 1

Hint: An organism is called heterozygous when its cells contain two different alleles of a gene which is known as diploid. Heterozygous genes are represented by uppercase letters and a lowercase letter as Aa and Bb.

Complete answer:
Hemizygous is a condition when only one copy of gene or DNA sequence is present in diploid cells. Mostly males are hemizygous on sex chromosomes as they contain only one X and one Y chromosome. Autosomal gene means that the gene which is not sex chromosome and the members of an autosome pair in a diploid cell have same morphology, different from those allosome pairs which have different structures.

Male human is heterozygous for genes A and B and hemizygous for h. Which means that the genotype would be AaBbXh Y. Human males are hemizygous for h and can fall on X whereas homozygous females would fall as Xh X.? In the cross of heterozygous chromosomes A and B with hemizygous chromosome h.

The resulting gametes we can get in this is ABXh, abXh, abY, AbY, aBX, aBY, AbXh and ABY. These eight chromosomes we can get with the above cross of heterozygous chromosomes A and B and hemizygous for haemophilic gene h. Therefore the proportion of getting any of the chromosomes by a sperm will be \dfrac{1}{8}.

Hence, the correct answer is option (A).

Note: Mother passes the alleles of sex linked traits into both sons and daughters. Majority of the sex linked traits are recessive alleles and are more apparent in males than in females.