a. Most of the X chromosome genes encode proteins that have no role in female sexual development. b. Heterozygous females are more severely affected by X-linked dominant disorders than heterozygous males. c. When dominant alleles are present on the X chromosome, they are expressed in a recessive manner in the hemizygous state. d. When males have the unusual condition of two Y chromosomes and are missing the X chromosome, all physiologic function remains normal.

Most of the X chromosome genes encode proteins that have no role in female sexual development is the true statement.

Explanation:

The X chromosome is composed of nearly 1500 single alleles of genes like any other gene code for a number of nonsexual functions (in both females and males) and not specifically for female sexual development. Specific male or female characteristics results from different combinations of gametes and not from a single X chromosome.

Since males have only one dominant X chromosome, if when subjected to a dominant mutation, heterozygous males will be more symptomatic to dominant X-linked disorders.

If the males have unusual YY chromosomes instead of XY, it results in chromosomal disorder leading to physiological, physical and cognitive functional changes.

a) false

b) false

c) false

d) true

Explanation:

a) X-chromosomes have all the genes for sexual characters of female child because female child receives 2 X-chromosomes.

b). Female are more affected with X-linked dominant disorders because female receive both the X chromosome from each of the parent.

c). In hemizygous state only single copy of gene in diploid cells. All males are hemizygous for genes on sex chromosome because male have only one sex chromosome as X and Y.

d). The resultant male will be having normal features of fertility only slow learning process, acne and above average height is seen.