Which statement about the X chromosome is true?
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.

Question

Quizplus · Accepted Answer

The X chromosome is large and has about 1,500 single-gene alleles, most of which are not present on the Y chromosome or on any autosome. A few of these genes are specific for female sexual development, but there are also hundreds of gene alleles on the X chromosome that code for nonsexual functions for both males and females. Recessive alleles on the X chromosome are expressed as dominant in normal hemizygous males. The YY genotype with no X chromosome is not compatible with life. Heterozygous females are less severely affected by X-linked-dominant disorders than are males.

Which Statement About the X Chromosome Is True