Waiting
Login processing...

Trial ends in Request Full Access Tell Your Colleague About Jove

12.13: The Y Chromosome Determines Maleness
TABLE OF
CONTENTS

JoVE Core
Molecular Biology

A subscription to JoVE is required to view this content. You will only be able to see the first 20 seconds.

Education
The Y Chromosome Determines Maleness
 
TRANSCRIPT

12.13: The Y Chromosome Determines Maleness

The Y chromosome is a sex chromosome found in several vertebrates and mammals, including humans. In addition to 22 pairs of autosomes, the human males have one X chromosome and one Y chromosome. In these organisms, the presence or absence of the Y chromosome determines the development of male traits.

Evolution

Around 300 million years ago, the two sex chromosomes diverged from two identical autosomal chromosomes. Over time, the Y chromosome has lost most of its genes, shrinking in size. Today, only a small part of the Y chromosome shares sequence similarity with the X chromosome. A large scientific study on Y chromosomes in eight mammals, including monkeys, mice, rats, bulls, opossums, chimpanzees, and humans, showed 18 highly similar regions on Y chromosomes. The fact that these regions are retained in all these mammals, despite losing a large portion of Y chromosomes during evolution, shows that the genes on Y chromosomes are vital for the survival of these mammals.

Structure

The mammalian Y chromosome has three major regions. The pseudoautosomal regions on the Y chromosome share homology with the X chromosome and can undergo meiotic recombination. Thus, genes present in the pseudoautosomal regions are inherited in an autosomal rather than a sex-linked fashion. The second region is a euchromatin region designated as a Male-specific Y chromosome region or MSY. It spans 23 Mb in length and has few protein-coding genes, such as the SRY gene, a master regulator of maleness and the ZFY gene required for spermatogenesis. The third region is a heterochromatin region that contains several repetitive sequences.

Mutations and their effects

Deletions in the MSY region of the Y chromosome affect sperm development and cause male sterility. For example, deletions in the AZF gene on the long arm of the Y chromosome lead to a condition called azoospermia, where spermatozoa are not found in male ejaculate. In addition, deletions in specific regions of MSY are associated with testicular germ cell tumors (TGCTs).


Suggested Reading

Get cutting-edge science videos from JoVE sent straight to your inbox every month.

Waiting X
Simple Hit Counter