At every age, males have a higher risk of mortality than do females. This sex difference is
most often attributed to the usual suspects: differences in hormones and life experiences.
However, the fact that XY males have only one X chromosome undoubtedly contributes to
this vulnerability, as any mutation that affects a gene on their X chromosome will affect their
only copy of that gene. On the other hand, cellular mosaicism created by X inactivation
provides a biologic advantage to females. There are 1100 genes on the X chromosome, and�…

Women can be described as genetic mosaics because they have two distinctly different
types of cells throughout their bodies. Unlike males, who have one X chromosome (inherited
from their mother), females have two X chromosomes in every cell (one from each parent).
The fathers copy works in some cells, while the mothers copy works in others. These two X
chromosomes often function differently, especially if one carries a defective gene. Much has
been written about the Y chromosome and its role in inducing maleness. This will be the first�…