Genes, Gametes, and Conception  The conception process is very
complex and important to understanding human development.
Conception begins with the fusion of an egg cell and a sperm
cell, or gametes. At birth, a female has all the immature eggs
that she will use throughout the course of her life. A male
human being starts producing sperm when he reaches puberty
(around 1,000 sperm in a second, but this rate slows as the male
ages).  Though a female is born with all her eggs, not all these
eggs will reach maturity. Approximately only 1 in 5,000 of a
female's eggs reach maturity. When an egg reaches maturity, that
egg is then able to produce offspring.  From 200 to 600 million
sperm are released in the average ejaculation but a rare few
make it to the actual egg, and only one sperm is needed to form
a zygote (or a fertilized single-celled egg, the earliest form
of human beings). As soon as that one lucky sperm begins to
penetrate the jellylike outer coating of the egg cell, the egg
becomes defensive and the sur