Day 1: The Journey Begins
Meiosis and Mitosis
Shortly after release from the ovary but before
the outer layers of the egg are added, the nucleus
undergoes meiosis to prepare it for fertilization.
Only one of the cells produced during meiosis goes
on to become the embryo while the rest disappear.
The ovum now contains a haploid number of
chromosomes and is ready to be fertilized by a
sperm. If a sperm from a rooster is present,
fertilization can take place. The resulting
zygote begins simple cell division called mitosis.
By the time the egg is laid, the embryo has
reached the blastoderm stage. Whether the egg is
fertilized or not, it will continue down the
oviduct to be covered by albumen and a shell
before it is laid. Fertilized eggs go on to
become chicks; unfertilized eggs go on to become
Text and graphic by Janet Sinn-Hanlon
- Page 9 of 12 -