What is a Zygote?

The term “zygote” refers to an early stage in the development of a new organism. It is the first stage of embryonic growth and development and marks the start of the process of fertilization. A zygote is a single-celled organism that results from the fusion of two parental gametes, usually an egg and a sperm. This single cell is the basis for the development of all future cells and tissues of the developing organism.

Structure of the Zygote

A zygote is composed of the haploid chromosome set of both the egg and the sperm, the latter usually containing 23 individual chromosomes. Upon the fusion of the egg and sperm, the double-stranded chromosomes of the pair combine to form one long double-stranded chromosome structure. The zygote contains the genetic information from this structure, known as the haploid set. This haploid set is diploid, meaning it carries two complete sets of chromosomes, one from each parent and identical to each other.

Zygote Development

Once fertilized and the haploid sets are complete, the zygote will begin to divide and, in the process, produce two different cells. As the zygote continues to divide, the two sets of chromosomes will line up in this process, known as meiosis. This helps the zygote to form the different cell types that will make up the future organism. These cells will divide, differentiate and form the different tissue types, organs and organ systems, giving rise to the new organism.

The process of zygote formation, development and growth is a largely automated process governed by internal and external influences. The genes contained in the haploid set, combined with environmental influences, will help determine the growth and development of the resulting organism. The end result of this process will be the formation of a fully formed embryo, ready to be born.