It is, indeed, difficult to accept as true that life begins with just a single cell. In this blog, we will learn what is a zygote, how does it shape up as a human being.
The male sex cells are known as sperm that are found in the semen ejaculated while copulating with her female partner and the female sex cells are identified as eggs. For reproduction to happen and laying the foundation of a new human life, a sperm cell has to penetrate and enter into an egg cell. This unification of the sperm cell and egg cell to form another single cell is known as a zygote.
Fertilization and Role of a Zygote
A sperm cell carries with it one part of the genetic information from the male organism. That is the reason, it is known as a haploid. The egg cell is also a haploid as it carries with it another part of the genetic information from the female organism. When the two parts meet and combine, they give the zygote a comprehensive set of chromosomes and other genetic substances from both the parents. Now that the zygote has all the genetic information needed for reproducing a baby, it is regarded as a diploid.
The process of zygote formation happens at the stage of sexual reproduction. A zygote is the result of the meeting of a sperm with an egg cell and penetrating it to enter into it. During this course of time, there are generally thousands of sperm participating in the competition among them to make an entry into the single cell.
When a sperm pierces the outermost layer of the egg, a chemical transformation takes place in the outer layer to foil the entry of any other sperm in the egg cell.
Having accomplished this, the sperm, which had entered into the egg, loses its tail and swells to make a nucleus. The nucleus, thus, formed by the sperm gets united with another similar nucleus that is formed by the egg.
This unification of the sperm and the egg nuclei give a birth to another single cell, known as a zygote. Now, the zygote has a complete set of chromosomes that carry all the genetic information of the two parents.
Subsequently, after the lapse of a few hours, the zygote starts the process of making internal division and splits itself into two cells. The two cells, thereafter, get divided into four, four into eight, eight in 16 and this goes on to make the division process continuous. This uninterrupted process of cellular divisions transforms the single cell zygote into a multi-cellular entity. The cell division process in the zygote is known as segmentation.
The Zygote, thus, transformed into a big cluster of cells is known as a morula. The morula slowly begins moving down to the Fallopian tubes and, eventually, lands in the uterus. The morula takes nearly three days to reach into the uterus. When the morula reaches the uterus, it is just a hollow cellular ball, known as a blastocyst. The cellular ball (morula) then gets implanted in the uterine lining to begin its journey of growing into a new individual.