How Many Types of Sex Chromosomes do Humans Have

Introduction

Humans have 2 types of sex chromosomes that are X and Y-chromosomes. Chromosomes are present in every nucleus of the cell. Chromosomes generally contain DNA organised into the genes. Genes are responsible for transferring genetic information from parent to child. Every characteristic of a child i.e hair colour, eye colour, height and many more is decided by genetic material only. Each normal cell has 23 pairs of chromosomes i.e 46 chromosomes. The chromosomes which are responsible for the determination of the sex in the human body are called the “Sex Chromosomes” or “Allosomes”. Out of 23 pairs, 22 pairs i.e 44 chromosomes are the same and the remaining two are allosomes. In mammals or Human beings, there are two types of chromosomes- An X chromosome and a Y chromosome.

The difference between the X Chromosome and Y Chromosome

Below the centre, the structure of both chromosomes is the same hence, it is called the Homologous region and the upper part is known as the Non-Homologous region.

Determination of Sex

Sex determination is a system in which the zygote is formed by the mixing of the egg and the sperm. When the zygote is formed the sex has already been determined. It depends on whether at the time of fertilisation the Chromosomes have a XX combination or an XY combination.

The eggs from the female have 23 chromosomes all of which are the same i.e X chromosome. Sperm has 23 chromosomes out of which 22 are X and the last one may be X or Y. They both combine to form a new cell or zygote and have 23 pairs of chromosomes.

The zygote which has the XX chromosome turns out to be the boy and the zygote which has the XY combination turns out to be the girl.

Importance of Chromosomes Pairing

Meiosis is the process in which the eggs and sperm combine but sometimes, there may be abnormalities. These abnormalities may be due to deletion, inversion, duplication or translocation of chromosomes. This may cause trisomy where the baby may have an extra chromosome or monosomy where the baby may have fewer chromosomes. This may cause pregnancy loss or defects in the child.

Trisomy 21 or Down Syndrome is a disease caused by the extra copy of chromosome 21. It causes changes in facial appearances and developmental delays. Besides the 21st chromosome, other chromosomal defects are trisomy 18 (Edwards Syndrome), trisomy 13(Patau syndrome), trisomy 45(Turner’s Syndrome) and 47, XXY (Klinefelter syndrome).

Conclusion

The females have only X chromosomes and males have X and Y chromosomes hence, the sex of the baby is determined by the males. The new cell or this formed zygote will have 23 pairs or 46 chromosomes.