Sex Determination - Boy Or Girl

What is Sex Determination?

A sex-determination is the biological system that determines the development of sexualcharacteristics in an organism. There are two different types of sexes – male and female.Chromosome play an important role in determining the sex of an individual.

Let’s have a glimpse into sex determination and who determine the gender of the baby- father or mother.

Comparatively, sexual reproduction is much more complex than asexual reproduction. Sexual reproduction is a slow and lengthy process. The process begins with gamete formation in the male and female body. Through sexual intercourse, these male and female gametes meet and fuse to form a unicellular zygote. It continues with multiple divisions of the zygote to form a multicellular embryo which eventually develops into a complete fetus. The complete process take 9 months to deliver this baby.

Sex Determination

Sex Determination: Boy/ Girl

What is Fertilization?

Fertilization is the process in which two gametes (sex cells) – sperm and ova – fuse together to form a new cell called zygote. During this unbiased event, all genetic information from parents to the child has been transferred. Also, the gender of the child is determined and the father of the child is responsible for the sex determination.

What are Chromosomes?

Chromosomes are a thread like structure holding genetic information. It is present in the cell nuclei. A normal cell contains 23 pairs (46n) of chromosomes. Out of these, one pair (2n) is sex chromosomes. Sex chromosomes are denoted as X and Y. A male cell contains XY sex chromosomes while a female cell contains XX sex chromosomes.

A gamete contains only 23 chromosomes (23n). A sperm contains either an X or Y chromosome i.e. there will be two sets of sperms. One set of sperm consists of only X chromosomes while another set consists of only Y chromosomes. An ovum always contains an X chromosome. Sex of the child depends on the kind of sperm that fuses with the ovum.

During sexual intercourse, the father ejects both types of sperms i.e X chromosome and Y chromosome sperms.

  1. If the sperm with X chromosome fertilizes the ovum of X chromosome, the zygote would have XX chromosomes and the child will be a girl.
  2. If the sperm with Y chromosome fertilizes the ovum of X chromosome then the zygote would have XY chromosomes and the child will be a boy.
Sex Determination

Sex determination

To learn more about sex determination with the interactive video lessons, visit BYJU’S.


Practise This Question

Sex chromosomes in a boy are identical.