Question

How is sex determined of an unborn baby?

Answer 1

Sex-determination is a biological system that determines the development of sexual characteristics in an organism. In simple words sex determination is nothing but to know whether the unborn baby is boy or a girl.

Complete answer:
An attempt to determine foetal sex should not be made before 12 weeks of gestation because it is relatively inaccurate at this early stage. After 13 weeks, 99 to 100 percent of cases without malformed external genitalia are accurate.

Sonographic foetal sex determination at the end of the second trimester is based on direct visualisation of the external genitalia, whereas at the end of the first and early second trimester, it is mainly based on the direction of the genital tuber in the direction of the genital tuber in the direction of the female foetus and the upward direction of the male foetus.

All humans have 46 chromosomes with 23 pairs of chromosomes. Two of these chromosomes, X & Y, are sex chromosomes. A female has two X and a male has one X and one Y chromosomes. Female gamete ovum and male gamete sperm have only one set of chromosomes. The unfertilized egg has always one X chromosome, but the sperm can have two different types of chromosomes.

They could have either an X chromosome or a Y chromosome. When the male X chromosome sperm fertilises the egg (X chromosome), the zygote would have two X chromosomes and develop into a female child. But if the sperm contains the Y chromosome and fertilises the egg (X chromosome), the zygote would develop into a male child (XY). It is therefore clear that the sex of the unborn child is determined by the father's sex chromosome.

The Y chromosome carries a critical gene called SRY, which acts on another gene called SOX9 to initiate the development of the embryo testes. High levels of the SOX9 gene are needed for the normal development of the testis. However, if there is some disruption to SOX9 activity and only low levels are present, the testis will not develop, resulting in a child with a sexual developmental disorder.

Note: 90% of human DNA is made up of so-called 'junk DNA or dark matter,' which does not contain genes but carries important regulators that increase or decrease gene activity. These regulatory segments of DNA are referred to as enhancers. If these enhancers that control testis genes are disrupted, it may lead to the birth of a child with a sexual development disorder.