Sex Determination in Humans
Genetic inheritance is the process by which sex of human beings is determined. Genes inherited from the parents to identify the sex of the offspring whether it will be a boy or a girl.
All the genes that contains all the characters for a offspring, are linearly arranged on chromosomes. Genes for sexual characters also include in these chromosomes.
Usually, all the characters related to the reproductive system are known as sexual characters and those that are not related to are the reproductive system known as vegetative characters. Sex chromosomes, that carry genes for sexual characters and those that chromosomes carry genes for the vegetative characters are known as autonomies.
Y chromosome is the sex chromosome that carries the genes for male characters and the X chromosome that carries the genes for female characters.
We have a total number of 46 chromosomes. Half of these 46 chromosome come from the mother and the rest, from the father. 44 are autonomies and 2 are sex chromosomes out of these 46 chromosomes. The sex chromosomes are not always in a perfect pair. there are 44 autonomies and two X chromosomes In females , and there are 44 autonomies, one X chromosomei n males and one Y chromosomes. In female, there are 44 + XX, and other hand the chromosomes in man are 44 + XY.
In the process of gamete formation, the normal diploid chromosome number is halved. This is known as haploid condition. All eggs of a female have 22 + X chromosomes. A male produces two types of sperms—one type carries the 22 + X composition and the other 22 + Y chromosomes. So, in every 100 sperms, 50 have Y chromosomes and 50 have X chromosomes.
X or Y any one of this can fertilize the egg. If a Y sperm fertilizes the egg, then the zygote has the 44 + XY composition, and the result of it, the embryo develops into a boy. When a X sperm fertilizes the egg, and the result of it, the zygote has the 44 + XX composition, this embryo grows into a girl. From the mother all the children inherit one X chromosome.
So, the sex is always determined by the sex chromosome of the father. If one who inherits the Y chromosome of the father is a boy and if one who inherits the X chromosome of the father is a girl.