Question

How does sex determination take place in human beings?

Answer 1

Hint: In humans, each cell contains 23 pairs of chromosomes in that 22 pairs are autosomes and one pair sex chromosome. The sex chromosome participates in sex determination and they differ from autosomes in the form, size, and behavior.

Complete answer:
Sexual differences in humans are starts with the XY sex-determination system. It is a complex mechanism which is responsible for the development of the phenotypic differences between male and female from an undifferentiated zygote. Male human consists of one X chromosome and one Y chromosome, known as heterogametic. However, females have two copies of X chromosomes and known as homogametic. In humans, biological sex is mainly determined by five factors present at birth:
The presence or absence of a Y chromosome: The Y chromosome triggers male development while the absence of a Y chromosome leads to female development. Due to the presence of the sex-determining region in the Y chromosome, it is also known as the SRY gene.
The type of gonads: Primary sex determination involves the determination of gonads. The male gonads are the testicles that produce sperm in the form of spermatozoa. However, the female gonads are the ovary which produces egg cells.
The sex hormones: Male sex hormone is testosterone which is mainly responsible for sexual behavior in males. While female sex hormones include estrogens and progesterone.
The internal genitalia: The female internal genital organs involved ovaries, fallopian tubes, uterus, cervix, and vagina. While the male internal genital organs are testes, epididymis, and vas deferens.
The external genitalia: The external genitalia organs in males are the penis and scrotum and the female external genital organs include the labia minora, majora, and clitoris.

Note: -XO sex-determination system is a variant of the XY system which is observed in grasshoppers, crickets, and cockroaches. In this system, females have two similar chromosomes (XX) while males have only one chromosome (XO). Here, sex is determined by the number of genes expressed across the two chromosomes.
-ZW sex-determination system is reversed to the XY- system and it is found in birds, some reptiles, and some insects. In ZW- system females have two different types of chromosomes (ZW) and males have two similar chromosomes (ZZ).