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  Biology (NTSE/Olympiad)  

7. Heredity & Evolution

Sex Determination

Sex Determination
It is a process by which the sex of a person is determined. Genetics is involved in the determination of the sex of a person, which is explained as follows :
A male has one X chromosome and one Y chromosome, i.e., half of the male gamete or sperms will have X chromosome and the other half will have Y chromosome.
A female has two X chromosomes, i.e., all the female gametes or ova will have only X chromosomes.
Sex of a child depends on what happens at fertilisation.
If a sperm carrying X chromosome fertilises an ovum which carries X chromosome, then the child born will be a girl.
If a sperm carrying Y chromosome fertilises an ovum which carries X chromosome, then the child born will be a boy.
Thus, the sperm determines the sex of the child.
Sex determination is also controlled by the environmental factors in some animals.
For example, in some reptiles like turtle, high incubation temperature leads to the development of female offsprings, while in case of lizard. high incubation temperature results in male offsprings.

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