Q4 of 26 Page 284

Describe the sex determination in human beings

•In humans, the sex is determined by the genes located on chromosomes.

•Genes are inherited from parents to offspring.


•There are 23 pairs of chromosomes in humans. Out of 23 pairs, 22 pairs are autosomes which are similar in male and female.


•In female, the 23rd pair has two similar chromosomes called X-chromosome.


•In male, one chromosome in 23rd pair is X chromosome and the other is Y chromosome which is smaller in size.


•All eggs (ova) of female are similar. Each egg contains 22 autosomes and one X chromosome.


•Whereas in males, 50% sperms have X chromosome and 50% have the Y chromosome (along with 22 autosomes).


•If a sperm carrying X chromosome fertilizes an egg, the zygote develops into a female (XX along with autosomes).


•If a sperm carrying Y chromosome fertilizes an egg, the zygote develops into a male (XY along with autosomes).



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