Sex Determination in Humans (XX-XY type) ||Class 12 Biology

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     In humans, 23 pairs of chromosomes are present out of which 22 pairs are exactly same in both males and females, these are autosomes. The 23rd pair of chromosome is called sex chromosome. 
     A pair of X-chromosome (XX) is present in females, whereas one X and one Y chromosome (XY) is present in males. In males, during Spermatogenesis, two types of gametes are produced. 50% of the total sperm produced carry X chromosome and the rest 50% carry Y chromosomes besides autosomes. The female produces only one type of ovum with an X-chromosome.
     In case, the ovum fertilises with a sperm carrying X-chromosome, the zygote develops into a female (XX) and if ovum is fertilised with sperm carrying Y-chromosome, zygote formed will be a male (XY). Thus, the genetic makeup of sperm which fertilises an ovum determines the sex of a child. So, women should not be blamed for the sex of a child. There are total 50% chances of having a male child and 50% chances of having female child in each pregnancy.





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