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Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYPrinciples of Inheritance and Variation1 Mark
MCQ
In human beings, sex is determined:
  • A
    Before fertilization of ovum
  • B
    During 6th week of foetal life when androgens are produced
  • C
    At the time of fertilization of ovum
  • D
    During 7th and 8th weeks of foetal life when gonads differentiate into testis and ovary
✓

Answer

  1. At the time of fertilization of ovum

Explanation:

In humans, sex is determined by the father.

The mother produces only one kind of gamete - having X-chromosome only.

The father produces two kinds of gametes - where one contains the X chromosome and another one contains the Y chromosome.

During fertilization, if the X chromosome of the father fuses with the ovum of the mother, which contains an X chromosome, it becomes a girl child.If the Y chromosome of the father fuses with the ovum containing X in the mother, it results in a boy.

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