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Question
Explain how the sex of the child is determined at the time of conception in human beings.
Solution
Every somatic (body) cell of humans contains 23 pairs of chromosomes. Out of these 23 pairs, the first 22 pairs (44 chromosomes) do not determine the sex of an individual and they are known as autosomes. The remaining one pair determines the sex of the individual. This last pair is known as the sex chromosomes and are represented as X and Y.
The male gametes have 22 autosomes and either an X or a Y sex chromosome.
On the other hand, the females have XX sex chromosomes, along with the 22 autosomes. This means that their gametes can only have an X sex chromosome
Therefore, the sex of the child is determined by the type of the sperm (containing an X or a Y sex chromosome) which fuses with the egg cell (containing an X chromosome) at the time of conception.
If the X gamete of the male fuses with the X gamete of the female, then the offspring will be female.
On the other hand, if the Y gamete of the male fuses with the X gamete of the female, then the offspring will be male.
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