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(c) Sex determination in the unborn baby.
Sex of an unborn baby is determined when the egg cells of the women gets fertilized by the sperm cells of man and pregnancy takes place.
Sex chromosomes are present in the nuclei of each cell
- Male sperm has 2 sex chromosomes X and Y
- Female egg has 2 sex chromosomes X and X
When both fertilize,
X Chromosome of Male + X Chromosome of Female → XX Chromosome of Zygote ( Female )
Y Chromosome of Male + X Chromosome of Female → XY Chromosome of Zygote ( Male )
So sex of child is dependent upon father not mother(as fathers chromosome can be X or Y but mother is always X)