The figure shows the human reproductive cycle of sex determination.  Whether a baby is a boy or a girl is determined by:
AWhether the baby is the first child or not
BThe mother's nutrition during pregnancy
CThe kind of sex chromosome carried by the SPERM that fertilises the egg — X gives a girl, Y gives a boy
DThe age of the parents at conception
Answer & Solution
Correct answer: C. The kind of sex chromosome carried by the SPERM that fertilises the egg — X gives a girl, Y gives a boy
All eggs carry an X chromosome. Sperms carry either X or Y. An X-bearing sperm + X-bearing egg → XX → female. A Y-bearing sperm + X-bearing egg → XY → male. So the sex of the baby is decided by which sperm fertilises the egg — that is, by the father. Blaming the mother for the child's sex is biologically wrong.
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