Q.How is sex determined in human beings?
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Start your 14-day free trial to unlock the full solution →Step 1. State the human chromosome set: of the 23 pairs, 22 are autosomes (44A) and one pair is the sex chromosomes — XX in a normal female, XY in a normal male.
Step 2. State each parent's gamete output: the homogametic mother produces only one type of egg, always carrying a single X chromosome (22A+X); the heterogametic father produces two types of sperm in roughly equal numbers, one carrying an X chromosome (22A+X) and one carrying a Y chromosome (22A+Y).
Step 3. Combine at fertilisation: an egg (always X) fertilised by an X-bearing sperm gives a 44A+XX zygote, developing as female; an egg fertilised by a Y-bearing sperm gives a 44A+XY zygote, developing as male. Because the egg's contribution is fixed, it is entirely the father's sperm type that decides the outcome. …
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