In a couple having three daughters, the mother is sometimes wrongly blamed for the sex of the children. The scientific reason this blame is COMPLETELY UNJUSTIFIED is:
AHormones from the mother decide the sex after birth
BSex is decided by the food the mother eats
CThe mother does not contribute any chromosomes
DThe mother always contributes only an X chromosome; the sex of the baby depends on whether the sperm (from the father) carries an X or a Y chromosome
Answer & Solution
Correct answer: D. The mother always contributes only an X chromosome; the sex of the baby depends on whether the sperm (from the father) carries an X or a Y chromosome
Every egg cell from the mother carries an X chromosome — she has nothing else to give. Sperm cells from the father come in two types: X-bearing and Y-bearing. The X-or-Y sperm that fertilises the egg therefore decides whether the child is XX (female) or XY (male). So sex determination is genetically the father's contribution, not the mother's.
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