Choose the correct answer from the four options given below:
In a human female, ovum consists of:
Topic: Chromosomes in the ovum
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Pick an option and check your answer. The full worked answer is below either way.
Answer
(d) 22 autosomes and 1 X-chromosome.
An OVUM is a GAMETE and therefore HAPLOID — it carries 23 single chromosomes, not 23 pairs. Those are 22 AUTOSOMES and 1 SEX chromosome.
The sex chromosome must be an X, because the mother is XX and every ovum receives one of her two X chromosomes. She has no Y to give, which eliminates option (c).
Options (a) and (b) both say PAIRS, which is the diploid number of a BODY cell — and this is the commonest error. Gametes are formed by MEIOSIS, which halves the number so that fusion at fertilisation restores the full 46.
THE POINT THAT FOLLOWS: since every ovum carries X, the sex of a child is determined entirely by whether the SPERM carries X or Y — that is, by the father.
22 autosomes and 1 X-chromosome.