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Science · 2025 · 3 marks
CBSE 2025 · Region 1 · Set 3 · Q30
(a) How many chromosomes are present in human beings? Out of these how many are sex chromosomes? (b) Explain how, in sexually reproducing organisms,…
(a)
How many chromosomes are present in human beings ? Out of these how many are sex chromosomes?
(b)
Explain how, in sexually reproducing organisms, the number of chromosomes in the progeny is maintained.
Marking-scheme solution
$\displaystyle 23$ pairs or $\displaystyle 46$ chromosomes
$\displaystyle 1$ Pair or $\displaystyle 2$ chromosomes
(b) In sexually reproducing organisms chromosomes occur in pairs. The members of the pair separate at the time of gamete formation. The two germ cells fuse and form zygote thus restore the same number of chromosomes as their parents.
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CBSE Class 10 Science past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.