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Science · 2026 · 3 marks
CBSE 2026 · Region 1 · Set 2 · Q13
(a)A couple are parents to $\displaystyle 4$ daughters in a sequence, and do not have any son. Does this indicate that the husband does not produced Y-chromosome bearing sperms ? Explain.(b)What are the chances of this couple bearing yet another daughter ? Show with the help of a cross.
(a)
A couple are parents to $\displaystyle 4$ daughters in a sequence, and do not have any son. Does this indicate that the husband does not produced Y-chromosome bearing sperms ? Explain.
(b)
What are the chances of this couple bearing yet another daughter ? Show with the help of a cross.
Marking-scheme solution
(a) No, it is purely a matter of chance, as male produces $\displaystyle 50$% X-type and \(\displaystyle 50 \%\) Y-type of sperms and any sperm can fertilize the ova.
$\displaystyle 50$% chance.
Parents : XX x XY Mother
$\displaystyle 2$ girls : $\displaystyle 2$ boys $\displaystyle 50$% chance of daughter.CBSE Class 10 Science past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.