CBSE 2025 · Region 5 · Set 2 · Q23 · 3 marks
Study the diagram above and answer the following questions :(a)How many alleles are involved in blood grouping?(b)A person having 'AB' blood group has both dominant alleles. What is this inheritance type called ?(c)A man with 'A' blood group marries a woman with 'B' blood group. Can they have a child with 'O' blood group? Explain with the help of a cross.
Study the diagram above and answer the following questions :
(a)
How many alleles are involved in blood grouping?
(b)
A person having 'AB' blood group has both dominant alleles. What is this inheritance type called ?
(c)
A man with 'A' blood group marries a woman with 'B' blood group. Can they have a child with 'O' blood group? Explain with the help of a cross.
Marking-scheme solution
(a)
Three alleles
(b)
Co-dominance.
(c)
Yes, they can have a child with ‘O’ blood group
Cross: Father (A, $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{i}$) x Mother (B, $\displaystyle \mathrm{I}^{\mathrm{B}} \mathrm{i}$) -> gametes $\displaystyle \mathrm{I}^{\mathrm{A}}$, $\displaystyle \mathrm{i}$, $\displaystyle \mathrm{I}^{\mathrm{B}}$, $\displaystyle \mathrm{i}$ -> children $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{B}}$ (AB), $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{i}$ (A), $\displaystyle \mathrm{I}^{\mathrm{B}} \mathrm{i}$ (B), $\displaystyle \mathrm{i} \mathrm{i}$ (O).
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CBSE Class 12 Biology past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.