CBSE 2024 · Region 4 · Set 1 · Q23 · 3 marks
(a)A man with blood group 'A' marries a woman with blood group 'AB'. The first child born to them has blood group 'B'. Work out a cross to find the genotype of the father. Give the possible blood groups and their genotypes of the children that could be born to this couple. (Use a Punnet square).(b)State the basis of 'ABO' blood grouping in humans.
(a)
A man with blood group 'A' marries a woman with blood group 'AB'. The first child born to them has blood group 'B'. Work out a cross to find the genotype of the father. Give the possible blood groups and their genotypes of the children that could be born to this couple. (Use a Punnet square).
(b)
State the basis of 'ABO' blood grouping in humans.
Marking-scheme solution
(a)
Father genotype - $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{i}$
Parents- $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{i}$ X $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{B}}$
Possible genotype- $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{A}}$ , $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{i}$, $\displaystyle \mathrm{I}^{\mathrm{B}} \mathrm{i}$, $\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{B}}$,
Possible blood group- A, AB, B
(b)
It is controlled by gene ‘I’ having $\displaystyle 3$ alleles ($\displaystyle \mathrm{I}^{\mathrm{A}} \mathrm{I}^{\mathrm{B}} \mathrm{i}$) , The blood group is determined by the type of sugar polymer present on the plasma membrane of the RBC.
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CBSE Class 12 Biology past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.