Two brothers, one has blood group A, while the other has blood group O. What can be concluded about their parents?

B. One parent (at least) must be heterozygous

A. Both parents must be homozygous

B. One parent (at least) must be heterozygous

C. Both parents must have blood group O

D. Both parents must have blood group A

Everyday Science · Circulatory System (Human Biology) · page 4 of 4

Blood Groups MCQs with Answers

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31.
Two brothers, one has blood group A, while the other has blood group O. What can be concluded about their parents?
Correct Answer: B. One parent (at least) must be heterozygous
One-liner
At least one parent must be heterozygous, because a child with blood group O (genotype OO) requires an O allele from each parent, while the other child's group A can come from a heterozygous parent (AO).
32.
The gene for blood group is present on which chromosome number?
Correct Answer: B. Chromosome 9
One-liner
The gene for blood group (ABO system) is present on chromosome 9.