PATHOLOGY MCQ
GENETICS AND DISEASE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Either the ‘A’ or ‘B’ phenotype in separate red blood cells
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The ‘B’ phenotype
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Both the ‘A’ and ‘B’ phenotype in each red blood cell
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The ‘A’ phenotype
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Detailed explanation-1: -In people with type AB blood, both A and B proteins are expressed on the surface of red blood cells equally. Therefore, this AB phenotype is not an intermediate of the two parental phenotypes, but rather is an entirely new phenotype that results from codominance of the A and B alleles.
Detailed explanation-2: -The A and B alleles are codominant. Therefore, if an A is inherited from one parent and a B from the other, the phenotype will be AB. Agglutination tests will show that these individuals have the characteristics of both type A and type B blood.
Detailed explanation-3: -Codominance. In people, one codominant trait that you can’t really observe by looking at a person, but many people know about themselves, is blood type. People with the AB blood type have one A allele and one B allele. Because both alleles are expressed at the same time, their blood type is AB.
Detailed explanation-4: -The ABO blood group antigens are encoded by one genetic locus, the ABO locus, which has three alternative (allelic) forms-A, B, and O. A child receives one of the three alleles from each parent, giving rise to six possible genotypes and four possible blood types (phenotypes).