Multiple Choice
In the context of variations of dominance, which statement best defines a dominant allele?
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3. Extensions to Mendelian Inheritance
Variations of Dominance
Multiple Choice
In the ABO blood group system (a variation of dominance known as codominance), what genotype would a person with type AB blood have?
A
B
C
D
Verified step by step guidance1
Understand that the ABO blood group system is controlled by a single gene with three alleles: \(I\^A\), \(I\^B\), and \(i\). The alleles \(I\^A\) and \(I\^B\) are codominant, meaning both are expressed equally when present together, while \(i\) is recessive.
Recall that blood type AB means that both A and B antigens are present on the surface of red blood cells, which occurs only if the genotype includes both \(I\^A\) and \(I\^B\) alleles.
Identify that the genotype for blood type AB must contain one \(I\^A\) allele and one \(I\^B\) allele, because codominance allows both alleles to be expressed simultaneously.
Recognize that genotypes like \(I\^A i\) or \(I\^B i\) correspond to blood types A and B respectively, and \(ii\) corresponds to blood type O, so these do not produce blood type AB.
Conclude that the genotype for a person with blood type AB is \(I\^A I\^B\), representing the codominant expression of both alleles.
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