Question

With regard to the ABO blood types in humans, determine the genotype of the male parent and female parent shown here:
Male parent: Blood type B; mother type O
Female parent: Blood type A; father type B
Predict the blood types of the offspring that this couple may have and the expected proportion of each.

Accepted Answer

Step 1: Determine the possible genotypes of the male parent. Since the male has blood type B and his mother has blood type O, the male must have inherited an O allele from his mother. Therefore, the male's genotype is heterozygous B\/O ($$ I^B I^O ). $$Step 2: Determine the possible genotypes of the female parent. The female has blood type A and her father has blood type B. Since the father is type B, he could have passed either a B or an O allele. The female's genotype could be either A\/A ($$ I^A I^A ) or A$$\/O ($$ I^A I^O ). $$Both are possible, so consider both cases for offspring prediction. Step 3: Set up Punnett squares for each possible female genotype crossed with the male genotype B\/O ($$ I^B I^O ). $$For the female genotype A\/A ($$ I^A I^A $$), cross $$ I^A I^A $$ with $$ I^B I^O . $$For the female genotype A\/O ($$ I^A I^O $$), cross $$ I^A I^O $$ with $$ I^B I^O . $$Step 4: From each Punnett square, list all possible genotypes of the offspring and determine their corresponding blood types: A ($$ I^A I^A  or$$ $$ I^A I^O $$), B ($$ I^B I^B  or$$ $$ I^B I^O $$), AB ($$ I^A I^B $$), and O ($$ I^O I^O ). $$Step 5: Calculate the expected proportion of each blood type among the offspring by counting the frequency of each genotype in the Punnett square and converting it to a percentage or fraction.

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Key Concepts

ABO Blood Group System

Genotype Determination from Phenotype and Parental Information

Punnett Square and Probability of Offspring Genotypes