Question

Genetics Problem: Mom is homozygous for type A blood, and Dad is heterozygous for type B blood. What is the percent chance that a child will have type AB blood? Type A? Type B? Type O? (pp. 483,485 )

Short answer

Answer: The probabilities for each blood type in their children are as follows: Type AB: 50%, Type A: 50%, Type B: 0%, and Type O: 0%.

Step-by-step solution

Understand the parental genotypes

To do this, we must first identify the blood type alleles of each parent. Since the mother has homozygous Type A blood, her genotype is AA. The father has heterozygous Type B blood, so his genotype is BO.

Set up the Punnett square

Next, create a Punnett square to determine the possible genotype combinations for their offspring. Label the rows with the mother's alleles (A and A) and the columns with the father's alleles (B and O).

Fill in the Punnett square

Fill in each cell of the Punnett square with the combination of the parental alleles from the corresponding row and column. The resulting Punnett square will be: B | O ------- A | AB | AO A | AB | AO

Determine genotype probabilities

Count the occurrences of each genotype in the table and divide that by the total number of genotypes, which is 4, to find the probability: AB: 2/4 = 1/2 or 50% AO: 2/4 = 1/2 or 50% All other combinations (BO, OO) do not appear, so their probabilities are 0.

Calculate blood type probabilities

Since AO and AA both result in Type A blood, combine their probabilities: Type A: AO (50%) --> 50% (All offspring with AO or AA) Type AB: 50% (All offspring with AB) Type B: 0% (No offspring with BB or BO) Type O: 0% (No offspring with OO) Now we have the probability distribution for the offspring blood types: Type AB: 50% Type A: 50% Type B: 0% Type O: 0%