Question

What are the phenotypes and genotypes for the ABO blood groups? If both parents are type AB blood, what are the possible genotypes and phenotypes for their children, including the expected percentages? (pages \(480-81\) )

Short answer

The ABO blood group system has 4 possible phenotypes (blood types): Type A, Type B, Type AB, and Type O. The possible genotypes are AA and AO for Type A, BB and BO for Type B, AB for Type AB, and OO for Type O. When both parents have Type AB blood, their children have a 25% chance of having Type A (genotype AA), a 25% chance of having Type B (genotype BB), and a 50% chance of having Type AB (genotype AB). Type O blood is not possible for their children.

Step-by-step solution

1. Understand the ABO blood group system

The ABO blood group system is determined by the ABO gene, which has three different alleles: A, B, and O. A person has two copies of the ABO gene, inheriting one allele from each parent. The A and B alleles are co-dominant, and the O allele is recessive. This means that if a person has both A and B alleles, both will be expressed (resulting in AB blood type).

2. Identify the possible alleles and blood types

There are 4 possible blood types (phenotypes) in the ABO blood group system: - Type A: Can have genotype AA or AO - Type B: Can have genotype BB or BO - Type AB: Has the genotype AB - Type O: Has the genotype OO

3. Use a Punnett square to determine the possible genotypes and phenotypes for the children

Since both parents have type AB blood, each parent has a genotype of AB. To determine the possible genotypes and phenotypes for their children, we can use a Punnett square. A Punnett square is a tool used to predict the possible outcomes of the offspring, based on the genotypes of the parents. Make a 2x2 grid and put the alleles of one parent along the top and the other parent's alleles along the side. ``` | A | B --------- A | AA | AB --------- B | AB | BB ```

4. Calculate the expected percentages for each genotype and phenotype

Based on the Punnett square, the possible genotypes and phenotypes along with their expected percentages for the children are as follows: - Genotype AA: 1 out of 4 or 25% - Genotype BB: 1 out of 4 or 25% - Genotype AB: 2 out of 4 or 50% In terms of phenotypes: - Type A (genotype AA or AO): 25% chance (only AA is possible in this case) - Type B (genotype BB or BO): 25% chance (only BB is possible in this case) - Type AB (genotype AB): 50% chance - Type O: 0% chance (since neither parent carries the O allele, it's impossible for their children to have type O blood) In conclusion, the possible genotypes for the children of type AB parents are AA, AB, and BB. The expected percentages are 25% for type A, 25% for type B, and 50% for type AB. Type O blood is not possible for their children.