Understanding the ABO Blood Group Inheritance in Humans

1. In humans, if an AO person mates with an OO person, what are the possible genotypes and phenotypes of the children and the percentage of each phenotype?

1. **Possible genotypes:** AO (50%), OO (50%); **Phenotypes:** Blood types A (50%), O (50%).

Explanation:

In this scenario, when an AO person mates with an OO person, their children can inherit either an A allele from the AO parent or an O allele from the OO parent. This results in two possible genotypes: AO (50%) and OO (50%). The corresponding phenotypes are blood type A (50%) for the AO genotype and blood type O (50%) for the OO genotype. This demonstrates the Mendelian inheritance of the ABO blood group system, where the A allele is dominant over the O allele, leading to varying blood types based on the combination of inherited alleles.

2. In humans, if two people who are blood type B and both carry an O gene mate, what are the possible genotypes and phenotypes of their children and the percentage of each?

2. **Possible genotypes:** BO (50%), OO (50%); **Phenotypes:** Blood types B (50%), O (50%).

Explanation:

In the case of two individuals with blood type B who both carry an O gene, their children's genotypes can arise from the combination of these alleles. This results in two possible genotypes: BO (50%) and OO (50%). The phenotypes corresponding to these genotypes are blood type B (50%) for the BO genotype and blood type O (50%) for the OO genotype. The presence of the recessive O allele prevents the production of antigens on the blood cells, contributing to the expression of the O blood type.

3. In humans, if a person with the genotype AA mates with a person with the genotype OO, what are the possible genotypes and phenotypes of their children and the percentage of each?

3. **Possible genotype:** AO (100%); **Phenotype:** Blood type A.

Explanation:

When a person with genotype AA, carrying two dominant A alleles, mates with an individual with the genotype OO, carrying two recessive O alleles, their offspring will inherit one A allele from the first parent and one O allele from the second parent. This leads to a 100% occurrence of the AO genotype in the children, resulting in blood type A (phenotype). The dominant A allele dictates the expression of the A blood type, while the O allele remains inactive in this context.

4. In humans, if a person with the genotype AO mates with a person with the genotype AO, what are the possible genotypes and phenotypes of their children and the percentage of each?

4. **Possible genotypes:** AO (25%), AA (25%), OO (50%); **Phenotypes:** Blood types A (25%), AB (25%), O (50%).

Explanation:

When individuals with AO genotypes mate, their children's genotypes are determined by the combination of alleles. The possible genotypes are AO (25%), AA (25%), and OO (50%). The corresponding phenotypes are blood type A (25%), blood type AB (25%), and blood type O (50%). Blood type AB, which has both A and B antigens, can only occur if one parent contributes the A allele (AA) and the other contributes the B allele (BO).

5. In humans, if a person who is type A mates with a person who is type B and they have one child who is type O, what are the parents' genotypes, and what are the possible genotypes and phenotypes of their children and the percentage of each?

5. **Parents' genotypes:** AO, BO; **Possible genotypes:** AO (50%), BO (50%); **Phenotypes:** Blood types A (50%), B (50%).

Explanation:

If a person with blood type A (genotype AO) mates with a person with blood type B (genotype BO), and they have a child with blood type O, the genotypes of the parents must be AO and BO. This results in two possible genotypes for their children: AO (50%) and BO (50%), which correspond to blood types A (50%) and B (50%). The Punnett square illustrates the inheritance patterns, where the child's type O blood arises from inheriting an O allele from each parent. Understanding the ABO blood group system and its genetic basis provides insights into how specific alleles contribute to the diversity of blood types in humans.
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