Directions: Watch this video and then use the information below to answer any questions that follow.

Question

There are three different alleles for blood-type: A, B, and O. A and B are dominant over O. If a person has A and B genes, he or she has blood-type AB. This is referred to as a codominant pattern of heredity.

Jane's mother and father have type B blood. When Jane's blood was tested, she found she had a blood-type of O. Select the best response from the options below.

Modes of Inheritance | BioNinja



a
One of them has a recessive gene for type O blood.
b
Both parents are homozygous for type B blood.
c
One of them is homozygous for type B blood.
d
Both parents have a recessive gene for type O blood.

Answer 1

To determine the best response from the provided options, we need to consider the inheritance of the blood type alleles.

Jane's parents both have type B blood. The possible genotypes for type B blood are:

1. Homozygous (BB) - two dominant alleles
2. Heterozygous (BO) - one dominant allele (B) and one recessive allele (O)

Since Jane has type O blood, her genotype must be OO (recessive). This means she must have inherited one O allele from each parent. Therefore, for Jane's parents to have a child with type O blood, at least one of them must carry the recessive O allele.

Now, let's analyze the options:

a) One of them has a recessive gene for type O blood.

• This could be true if one parent is heterozygous (BO).

b) Both parents are homozygous for type B blood.

• This cannot be true, as two BB parents cannot produce an OO child.

c) One of them is homozygous for type B blood.

• This could be true if the other parent is heterozygous (BO). However, it does not ensure Jane could have type O blood as both homozygous B (BB) parent wouldn't pass on an O allele.

d) Both parents have a recessive gene for type O blood.

• This implies both are BO. This is true since both can pass an O allele to create a child with type O blood.

Based on this reasoning, the best response is:

a) One of them has a recessive gene for type O blood.

This refers to the scenario where one parent is heterozygous (BO), allowing for the production of a child with OO (type O blood).