Kaplan Nursing Entrance Practice Exam

What must be true about male mouse II after crossing with the same female that produced albino offspring?

1. Male mouse II is homozygous

2. Male mouse II is heterozygous

3. Male mouse II is albino

4. Male mouse II is recessive

The correct answer is: Male mouse II is heterozygous

In the context of genetics, crossing a male mouse with a female mouse that produced albino offspring can provide insight into the genotype of the male mouse. The key fact to understand is that albino in mice is typically a recessive trait. This means that to express the albino phenotype, an individual must have two copies of the recessive allele. If the female produced albino offspring, it must have at least one recessive allele for the albino trait. If male mouse II is also producing albino offspring with this female, he cannot be homozygous dominant, as that would not allow for any recessive traits (like albino) to appear in the offspring. For albino offspring to occur when crossing with a female that produces them, male mouse II must carry at least one recessive allele. Therefore, he must be heterozygous, meaning he has one dominant allele (which could express a different phenotype) and one recessive allele, allowing the possibility of albino offspring when combined with the female's genetic contribution. Thus, we arrive at the conclusion that male mouse II is heterozygous, which accounts for the presence of these albino offspring when he is crossed with a female mouse that can provide the necessary recess