Unlocking the Secrets of Genetics in Crossbreeding Mice

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

• A. Male mouse II is homozygous
• B. Male mouse II is heterozygous
• C. Male mouse II is albino
• D. Male mouse II is recessive

Answer: (B)

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

When it comes to genetics, a fascinating game of chance and heritage unfolds, especially in tiny creatures like mice. If you’ve ever wondered about the complexities of inheritance—particularly when it comes to breeding albino mice—you’re in for a treat. Let’s break it down in simpler terms, imagining ourselves in the shoes (or paws) of the mice involved.

Picture this: you have a female mouse that proudly gives birth to several adorable albino offspring. Now, what does that say about her own genetic makeup and that of her mate, whom we’ll refer to as male mouse II? Here’s the key fact to chew on: albino mice owe their snowy-white coats to a recessive trait, meaning that they only show up if the mouse carries two copies of the recessive allele.

Now, for male mouse II, the situation becomes intriguing. He can’t be homozygous dominant, which means he can't just carry dominant alleles. If that were the case, the offspring wouldn't include any albinos. So, what about the males in this mix? If male mouse II produces albino offspring with the female, he must carry at least one recessive allele himself. Voilà! This leads us to the conclusion that male mouse II is heterozygous—a genetic cocktail of one dominant allele and one recessive allele.

Let’s think of it this way. Imagine you’re at a diner, staring at a menu stuffed with rich options. You only know you want pie, but you’re not sure if you prefer apple or cherry. By choosing a slice of apple, you've admitted you enjoy both flavors. Similarly, male mouse II has a dominant allele that might express another trait, but he's also holding on to the potential for that recessive albino trait, waiting to shine through in the offspring.

Now, why does this matter? Well, understanding these genetic underpinnings can enlighten us not just about mice but about biology as a whole. Every time we pair two organisms, we’re playing a complex game of roulette, and understanding whether one is heterozygous or homozygous helps predict what traits offspring might inherit.

So, as we pull back and reflect on this genetic journey, think about how male mouse II’s heterozygosity influences the next generation and possibly your classroom assignments, or even your conversations about genetics in casual settings. Whether in a lab class or a lively dinner discussion, that knowledge can spark more inquiries.

In summary, with the female mouse producing albino offspring, you can bet on the fact that male mouse II supports this phenomenon with his heterozygous nature. And next time you crossbreed your own little lab mice, you'll know exactly what to look for!