A pair of laboratory mice are crossed to obtain offspring. Three alleles found in the female gamete are ABC Three alleles found in the male gamete are Abc. What most likely happened to the male gamete to get a unique combination of alleles? crossing over mutation tetrads fertilization

The most likely explanation for the unique combination of alleles in the male gamete is **crossing over**. <br /><br />Here's why:<br /><br />- **Crossing Over**: This process occurs during prophase I of meiosis when homologous chromosomes exchange segments of genetic material. This recombination results in new combinations of alleles on each chromosome, contributing to genetic diversity. Given that the male gamete has a unique combination of alleles (Abc), it is likely that crossing over occurred to produce this new combination.<br /><br />Let's briefly review the other options to understand why they are less likely:<br /><br />- **Mutation**: While mutations can introduce new genetic variations, they typically occur in the DNA sequence rather than during the formation of gametes. The question suggests a recombination event rather than a mutation in the DNA sequence.<br /><br />- **Tetrads**: Tetrads form during meiosis when homologous chromosomes pair up. However, tetrads themselves do not explain the creation of unique allele combinations; rather, they are a structure involved in the process of crossing over.<br /><br />- **Fertilization**: Fertilization involves the combination of male and female gametes to form a zygote. It does not explain the creation of unique combinations within a single gamete.<br /><br />Therefore, the most plausible explanation for the unique combination of alleles in the male gamete is **crossing over** during meiosis.