Usually, one allele is called dominant, which means that an organism will always have that trait if the dominant allele is present. The other allele is called recessive, which means that its effects are masked when the dominant allele is present. Which allele do you think is dominant in the mice? Which allele is recessive? Explain your reasoning.

Explanation:

Since there is no extra information about a specific gene and its inheritance patterns, I am going to base my answers of examples I create.

To begin with, in a pair of alleles, dominant alllele is represented by A (Capital letter) and recessive is done by a (small letter). If an organism has AA (homozygous dominant) it will always show the dominant trait. If it has Aa (heterogyzous dominant) it will also show the dominant trait as one of the alleles is dominant, and finally if it as aa then it will show recessive trait

Which allele in mouse is dominant vs recessive is primarily figured out based on inheritance pattern. If majority of offspring represent a certain trait like black fur coat it is likely that the dominant trait for that gene is black fur coat. Allele that is recessive is masked by the dominant allele so if parents are

Aa * Aa ---> you'll get 4 genotypes AA, Aa, Aa,aa (Here the AA, Aa, Aa will all show the dominant trait because the capital letter A represents dominant allele and it masks the small letter a) whereas, aa will show recessive trait because there is no capital letter or dominant allele to mask the recessive trait.