Kaplan Nursing Entrance Exam Practice 2026 – Comprehensive Prep

To determine the expected ratio of black to white offspring when crossing two black mice, it's important to first understand the genetics involved. Assuming that coat color in mice follows simple Mendelian inheritance, the black color could be represented by a dominant allele (B), while white could be represented by a recessive allele (b).

If both the male and female black mice are homozygous (BB), all offspring will be black. If they are heterozygous (Bb), a Punnett square can be used to predict the offspring's genotypes. In this case, crossing two Bb mice would produce a 3:1 ratio of black (BB and Bb) to white (bb) offspring, resulting in a final ratio of 75% black to 25% white, or a 3:1 ratio.

If both parents are homozygous black (BB), there would be no white offspring produced. The calculation of offspring ratios is dependent on the allele combinations of the parents. In this scenario, neither a 3:2 nor a 3:5 ratio would accurately represent the relationship based on simple Mendelian genetics, as these ratios do not fit the expected outcomes from the Punnett square analysis commonly used for monohybrid crosses.