Understanding the Inheritance of Fur Color in Rats

The Mendelian Genetics of Fur Color Inheritance

Inheritance of fur color in rats follows the principles of Mendelian genetics. This means that certain traits, such as fur color, are determined by specific genes that follow predictable patterns of inheritance.

Dominance of Black Fur Color

Black fur color is dominant over white fur color in rats. This means that if a rat carries at least one allele for black fur color (B), it will exhibit black fur, as the black fur allele masks the expression of the white fur allele (b).

Genetic Cross Analysis

In the scenario described, a heterozygous rat (Bb) is crossed with a rat that has white fur (bb). The heterozygous rat carries one allele for black fur color and one allele for white fur color, while the other rat carries two alleles for white fur color.

Expected Genotypic Ratio

When these two rats are crossed, the expected genotypic ratio among the offspring would be 50% Bb (black fur) and 50% bb (white fur).

Phenotypic Expression

However, since the dominant black fur allele (B) is expressed over the recessive white fur allele (b), the expected phenotypic ratio among the progeny would be 100% black fur.

Conclusion

In conclusion, the expected ratio of fur color among the progeny when crossing a heterozygous rat with a rat with white fur is 100% black fur, due to the dominance of the black fur allele in inheritance.