The gene for white fur in the fox is dominant. The recessive gene (a) corresponds to the black color.

The gene for white fur in the fox is dominant. The recessive gene (a) corresponds to the black color. Foxes can be blind due to the influence of the recessive gene (b). The white female from the black male gave birth to 50% of white, 25% of blind and 75% of sighted cubs. Analyze the parental organisms by phenotype and genotype and make a crossing scheme.

Since in the offspring of these foxes there are blind (bb) and black (aa) cubs with genotypes homozygous for genes for recessive traits, and they inherit recessive genes from both parents, it should be concluded that the white female is heterozygous in color, as well as the presence of a gene for blindness in both parents.

By sight, the cleavage corresponds to a ratio of 3: 1, which characterizes the crossing of two heterozygotes. Taking into account this assumption, let us designate the genotypes of the parents as follows:

female – AaBb, has normal vision and white fur, produces four types of eggs – ab, AB, aB, Ab;

male – aaBb, has black fur and normal vision, produces two types of spermatozoa – aB and ab.

The offspring are represented by the following possible options:

sighted cubs with black fur (2aaBb, aaBB) – 37.5%;

sighted cubs with white fur (AaBB, 2AaBb) – 37.5%;

black blind cubs (aabb) – 12.5%;

blind cubs with white fur (Aabb) – 12.5%.

The obtained percentages coincide with those indicated in the problem statement, which confirms the assumption made.