Question

In a dihybrid cross, $F2$ ratio of $15:1$ is due to
A. Supplementary genes
B. Dominant epistasis
C. Duplicate genes
D. Recessive epistasis

Answer 1

As we know that, in a dihybrid cross- we can determine whether the individual is homozygous or heterozygous dominant. In a test cross, an individual breed with another individual that is homozygous for the recessive trait and offspring of the test cross is determined. This test has two possibilities- if any offspring produced express the recessive trait, the individual is heterozygous for the dominant allele. If all the offspring produced express the dominant trait, the individual is homozygous for the dominant allele.

Complete answer:
Option A Supplementary genes- supplementary genes are known to have a single characteristic gene where one gene can suppress or mask the effect of other genes. Supplementary genes are termed to be one gene producing a characteristic and another gene is supplement to it.
Option A is not correct.
Option B Dominant epistasis- the ratio of dominant epistasis is $12:3:1$. When one locus' dominant allele causes a certain phenotype regardless of the allelic status of the other locus. It is said that the dominant allele of one gene masks the effect of the other gene which is recessive.
Option B is not correct.
Option C Duplicate genes- gene duplication or duplicate gene interaction is provided when colour is recessive to no colour at one allelic pair. So, in a dihybrid cross, $F2$ ratio of $15:1$ is due to the duplication of genes.
Option C is correct.
Option D Recessive epistasis- recessive epistasis is when recessive allele of one gene masks the effect of allele of the second gene. Examples of epistasis are pigmentation in mice.
Option D is not correct.

Hence, Option C is the correct answer.

Note:
As we know that Each organism carries two copies of each trait- one was a dominant trait and one is recessive. Dihybrid cross referred to involvement of two sets of allelic pairs. Dihybrid examples can be a test cross. As we know that, dwarf, tall, pink all are Characteristics of phenotype or morphological characters. The test cross is an experiment showcased by Gregor Mendel, in his studies of the genetics of pea plant.