Question

Match the following genetic phenomena with their respective ratios.

Column I	Column II
A. Inhibitory gene ratio	\[1\]. \[9:3:4\]
B. Complementary gene ratio	\[2\]. \[1:1:1:1\]
C. Recessive epistasis ratio	\[3\]. \[12:3:1\]
D. Dihybrid test cross ratio	\[4\]. \[13:3\]
E. Dominant epistasis ratio	\[5\]. \[9:7\]

A. A-\[5\], B-\[4\], C-\[3\], D-\[2\], E-\[1\]
B. A-\[4\], B-\[5\], C-\[1\], D-\[2\], E-\[3\]
C. A-\[1\], B-\[2\], C-\[4\], D-\[3\], E-\[5\]
D. A-\[2\], B-\[1\], C-\[4\], D-\[5\], E-\[3\]
E. A-\[5\], B-\[4\], C-\[1\], D-\[2\], E-\[3\]

Answer 1

Hint: When \[2\] different genes which are not alleles, affect the same character in such a way that the expression of one mask or suppress the expression of the other gene. It is referred to as epistasis. The gene that suppresses is said to be epistatic and the gene which remains obscure is hypostatic.

Complete answer:
A. Inhibitory gene ratio: Inhibitory gene interaction is also known as Dominant (Inhibitory) epistasis. In this type of epistasis, a dominant allele at one locus can mask the expression of both the dominant and recessive alleles at the second locus. An example of such a gene interaction is found in anthocyanin pigmentation in rice. Inhibitory gene ratio is \[13:3\].
A. of column I matches correctly with option \[4\]. Of column II.
B. Complementary gene ratio: Complementary gene epistasis is also known as Duplicate recessive epistasis. In this type of epistasis, recessive alleles at either of the two loci mask the expression of dominant alleles at the two loci. The best example of this is found in flower colour in sweet pea. Complementary gene ratio is \[9:7\].
B. Of column I matches correctly with option \[5\]. Of column II.
C. Recessive epistasis ratio: When recessive alleles at one locus mask the expression of both the dominant and recessive alleles at another locus, it is referred to as recessive epistasis. It is also known as supplementary epistasis. A good example of such a gene interaction is found in green colour in maize. Recessive epistasis ratio is \[9:3:4\].
C. Of column I matches correctly with option \[1\]. Of column II.
D. Dihybrid test cross ratio: Test cross is done to find out the genotype of the individual. Here, the individual is crossed with a recessive parent. Dihybrid test cross ratio is \[1:1:1:1\].
D. Of column I matches correctly with option \[2\]. Of column II.
E. Dominant epistasis ratio: Dominant epistasis occurs when the expression of one dominant or recessive allele is masked by another dominant allele. It is also known as simple epistasis. A good example of such a gene interaction is found in fruit colour in summer squash. Dominant epistasis ratio is \[12:3:1\].
E. Of column I matches correctly with option \[3\]. Of column II.

Therefore, Option B A-\[4\], B-\[5\], C-\[1\], D-\[2\], E-\[3\] is the correct answer.

Column I	Column II
A. Inhibitory gene ratio	\[4\]. \[13:3\]
B. Complementary gene ratio	\[5\]. \[9:7\]
C. Recessive epistasis ratio	\[1\]. \[9:3:4\]
D. Dihybrid test cross ratio	\[2\]. \[1:1:1:1\]
E. Dominant epistasis ratio	\[3\]. \[12:3:1\]

Note:
Mendelian genetics does not explain all types of inheritance for which the phenotypic ratios are different from Mendelian ratios. This happens because sometimes a particular allele may be partially or equally dominant to the other od due to existence of more than \[2\] alleles or due to lethal alleles. These kinds of genetic interactions between the alleles of a single gene are referred to as allelic or interallelic interactions.