Question

Match the genetic phenomena with their respective ratios.

	List I		List 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	9:7
E	Dominant epistasis ratio	5	13:3

• 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

Answer: (E)

a- 5, b- 4, c- 1, d- 2, e- 3

• For inhibitory genes (suppressor genes): A suppressor is an allele that reverses the effect of a mutation of another gene, resulting in the normal (wild-type) phenotype.
  
• For complementary genes, both dominant alleles of the 2 genes are needed to express a given phenotype and result in a ratio of 9:7. The 9 all have at least one copy of both dominant alleles (e.g., A+B) - the 7 have either no dominant alleles (aabb),or (A-bb) or (aaB-).
  
• For recessive epistasis, the phenotypic ratio is 9:3:4 (here the homozygous recessive allele for a gene (the epistatic gene) masks the expression of the dominant allele for another gene (the hypostatic gene).
  
• Dihybrid test cross ratio: A 1:1:1:1 ratio in a testcross of a dihybrid and a 9:3:3:1 ratio in a self of a dihybrid both reflect a gametic ratio of 1:1:1:1, which shows the allele pairs are assorting independently (generally because they are on different chromosome pairs) and that the RF is 50 percent.
  
• Dominant epistasis ratio: A mutation that exerts its expression by canceling the expression of the alleles of another gene caused by the dominant allele of one gene, masking the action of either allele of the other gene. The ratio is 12:3:1.

  So, the correct answer is '		a- 5, b- 4, c- 1, d- 2, e- 3'