question_answer

A dihybrid for qualitative trait is crossed with homozygous recessive individual of its type, the phenotypic ratio is [Orissa JEE 2005]

A) 1 : 2 : 1

B) 3 : 1

C) 1 : 1: 1 : 1

D) 9 : 3 : 3 : 1

Correct Answer: C

Solution :

A dyhybrid test cross give a 1:1:1:1 ratio indicating that two pairs of factors are segregation and assorting independently. Tt Rr × tt rr            TR     Tr       tR      tr TtRr - Tall Round Ttrr  - Tall wrinkle ttRr  - Dwarf Round ttrr   - Dwarf wrinkle 1 : 1 : 1: 1 Phenotypic ratio