Question

When two hybrids Ttrr and Rrtt are crossed, the phenotypic ratio of offspring shall be
(A) 3:1
(B) 1:1:1:1
(C) 1:1
(D) 9:3:3:1

Answer 1

The relative number of offsprings shown by a combination of trait is called phenotypic ratio.Through the test cross method it can be determined and the frequency of the combination of trait is expressed by the genotype of the offsprings.

Complete answer:
Ttrr is formed by two gametes that are tr which means tall plants and Tr means wrinkled seed plants. Rrtt is also formed by two gametes that are Rt which is round seed plant and rt means dwarf plant.
When Ttrr and Rrtt is crossed the obtained phenotypic ratio will be

The phenotypic ratio will be 1:1:1:1
The random fusion of gamete from Ttrr and Rrtt produces four genotypes

ttRr ( dwarf plants with round seed)
TtRr ( tall plant with round seed)
ttrr ( dwarf plant with wrinkled seed)
Ttrr ( tall plant with wrinkled seed)

Additional information :
A cross between an organism which is heterozygous for one or more genes and an organism that is homozygous for the recessive alleles. A test cross method is very useful for genetic analysis. Test cross method is used to test an genotype of an individual by crossing it with an individual of known genotype.

Note: Mendal was the first scientist to study the pattern of inheritance. He is also known as the father of genetics and proposed the law of inheritance.