Question

In a plant, red fruit (R) is dominant over yellow fruit(r) and tallness (T ) is dominant over shortness(t). If a plant with RRTt genotype is crossed with a plant that is rrtt then
A. 25% will be tall with red fruit
B. 50% will be tall with red fruit
C. 75% will be tall with red fruit
D. All the offspring will be tall with red fruit

Answer 1

Hint: The organism which has two different alleles of a gene is called a heterozygous organism. In a heterozygous gene the trait which is expressed is known as a dominant trait whereas the other allele which is unexpressed is known as recessive.

Complete Answer:
The cross in which two different genes which show different characters are taken is known as dihybrid cross. It was first demonstrated by Mendel in a pea plant.
According to the question,
- Red fruit represented by gene (R) is dominant over yellow fruit represented as (r).
- Tallnes(T) is dominant over shortness(t).
- The cross between RRTt X rrtt. The male gametes are RT and Rt.
- The female gamete is represented as rt.

	RT	Rt
rt	RrTtRed, tall	RrttRed, short

The offsprings produced are 50% red and tall and 50% red and short.

So the correct answer for this question is option B.

Note: In gamete formation, each gamete receives one copy of the gene which is selected randomly. This is called the law of segregation. The alleles of different genes assort independently into gametes. This is known as the law of independent assortment. The classic phenotypic ratio of Mendalian dihybrid cross is 9:3:3:1.