Question

In a plant, red fruit (R) dominates 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.
A. 75\[\% \] will be tall with red fruit.
B. All the offspring will be tall with red fruit.
C. 25\[\% \] will be tall with red fruit.
D. 50\[\% \] will be tall with red fruit.

Answer 1

Hint:-The genotype is defined as the heritable pair of a gene that is the genetic makeup of an individual organism and passed from one generation to another. These genes play a role in specifying the factors that are visible in an individual like hair colour, height, etc. Phenotype is defined as the physical appearance of an individual as distinguished from its genetic makeup.

Complete Answer:-
The genotype is of types: Homozygous dominant, Homozygous recessive, and Heterozygous.
In RRTt, both R and T are dominant while t is recessive. So, T overcomes the effect of t. Hence the plant is tall with red fruit. This is a case of heterozygous.
In rrtt, both r and t are recessive. Hence the plant is dwarfed with yellow fruit. This is a case of homozygous recessive.

Parent generation: RRTt (red tall) $ \times $ rrtt (yellow dwarf)


Gametes: RT Rt rt rt
$F1$ generation:

RrTt	Rrtt
RrTt	Rrtt

RrTt (red fruit and tall plant)
Rrtt (red fruit and dwarf plant)
The phenotypic ratio will be 1: 1 (Red fruit and tall plant: red fruit and dwarf plant)
All plants are red. Hence 50 per cent plants are red tall and 50 per cent plants are red dwarf.
So, the correct answer is option D.

Note:- Homozygous is a defined percent condition in which both the pair of chromosomes or gene have the same genetic sequence. In simple words, it is the degree of similarity in the alleles. Heterozygous is defined as the condition in which both the pair of chromosomes or gene has a different genetic sequence (one wild type and one mutant allele).