Question

The genotypes AaBB : AaBb : Aabb: aabb are obtained, From a cross AABb × aaBb, in the ratio:
A. 1:1:1:1
B. 1:2:1:0
C. 0:3:1:0
D. 1:1:1:0

Answer 1

Hint: A genotype is defined as an organism’s set of heritable genes. That is passed down from parents to offspring. The three types of genotypes are homozygous dominant, homozygous recessive, and heterozygous. A genetic cross is defined as the purposeful mating of two individuals resulting in the combination of genetic material in the offspring.

Complete answer:
> A genotype is an individual's collection of genes. It can refer to the two alleles inherited for a particular gene. When the information encoded in the DNA, it is used to make protein and RNA molecules, the genotype is expressed.
> Offspring that carry part of the genetic material of each parent, The deliberate breeding of two different individuals. The parent organisms may be from different varieties or closely related species must be genetically compatible.
> In the cross AABb X aaBb, genotype aabb is not obtained and the genotypes obtained are AaBB, AaBb, and Aabb in a ratio of 1:2:1. The phenotypic ratio will be 3:1.

Hence, the correct answer is 'B'.

Additional Information:
> The 1:1:1:1 phenotypic ratio is the classic Mendelian ratio for a test cross in which the alleles of the two genes assort independently into gametes (AaBb × aabb).
> The 9:3:3:1 phenotypic ratio is the classic Mendelian ratio for a dihybrid cross in which the alleles of two different genes assort independently into gametes.

Note: From AABb, there are four gametes AB AB Ab Ab, and from aaBb, we got four gametes aB aB ab ab and then if we do a cross between these gametes by using punnett square we get 4 - AaBB, 8 - AaBb, and 4 - Aabb individuals, 0 -number of AABB individuals, respectively. Hence, the resultant ratio 1:2:1:0.