Question

distinguish between test cross and back cross​

Answer 1

Backcross

Test cross and backcross are two types of crosses introduced by Gregor Mendel. In test cross, a dominant phenotype is crossed with the homologous recessive genotype in order to discriminate between homologous dominant and heterozygous genotypes. In backcross, the F1 is crossed with one of the parents or genetically identical individual to the parent. The main difference between test cross and the backcross is that test cross is used to discriminate the genotype of an individual which is phenotypically dominant whereas a backcross is used to recover an elite genotype from a parent which bears an elite genotype.

This article explores, 

1. What is Test Cross

     – Definition, Function, Process

2. What is Backcross

     – Definition, Function, Process

3. What is the difference between Test Cross and Backcross

What is a Test Cross

The breeding of a dominant phenotype with the recessive phenotype is referred to as a test cross. Zygosity of the dominant phenotype can be identified by test cross. Zygosity is the degree of similarity between two alleles which determine a particular trait. The zygosity is identified by the proportion of phenotypes occurring in the offspring. It can be either homozygous or heterozygous. Homozygous individuals consist of either two dominant alleles or two recessive alleles. The heterozygous individuals contain both dominant and recessive alleles of the gene. 

If an individual exhibits the dominant phenotype, the genotype of that particular individual would be either homozygous dominant or heterozygous. In this situation, the exact genotype can be determined by performing a test cross with an individual exhibiting the recessive phenotype for that trait. The genotype of the recessive phenotype is always homozygous recessive for that particular trait. Therefore, the proportion of the phenotypes in the offspring may describe the zygosity of the dominant phenotype which is examined during the test cross.