Question

Differentiate between.
Back cross and test cross

Answer 1

The main difference between a back cross and a test cross is their function. Also, the crossing takes place between two different generations, so the parent crossing has a significant role in the outcome of the cross. Therefore, this is also a place of difference between both the crosses.

Complete answer:
The major differences between the back cross and test cross are as follows:

BACK CROSS	TEST CROSS
The cross between the $F_1$ progeny and any one of its parents is known as a back cross.	The cross between the $F_1$ progeny and the recessive phenotypic parent is known as a test cross.
Back crosses can only be referred to as a test cross if done with the recessive parent. Otherwise, all backcrosses are not tested crosses.	All test crosses are backcrosses.
The parent with which the $F_1$ progeny is crossed can either be homozygous dominant or heterozygous dominant.	The parent with which the $F_1$ progeny is crossed is always homozygous recessive.
Back cross helps in identifying the elite genotypes by checking the segregation of genes at the time of gamete formation.	Test cross helps in identifying the genotype of the dominant individual.

If the test cross is heterozygous dominant, then crossing it with the recessive parent will produce a recessive product. But if the test cross is homozygous dominant, then the cross with the recessive parent will not produce any recessive product.

Note:
In animals, this back cross is referred to as the top cross. The term test cross and back cross were coined by Gregor Johann Mendel when he was performing his studies on genetics.
Zygosity refers to the proportion of individuals that can be either homozygous and heterozygous. A heterozygous genotype has a dominant and a recessive allele in their genotype. Homozygous genotype has either both dominant alleles or both recessive alleles.