Question

what is test cross? how does it differ from reciprocal cross.

Answer 1

The major difference between these two types is that a test cross is carried out to determine the zygosity of the parent; whereas, a reciprocal cross is used to determine the role of parental sex in the inheritance of a trait, i.e., if the trait is sex-linked.

Answer 2

This type of genetic cross was first conducted by Gregor Mendel in his experiments with pea plants, and it involved the crossing or mating of an individual with an unknown genotype, displaying a dominant phenotype with another individual who had a homozygous recessive phenotype and genotype. The characteristics of the progeny produced from such a breeding would help in determining the zygosity of the parent with respect to a particular gene or trait. Zygosity refers to the similarity between the various alleles of the same gene, and an organism can be heterozygous (dissimilar alleles) or homozygous (identical alleles) for a given gene.

In simple genetic inheritance, any allele for a gene is either dominant or recessive. The presence of even a single dominant allele results in a dominant phenotype, i.e., the dominant characteristic of the gene is displayed when the organism is either homozygous or heterozygous. In comparison, the recessive allele requires a homozygous genotype in order to express the features associated with it. Hence, it can be concluded that a recessive phenotype is always due to a homozygous genotype, but a dominant phenotype may be due to either a homozygous or a heterozygous genotype.

This conclusion is the rationale behind conducting a test cross. The progeny produced from a test-crossed individual is examined, and the pattern of phenotype displayed by the progeny helps determine the genotype of that individual.
I hope it will help u....