What is co-dominance? Give one example.

Individuals receive one version of a gene, called an allele, from each parent. In a general condition, if the alleles are different, the dominant allele will be expressed, while the effect of the other allele, called recessive, is masked. In co-dominance, neither allele is recessive, and the phenotypes of both alleles are expressed. One example of co-dominance can be the ABO blood group. A person inheriting A and B alleles from both the parents will express both the alleles; thus, the blood group is stated as AB.

Define test cross and draw diagram.

A test cross is a method to test the genotype of hybrids obtained in a cross. In a test cross, the individual offspring of the F 1 generation is crossed with the homozygous recessive parent. Since the offspring is crossed back with one of the parents, it is also called back cross. It is used to test whether an individual is pure (homozygous) or hybrid (heterozygous). An example of a test cross: A tall (TT) and a dwarf (tt) plant are crossed to get a heterozygous tall (Tt) plant as the F 1 generation. In the test cross, the heterozygous tall plant (Tt) is crossed with the homozygous recessive parent (tt). The phenotypic and genotypic ratios are the same. i.e., 1:1.