Homozygous:

(i) It is pure for a trait and breeds true i.e., gives rise to similar homozygous individuals.

(ii) Both the alleles of a trait are similar, e.g., TT, tt.

(iii) Homozygous individual can carry either dominant or recessive alleles but not both.

(iv) It produces one type of gametes.

(v) It does not show extra vigour.

Heterozygous:

(i) Heterozygous individual is seldom pure and produces offspring with different genotypes on selfing. e.g., TT, Tt and tt on selfing of Tt individuals.

(ii) It carries dissimilar alleles, e.g., Tt

(iii) Heterozygous individual has both dominant and recessive alleles.

(iv) It produces two types of gametes.

(v) The individual can show extra vigour called hybrid vigour or heterosis.