The diploid condition in which the alleles at a given locus are identical is called homozygous or pulls. In homozygous condition, organism have two similar genes or alleles for a particular character in homologous pair of chromosomes, $e \cdot g .$, $TT$  or $tt.$

Organisms containing two different alleles or individual containing both dominant and recessive genes of an allele pair, $e . g ., \,Tt$ is known as heterozygous or hybrid