PATHOLOGY

Detailed explanation-1: -A homozygous recessive allele combination contains two recessive alleles and expresses the recessive phenotype. For example, the gene for seed shape in pea plants exists in two forms, one form (or allele) for round seed shape (R) and the other for wrinkled seed shape (r).

Detailed explanation-2: -Individuals carrying two identical alleles (RR or rr) are known as homozygous. While individual organisms bearing different alleles (Rr) are known as heterozygous.

Detailed explanation-3: -The combination of alleles carried by an individual is its genotype. For example, let’s say R (read “big R”) is the dominant round allele, and r (read “little r”) is the recessive wrinkled allele. True-breeding round peas would have two copies of the R allele and a genotype of RR.

Detailed explanation-4: -Dominant and Recessive Alleles If the genotype for seeds was Rr (where R is dominant and r is recessive), R would supersede the recessive gene and the plant would express a round seed phenotype.