Discuss the gnetic basis of wrinkled phenotype of pea seed.

Introduction to alleles

Alternative forms of genes present on the same loci of homologous chromosomes are called alleles. For example, round (R) and wrinkled (r) alleles for seed shape of pea plants.

Genetic basis of wrinkled phenotype of pea seed

R and r are the alleles of the gene responsible for seed shape. R is the dominant allele and codes for round pea seeds whereas r is the recessive allele and codes for wrinkled pea seeds. Based on the presence of alleles, the expression of the traits differ as follows:

• RR (Homozygous dominant): Round seed
• Rr (Heterozygous dominant): Round seed, the expression of r is masked by R.
• rr (Homozygous recessive): Wrinkled seed

So, the wrinkled phenotype of pea seed is given by double recessive 'rr' genotype.