The task is to identify and compare the mutant phenotypes. RNA can be translated into proteins on ribosomes. Proteins make the functional machinery of life. Most genes encode proteins. One gene determines one character.
Alleles are alternative forms of the gene.
Different alleles of one gene can impose different phenotypes. The genetic makeup of an organism is referred to as its genotype. The wild type allele specifies the phenotype 'purple', while a mutant allele, c2, specifies the lack of purple pigments. The character in question may be affected by more than one gene. The character would then be polygenic.