Correct option is C
The correct answer is (c).
Penetrance refers to the proportion of individuals with a particular genotype that actually express the corresponding phenotype. It measures the frequency with which a genotype manifests itself as a phenotype in a given population. For example, if a gene has 80% penetrance, 80% of individuals carrying the allele will express the phenotype, while the remaining 20% will not.
Incorrect options-
Option (a) is incorrect because a population of a diploid species can possess multiple allelic forms of a gene, not limited to only two. Although an individual diploid organism can carry only two alleles (one from each parent) for a given gene, the entire population may have many different alleles.
Option(b) is incorrect because in codominance, both alleles are expressed fully and equally in the heterozygote, not as an intermediate phenotype. The phenotype shows both traits simultaneously, unlike incomplete dominance where the phenotype is intermediate.
Option (d) is incorrect because expressivity is influenced by environmental factors and genetic background; it varies in the degree to which a phenotype is expressed among individuals with the same genotype.
