Final answer:
In peas, the recessive allele (r) does not express functional traits, because of a latent unit factor. The recessive allele is only observed in homozygous recessive individuals. For example, in the trait of flower color in pea plants, a plant with the genotype Yy will have yellow flowers because the dominant allele is expressed, while a plant with the genotype yy will have green flowers because there are no dominant alleles to be expressed.
Step-by-step explanation:
In peas, the recessive allele (r) does not express functional traits, because of a latent unit factor.
The recessive allele is one that is not expressed in heterozygous individuals, meaning those that have one dominant and one recessive allele. It is only observed in homozygous recessive individuals, who have two copies of the recessive allele.
For example, if we consider the trait of flower color in pea plants, where the dominant allele (Y) produces yellow flowers and the recessive allele (y) produces green flowers, a plant with the genotype Yy will have yellow flowers because the dominant allele is expressed, while a plant with the genotype yy will have green flowers because there are no dominant alleles to be expressed.