Final answer:
A recessive allele is represented by a lowercase letter, and a recessive trait will be observed in individuals that are homozygous for the trait.Thus the correct option is a.
Step-by-step explanation:
A recessive allele is usually represented as a lowercase letter. In genetic nomenclature, alleles producing dominant traits are denoted by initial capital letters; those that confer recessive traits are written with lowercase letters. For example, in cat coat genetics, the allele for a mackerel-striped pattern is indicated as 'Mc', which is dominant, and the allele for a 'classic' or 'oyster tabby' pattern as 'mc', which is recessive. Therefore, a classical-pattern tabby cat would carry the alleles 'mc/mc', being homozygous for the recessive trait. A recessive trait will be observed in individuals that are homozygous for that trait (c), as they need two copies of the recessive allele to express the phenotype.