Final answer:
The student's question pertains to biology and the influence of alleles on genetic traits. Alleles are different versions of a gene, and a recessive allele requires two copies to express a trait, while a dominant allele can express a trait when present in a single copy. Understanding the combination of alleles is essential for predicting genetic traits.
Step-by-step explanation:
In biology, when discussing the inheritance of genetic traits, we often consider the role of alleles, which are different versions of the same gene. Diploid organisms, like humans, have two alleles for each gene - one inherited from each parent. Each allele is located on a chromosome, and the combination of alleles determines the organism's traits. A recessive allele only expresses its trait when an individual has two copies of that allele (homozygous). Whereas a dominant allele will express the trait even if only one copy is present in the genotype (heterozygous). Mendel's studies focused on peas with two allele forms, but we know now that there can be multiple alleles for a gene within a population. For example, blood types in humans show multiple allele patterns with A, B, and O alleles leading to combinations like AA, AB, or OO, determining different blood types.
The letter nomenclature used to denote alleles typically uses capital letters for dominant alleles and lowercase letters for recessive alleles. For example, in cat coat genetics, 'Mc' denotes a mackerel stripe pattern (dominant), while 'mc' denotes a classic tabby pattern (recessive). Thus, a homozygous recessive genotype would be 'mc/mc', indicating the cat displays the classic tabby pattern.
Knowledge of genetics and allele combinations allows us to predict the possible outcomes of an organism's traits. This fundamental concept is key to understanding inheritance patterns and genetic diversity within a species.