Understand that a genotype refers to the genetic constitution of an organism, specifically the alleles present at a given locus.
Recognize that the genotype is distinct from the phenotype, which is the observable characteristics or traits of an organism.
Consider that the genotype is responsible for the potential traits an organism can express, but the environment can influence the actual expression of these traits.
Identify that the genotype is often represented by letters (e.g., AA, Aa, aa) that denote the alleles inherited from the parents.
Conclude that the best definition of a genotype is 'The genetic makeup of an organism,' as it encompasses the complete set of genes and their variations within an organism.