Final answer:
The genotype is the genetic makeup determined by the combination of alleles inherited from one's parents, influencing the phenotype, or observable characteristics, of an individual.
Step-by-step explanation:
The term genotype defines the genetic makeup of an individual based on the genetic material (DNA) inherited from one's parents. The genotype includes the combination of alleles that an individual has for a particular gene. This genetic composition is represented by letter combinations, such as TT, Tt, and tt.
Organisms can be homozygous, possessing two identical alleles (BB or bb), or heterozygous, with two different alleles (Bb). The genotype is critical in determining the phenotype, which represents the observable characteristics of an individual, like hair color or height. However, the genotype comprises both expressed and non-expressed alleles that can influence these traits.