Final answer:
Genotype refers to the combination of alleles that an organism has for a certain gene, while phenotype describes the observable traits expressed by an organism. In diploid organisms, homozygous individuals have two of the same alleles for a gene, while heterozygous individuals have two different alleles.
Step-by-step explanation:
Genotype and Phenotype
Genotype is a way to describe the combination of alleles that an individual has for a certain gene. For each gene, an organism has two alleles, one on each chromosome of a homologous pair of chromosomes. The genotype is represented by letter combinations, such as TT, Tt, and tt.
Phenotypes and Genotypes
The observable traits expressed by an organism are referred to as its phenotype. An organism's underlying genetic makeup, consisting of both physically visible and non-expressed alleles, is called its genotype. When two alleles for a given gene are the same, the organism is homozygous, and when they are different, the organism is heterozygous.