Final answer:
An allele is a variant form of a gene, whereas genotype refers to the specific combination of alleles an individual possesses.
Step-by-step explanation:
The terms genotype and alleles are both crucial in understanding genetics. An allele is a variant form of a gene. Each gene may have multiple alleles accounting for genetic diversity within a population. In a diploid organism such as humans, one allele is inherited from each parent.
When it comes to a genotype, this refers to the specific combination of these alleles that an individual possesses. If a gene has two identical alleles, it is called homozygous, and if the alleles are different, it is heterozygous. The genotype is expressed through the phenotype, which is the observable traits of an individual.
A recessive allele only affects the phenotype if the organism is homozygous for that allele. This means that two individuals can exhibit the same phenotype but have different genotypes if one is homozygous dominant and the other is heterozygous. For example, a plant with a genotype TT or Tt will display the tall phenotype if 'T' represents the tall trait.