Genotype and phenotype
In diploid cells, homologous chromosomes provide two copies of a gene at corresponding loci. The alleles present at a particular locus form part of an organism's genotype.
Genotype describes the alleles an organism possesses. For one gene, this may be written as combinations such as AA, Aa or aa.
Phenotype describes the observable characteristics of an organism. These characteristics result from its genotype together with environmental influences.
| Term | What it describes | Example |
|---|---|---|
| Genotype | The alleles present | AA or Aa |
| Phenotype | The observable characteristic | Black coat |
Two organisms can therefore show the same phenotype while having different genotypes when a dominant allele is involved.