Geneotype with different alleles
Allele
Homozygous
Heterozygous
Dominant
Recessive
A genotype with different alleles refers to having two different forms of a gene at a particular locus on a chromosome.
Homozygous refers to having two identical alleles for a specific gene. For example, if an individual has two dominant alleles (AA) or two recessive alleles (aa), they are homozygous for that gene.
Heterozygous refers to having two different alleles for a specific gene. For example, if an individual has one dominant allele and one recessive allele (Aa), they are heterozygous for that gene.
The dominant allele is the form of a gene that is expressed, or "wins" over the recessive allele in terms of phenotype. It will usually mask the effects of the recessive allele. It is represented by a capital letter in genetic notation.
The recessive allele is the form of a gene that is only expressed when an individual has two copies of it (homozygous recessive). It is represented by a lowercase letter in genetic notation.