Genetic terms

Genotype is the genetic composition of an organism.
Phenotype is the set of characteristic manifested by an organism.
An individual has a heterozygous condition if he has 2 different alleles of the same gene
An individual has a homozygous condition if he has 2 identical alleles of the same gene.
Codominance is a genetic interaction where the codominant alleles of a gene express themselves equally in the phenotype
Dominance is a genetic interaction where 1 allele of a gene masks the expression of another allele in the heterozygote.
Locus is the position of a gene in a DNA molecule of a chromosome
A gene is the functional unit of inheritance
An allele is an alternative form of a gene.