There are always two copies of each gene, one from each parent. A gene, however, can have different versions, called alleles. Alleles are various versions of a gene. The combination of alleles inherited from the parents is what gives rise to genotypes.

How does genotype happen?

This happens because genes have different alleles. For some genes and traits, certain alleles are dominant while others are recessive. A dominant trait is one that shows up in an individual, even if the individual has only one allele">allele that produces the trait.

Where does each allele in a genotype come from?

An individual inherits two alleles for each gene, one from each parent. If the two alleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous.