The genetic constitution of an organism, also known as its genotype, is the set of genes that it carries. It is the genetic makeup of an organism that determines its physical characteristics and traits. Genotypes are inherited from parents and can be passed down to offspring. The genotype of an organism is determined by the combination of alleles it carries, which are variations of a gene. Alleles can be dominant or recessive, and the combination of alleles determines the phenotype, or physical characteristics, of an organism.