Genetic variation refers to differences between members of the same species or those of different species. Genetic variation also refers to diversity in gene frequencies related to heredity of individuals. DNA is a biomolecule that holds the blueprint for how living organisms are built. DNA is made out of two long, twisted strands that contain complementary genetic information. A gene is a segment of DNA that is passed down from parents to children and confers a trait to the offspring. Genes are organized and packaged in units called “chromosomes.” Humans have 23 pairs of chromosomes. One set of chromosomes for each pair comes from a person’s mother, and the other set of chromosomes comes from the father.