Genetics To use the sharing features on this page, please enable JavaScript. From Genetics Home Reference. Learn more Find consumer-friendly information about the effects of genetic variation on human health. Genetic Conditions Learn about the signs and symptoms, causes, and inheritance of more than 1,300 health conditions with a genetic basis. Genes Find information about the function of more than 1,400 genes and see how changes in these genes are related to health conditions. Chromosomes and mtDNA Read about each of the 23 pairs of human chromosomes and mitochondrial DNA (mtDNA). Help Me Understand Genetics Explore topics in human genetics, from the basics of DNA to genomic research and personalized medicine.