Melanin, the skin’s brown pigment, is a natural sunscreen that protects tropical peoples from the many harmful effects of ultraviolet (UV) rays. But when UV rays penetrate the skin they also produce beneficial vitamin D, so some exposure to them is necessary. This delicate balancing act explains why the peoples that migrated to darker, colder climes developed lighter skin color. As people moved to areas with lower UV levels, their skin lightened so that UV rays could penetrate and produce essential vitamin D. In some cases a third factor intervened: Coastal peoples who eat diets rich in seafood enjoy an alternate source of vitamin D. This is why some Arctic peoples, for example, can afford to remain dark-skinned even in low UV climes.
Remnants of ancient parasitic bacteria that now help to produce energy inside the cell. A mitochondrion has its own genome, present in only one copy, which does not recombine in reproduction. This genetic consistency makes mitochondrial DNA a very important tool in tracking genetic histories.
Mitochondrial DNA, or mtDNA, is contained in your cells’ mitochondria—the energy producers. Mitochondrial DNA is passed virtually intact from mothers to their children. The genetic markers found on mtDNA make it a useful molecule to trace your maternal ancestry.
A mutation is a mistake, or “typo,” in your DNA. When you have a child, your DNA is copied and passed on to that child, which is why children often look like their parents. Occasionally, however, there are mistakes made, and a mutation arises that makes each generation slightly different from the one before. If you and someone else have the same mutations, you share a common ancestor who was the first to have that mutation in their DNA, which was then passed on to you. In this manner, mutations can serve as genetic markers of descent, and from them we can build a family tree for everyone alive today.
The vast majority of your genome (apart from mtDNA) that is found in the cell nucleus
A DNA building block that contains a base, or half of a “staircase step,” as well as sugars and phosphates that form the “railing.” Nucleotides join together to form DNA’s distinctive double helix shape.
The part of the cell in which chromosomes reside
The evolutionary development of a species. Phylogeny is sometimes represented as a tree that shows the natural relations and development of all species. It can also be applied to the evolutionary tree of a specific region of DNA, in particular the Y-chromosome and mtDNA.
The study of genetic variation in a species
A linear sequence of amino acids that is the building block of cells. Each protein has a specific function that is determined by the “blueprint” stored in DNA.