Haplogroup E-M215 (Y-DNA)

In human genetics, Y Haplogroup E-M215, also referred to in the literature by other names such as E1b1b and E3b (see further discussion below), is a major Y-chromosome haplogroup. It is a division of the macro haplogroup E-M96, which is defined by the single nucleotide polymorphism (SNP) mutation M215. In other words, it is one of the major paternal lines of humanity, linking from father-to-son back to a common male-line ancestor. It is a subject of discussion and study in genetics as well as genetic genealogy, archaeology, and historical linguistics.

E-M215 has two ancient branches that contain all known modern E-M215 men, E-M35 and E-M281. Of these two, the only branch that has been confirmed in a native population outside of Ethiopia is E-M35, which in turn has two known branches, E-V68, E-Z827 which contain by far the majority of all modern E-M215 men. E-V68 and E-V257 have been found in highest numbers in North Africa and the Horn of Africa; but also in lower numbers in parts of the Middle East and Europe, and in isolated populations of Southern Africa.

Y chromosome

The Y chromosome is one of two sex chromosomes (allosomes) in mammals, including humans, and many other animals. The other is the X chromosome. Y is the sex-determining chromosome in many species, since it is the presence or absence of Y that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which triggers testis development. The DNA in the human Y chromosome is composed of about 59 million base pairs. The Y chromosome is passed only from father to son. With a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest evolving parts of the human genome. To date, over 200 Y-linked genes have been identified. All Y-linked genes are expressed and (apart from duplicated genes) hemizygous (present on only one chromosome) except in the cases of aneuploidy such as XYY syndrome or XXYY syndrome. (See Y linkage.)

Overview

Discovery

The Y chromosome was identified as a sex-determining chromosome by Nettie Stevens at Bryn Mawr College in 1905 during a study of the mealworm Tenebrio molitor. Edmund Beecher Wilson independently discovered the same mechanisms the same year. Stevens proposed that chromosomes always existed in pairs and that the Y chromosome was the pair of the X chromosome discovered in 1890 by Hermann Henking. She realized that the previous idea of Clarence Erwin McClung, that the X chromosome determines sex, was wrong and that sex determination is, in fact, due to the presence or absence of the Y chromosome. Stevens named the chromosome "Y" simply to follow on from Henking's "X" alphabetically.