The Alu Family
The Alu family is a family of repetitive elements in the human genome. Modern Alu elements are about 300 base pairs long and are therefore classified as short interspersed elements (SINEs) among the class of repetitive DNA elements. The typical structure is 5'Part A- A5TACA6 -Part B - PolyA Tail - 3', where Part A and Part B are similar peptide sequences, but of opposite direction. Expressed another way, it is believed modern Alu elements emerged from a head to tail fusion of two distinct FAMs (fossil antique monomers) over 100 mkya hence its dimeric structure of two similar but distinct monomers (left and right arms, and in opposite directions)joined by an A-rich linker. The length of the polyA tail varies between Alu families.
There are over one million Alu elements interspersed throughout the human genome, and it is estimated that about 10.7% of the human genome consists of Alu sequences. However less than 0.5% are polymorphic. In 1988, Jerzy Jurka and Temple Smith discovered that Alu elements were split in two major subfamilies known as AluJ and AluS, and other Alu subfamilies were also independently discovered by several groups. Later on, a sub-subfamily of AluS which included active Alu elements was given a separate name AluY. The discovery of Alu subfamilies led to the hypothesis of master/source genes, and provided the definitive link between transposable elements (active elements) and interspersed repetitive DNA (mutated copies of active elements).
Read more about this topic: Alu Element
Famous quotes containing the word family:
“What we often take to be family values—the work ethic, honesty, clean living, marital fidelity, and individual responsibility—are in fact social, religious, or cultural values. To be sure, these values are transmitted by parents to their children and are familial in that sense. They do not, however, originate within the family. It is the value of close relationships with other family members, and the importance of these bonds relative to other needs.”
—David Elkind (20th century)