D-loop is a Noncoding gene region in mtDNA. The function of D-loop is an unclear file. They said D-loop region is possiblely a control region in mitochondrial DNA (mtDNA) . Several consensus sequences has been found; they are TAS, CSB-I, II, III. These are believed about the regulation promoters of mtDNA. Below is the structure of Teleost fishes control region. Central domain is the most conserve region of this fragments.
This region is the most variable fragment in the mtDNA as we know. It can rutely separate into three part, Left domain, central domain and Right domain. Left domain length varies slightly lower than Right domain, and is a good region for us analyzing the phylogeny of intraspecies population, distingushing the much likely species in morphology level. In some low evolution rate species, scientists can resolve the interrelationship, even in family level, with central domain region.