However, many chloroplasts and mitochondria have a linear chromosome, and D-loop replication is not important in these organelles.
[1] In many organisms, one strand of DNA in the plasmid comprises heavier nucleotides (relatively more purines: adenine and guanine).
[3][4] When diagramed, the resulting structure looks like the letter D. The D-loop was first discovered in 1971 when researchers noticed that many DNA in the mitochondria they were examining under microscope contained a short segment that was tripled stranded.
[10] One example of the use of D-loop mutations in phylogeographic studies was the phylogeny assembled using the highly unstudied red deer on the Iberian peninsula.
[11] In another example, scientist used the variations in the D-loop, along with microsatellite markers, to study and map out the genetic diversity among goats in Sri Lanka.