D-Loop
Definition
The non-coding displacement-loop control region of the mitochondrial genome (~bp 16024-576 in the rCRS). Contains the origin of replication and the promoters, and within it sit the hypervariable regions HV1 and HV2 targeted by forensic sequencing.
- Location
- Mitochondrial genome, ~bp 16024-576 rCRS
- Function
- Non-coding control region, replication origin
- Contains
- Hypervariable regions HV1 and HV2
- Forensic role
- Primary target of mtDNA sequencing
Common questions
Why is the D-loop the region targeted for forensic mtDNA sequencing rather than the whole mitochondrial genome?+
The D-loop's HV1 and HV2 segments accumulate sequence variation faster than coding mitochondrial regions because they are non-coding and under less selective constraint, so they carry the most population-level polymorphism per base sequenced, making them efficient for distinguishing maternal lineages with limited sequencing effort.
What does a D-loop match tell an investigator that nuclear STR profiling does not?+
Because mtDNA is maternally inherited and present in many copies per cell, D-loop sequencing can identify degraded samples such as old bone or hair shafts lacking nuclear DNA, but it only narrows identity to a maternal lineage shared by siblings and maternal relatives, not to a single individual the way STR profiling can.
Related terms
- Heteroplasmy
- The co-existence of two or more mitochondrial DNA sequence variants within a single individual, arising from somatic mutation or incomplete segregation. Length...
- Petrous Bone
- The petrous portion of the temporal bone, the densest bone in the human skull. Its dense hydroxyapatite matrix protects enclosed DNA from...
- Protamine
- Small arginine-rich proteins that replace histones in the nuclei of spermatozoa during spermatogenesis, producing a hyper-compacted chromatin structure approximately six times denser...
- rCRS
- The revised Cambridge Reference Sequence (GenBank accession NC_012920), the standard reference for human mitochondrial DNA. All mtDNA variant positions in forensic and...