Mitochondrial DNA

Mitochondrial DNA (Mt DNA) is the DNA located in the mitochondria and is energy producing cell organelle.

It consists of a small and circular genome. MtDNA has about 16569 bps and 37 genes that code for products which are used in cellular energy production.

It is not unique as compared to nuclear DNA and is identical in all maternity relatives. Mitochondrial DNA is inherited strictly from one’s mother. During fertilization only sperm’s nuclear enter the egg and fuses with egg’s nucleus. Therefore, mtDNA of female get transferred to offspring without any male influence.

Presence of ubiquitin tag during spermatogenesis destroys any of the sperm mitochondria which enter the egg. Since, it is not unique, mtDNA cannot be used for individual’s identification during mass disasters or missing person’s identification but it can be reduce the significance of the match in forensic cases.

The occurrence of a match between a person’s mtDNA found at a crime scene only implies their presence there, rather than confirming it. In additional, maternally related individuals usually have the entire mtDNA sequence in common, meaning it is impossible to distinguish between their mtDNA samples.

Polymerase chain reaction amplification is usually carried out on a sample of mtDNA to increase the amount of DNA available for analysis, followed by techniques such as Sanger sequencing.

Authored by

Darshana Gupta (M.Sc. Forensic Science)