Mitochondrial Analysis

Mitochondrial DNA analysis is a type of test using genetic material passed only from mother to child. It has become increasingly popular in law enforcement applications.

Most genetic tests use samples taken from the cell's nucleus. Mitochondrial analysis differs by using DNA extracted from another cellular organelle called a mitochondrion. Also called mtDNA, this material is carried in a mother's egg cell and passed unchanged to her offspring. A father's sperm cell contributes only nuclear DNA. In addition to tracking matrilineal ancestry, mtDNA can be used to identify individuals through a unique genetic fingerprint.

Advantages of Mitochondrial DNA Analysis

Mitochondrial DNA analysis is so effective because it can examine the DNA from samples that cannot be analyzed by other test methods such as RFLP or STR.

This flexibility is particularly helpful for older forensic investigations where soft tissue samples are no longer available. Unlike nuclear DNA, mitochondrial DNA can be extracted from:

• bones
• hair
• teeth.

Comparing the mtDNA profile of unidentified remains with a potential maternal relative can be extremely important in missing-person investigations, helping families receive closure about their loved ones. Mitochondrial Analysis was among the DNA techniques used for identifying 9/11 victims.

Mitochondrial DNA analysis is also a powerful tool for tracking ancestry through female lineages over hundreds of generations. In anthropological studies, mtDNA can reveal important and fascinating information about the lives of those from ancient civilizations.

Mitochondrial Mutations

Over many generations, our mtDNA changes or mutates. Most of these mutations are harmless and enable scientists to track matrilineal ancestry. Occasionally a mutation can cause a serious health problem. A few conditions caused by mutations of mitochondrial DNA include:

• exercise intolerance
• Kearns-Sayre syndrome (KSS) which causes loss of proper functioning in the eye, heart and muscles.

All About Eve

Mitochondrial Eve is the name given by scientists to the woman who is defined as most recent matrilineal common ancestor for all living humans. Passed down through each mother to her offspring, Eve's mitochondrial DNA is now found in all living humans. She is believed to have lived about 140,000 years ago in what would now be one of three countries in Africa:

• Ethiopia
• Kenya
• Tanzania.

Other DNA Testing Methods

DNA analysis mitochondrial is one of many important genetic testing methods. Some other widely used techniques include:

• Polymerase Chain Reaction (PCR): PCR is used to make millions of exact copies of DNA from a biological sample. DNA amplification with PCR allows biological samples as small as a few skin cells to be analyzed.
• Restriction Fragment Length Polymorphism (RFLP): This is a technique for analyzing the variable lengths of DNA fragments that result from digesting a DNA sample with a special kind of enzyme.
• Short tandem repeat (STR): STR technology evaluates repeating base pairs on specific regions of nuclear DNA. Variability in STR regions can distinguish one DNA profile from another.

Mitochondrial DNA from Dad

It is widely understood that in humans, mitochondrial DNA can only inherited maternally. The same holds true for most animal species. There are, however, a few fascinating exceptions to this rule. Paternally inherited mtDNA has occasionally been found in:

• cloned cattle
• fruit flies
• honeybees
• mussels
• sheep.

There has also been a single case of paternally inherited mtDNA in a human male, which was linked to infertility.

Resources

Answers.com (n.d.). Mitochondrial DNA. Retrieved September 2, 2008, from answers.com Web site: http://www.answers.com/topic/mitochondrial-dna.

Human Genome Project Information (n.d.). DNA Forensics. Retrieved September 2, 2008, from Human Genome Project Information Web site: http://www.ornl.gov/sci/techresources/Human_Genome/elsi/forensics.shtml.