DNA Identification Matching and Mitochondrial DNA

One consumer vendor of DNA testing, Family Tree DNA, when they notify their customers of a match by email state:

When comparing the Hyper Variable Regions 1 and 2 of your mtDNA, a match has been found between you and another person(s) in the Family Tree DNA database. Matches of the mtDNA have more Anthropological significance as the time frame for a common ancestor could go beyond the Genealogical time frame.

Anthropological time for human mitochondrial DNA is essentially from about 200,000 years ago to the present. It is measured in age with relative measurements like carbon 14 testing rather than history.
The Genealogical time frame is the last portion of that since the beginning of the use of surnames. The extreme end of that is about 1000 years ago beginning with tracing lineages in royalty.

The formation of surnames began about 900 years ago and did not become common until about 400 years ago. James the Baker became James Baker. Fred the Blacksmith may have become Fred Black or Fred Smith.

Y Chromosome DNA, is passed on with a typical mutation rate of .02% or two in 10,000. As it is passsed by the male lineage, it tends to represent a paternal lineage that begins with a few mutations that coincide with the formation of surnames.

This is unlike the autosomal DNA used by the FBI which changes with each individual offspring and is a combination of genes from both parents.

Mitochondrial DNA (mtDNA), on the other hand, is passed from mother to daughter in the maternal lineage with a lower rate of mutation than the yDNA. While it is also passed from mother to son, that son does not pass his mtDNA to his offspring.

In one case, mtDNA of a 9,000 old "Cheddar Man" in the United Kingdom was traced down to a current resident of the UK teaching school in the area where Cheddar Man was found.

So, while two individuals may have the same mtDNA, it does not confirm they have a common ancestor within the timeline that surnames and genealogies have existed. If two individuals do not have the same mtDNA, therefore, it does exclude that possibility of a common ancestor.

The "Hyper Variable Regions" of the mtDNA are areas where the most, but not only, change occurs. The mtDNA can be thought as a circle or loop which breaks at the top during the process of reproduction.

The mitochondria are separate from the chromosomes and reproduce independently of them. There can be hundreds of mitochondria within one individual cell. Since there are so many copies of a relatively small chain of DNA, it is more easily tested.

Not all mtDNA testing is alike. For comparison, a full genome of mtDNA in humans is normally 16,569 base pairs of DNA. It is extremely small in comparison with the millions of base pairs in a single chromosome, of course. Consumers can have this tested for less than $500.This level of testing does give a level of resolution that indicates a particular maternal lineage.

Region one can be tested for less than $200 and both regions can be tested for less than $300. However, the testing done on both of the Hyper Variable Regions by consumers only covers only 1143 base pairs of that 16,569 base pairs. You could have differences outside those Hyper Variable Regions that occured over 60,000 years ago that are not detected by such testing. This level of testing does not give a level of resolution that indicates a particular maternal lineage.

However, this level of resolution is greater than the 721 base pairs used by the FBI. The mtDNA testing by the FBI is useful for exclusion if suspects, but it cannot be used to identify an individual as the one in an evidence sample.

Even if there is a "match" at that level of resolution, the suspect and the one the evidence sample came from could be not only separate individuals, but not even related for tens of thousands of years.

So, the use of mitochondrial DNA testing has its limits in genealogy and certainly in the courts.

Magic Trunks and the DNA "Gold Standard"

For those of you that have followed the Anthony case, what a magical trunk! It has all kinds of vapors and DNA that prove Caylee is dead. Not that that can be scientifically proven.

No DNA sample alone can prove the donor is dead. Nor can any vapor. If it smelled dead, likely an investigator had a bad meal as the same gases can be involved.

As far as googling for ways to create chlorophorm or breaking necks, that could have been done by the kidnapper(s) .

Supposing that a death HAS occured, that eliminates the aggravated murder because the chlorophorm causes the heart to stop while unconcious.

If you mix chlorine (bleach) and acetone (nail polish remover) or isopropal alcohol (rubbing alcohol) this can accidently produce chlorophorm. Obviously, a child can do this - or an adult by accident.

The more I read these articles, the less I trust the AP, the media who copy them, or the prosecutor for eliminating the alternative hypothesis.

The DNA in this case was a "high resolution" test of the mitochondrial DNA. I have had this test. I have over 278 matches at http://www.familytreedna.com/ .

That was part of a full genome sequence (FGS) of my mitochondrial DNA, which I have no matches to in a database of over 80238. I have a copy of the report. Their DNA test is of less than 1319 base pairs. My test was of 16,570 base pairs. (I have one insertion more, which is not rare.) This means my FGS has 12 times more resolution than the FBI test.

I read a Certificate of Analysis from the Virgina Deparment of Forensic Analysis which used 16 markers instead of the 13 that the FBI does for more resolution. The technition said:

This information is provided only as an investigative lead, and any possible connection or involvement of this individual to this case must be determined through futher investigation.

SO, these tests are not the end all in investigations. They add to the proponderence of evidence, but they do not make a case "beyond a reasonable doubt."

Whenever I find that DNA testing is being done, I want to know:

What were the DNA tests that were run?

In the CODIS database of Maryland , of fewer than 30,000 profiles, 32 pairs matched at nine or more loci. Three of those pairs were "perfect" matches, identical at 13 out of 13 loci. Experts say they most likely are duplicates or belong to identical twins or brothers, but they did not establish that.

A study of the Arizona CODIS database carried out in 2005 showed that approximately 1 in every 228 profiles in the database matched another profile in the database at nine or more loci, that approximately 1 in every 1,489 profiles matched at 10 loci, 1 in 16,374 profiles matched at 11 loci, and 1 in 32,747 matched at 12 loci.

In a case against a Murillo-Sosa, a jury was told the match was 5 of 13. They had to say he was not guilty. SO, what kind of matches are they making? How about doing it right the first time and take the time to get a FULL DNA testing of Y chromosome DNA and mitochondrial DNA, as well as autosomal (CODIS) DNA?

Is it a mitochondrial DNA test which matches everyone who descended from the same maternal ancestor in the last 20 generations as THE DEFENDENT(S) ? Is it just a "high resolution test" which the FBI performs or a real full genome sequencing of the mitochondrial DNA?

Is it a Y Chromosome test which matches everyone who has the same paternal lineage for the past 400 years? If so, is it 12 markers, which could be one to fifty percent of the population, or is it a 67 marker test that can pin it down to a surname?

There may be a way to combine all of these that will resolve the identity to one person, but is what they have beyond a reasonable doubt unless they do FULL testing?