Dna Chemical Markers

DNA tests reveal relationships between people by analyzing the similarities between the chemical markers on their unique DNA strands. By taking DNA tests, two people can find out whether or not they are related.

DNA Defined

DNA is the genetic material that controls inherited traits in living creatures. Our DNA determines characteristics such as:

  • bone structure and density
  • eye color
  • facial features
  • hair color and texture
  • height
  • skin color.

We carry DNA in almost all of our bodies” cells with the exception of our red blood cells. The most common way to get a DNA sample for testing is by gathering a sample of saliva with a painless swab of the inside of the cheek.

The two main types of DNA tests that can help trace genealogy include mtDNA tests and Y Line tests.

mtDNA Tests

An mtDNA test looks at mitochondrial DNA (mtDNA) to determine relationships and family history. Mitochondrial DNA is a chemical marker for DNA that is found in the cell”s cytoplasm, rather than its nucleus.

MtDNA passes unchanged from a mother to both her sons and daughters. While mtDNA is passed from a mother to her son, the son does not pass this chemical marker for DNA to his offspring. As a result, because mitochondrial DNA changes very slowly over time, this type of DNA test can determine a consistency in the maternal line, revealing whether two people share a maternal ancestor.

MtDNA tests involve sequencing the HVR-1 and/or HVR-2 regions, assigning people to a maternal haplogroup (a genetic population defined by a pattern of chemical markers). If two people want to determine whether they are related or want to know more about their maternal ancestry, mtDNA tests can be quite effective.

However, while a match on an mtDNA test shows that two people have a common ancestor, it can not determine whether that ancestor was from the last generation or a hundred years ago. Similarly, this type of DNA test can”t tell people how they are related. For example, although mtDNA test can identify that people are of the same maternal bloodline, they won”t know whether they are cousins or some other relation based alone on mtDNA test results.

Y Line Tests

Y Line tests analyze the DNA chemical markers contained in the nucleus of cells on the Y chromosome. In contrast to mtDNA tests, these chemical markers form a pattern that can define a paternal haplotype or male lineage.

Y Line studies use short tandem repeat (STR) and single nucleotide polymorphism (SNP) testing of the Y chromosome. While shared markers indicate that two individuals are related, this type of DNA test, like the mtDNA test, can not determine the exact relationship that two individuals share.

Y Line DNA tests are useful for:

  • determining paternal lineage
  • finding out if a man is related to another man with the same last name
  • males only.

In general, experts recommend pairing traditional research with Y line DNA tests.

Online Testing Services

In recent years, online testing services have become available for people who would like to know more about their origins and family.These services differ from traditional testing laboratories in that everything is done online and through the mail, eliminating the need to visit a laboratory for testing.

Choosing an Online DNA Testing Service

If you decide to explore your origins through an online DNA testing service, do some research to make sure the lab you have chosen is accurate and legitimate. Two important certifications to look for are:

  • accreditation from the American Association of Blood Banks
  • ISO 17025 certification.

Both of these organizations take the time to inspect the labs they certify and perform regular audits to be sure that high standards are maintained. Other important factors to consider when choosing a lab include:

  • checking for hidden fees
  • determining if the lab offers the type of testing you want
  • understanding the privacy policy of the lab.

Resources

Powell, Kimberly (2008). DNA Family Trees. Retrieved March 12, 2008, from the About.com Web site.

Riley, Donald E. (2005). DNA Testing: An Introduction For Non-Scientists An Illustrated Explanation. Retrieved March 12, 2008, from the Scientific Testimony: An Online Journal Web site.

Science Articles, Physics Post (2008). Things to know before selecting an online DNA testing service. Retrieved March 12, 2008, from the Physics Post Web site.