Before understanding the concepts of genealogical DNA testing, it is important to understand the concepts of Deoxyribonucleic acid and chromosomes.
DNA and Chromosomes
Deoxyribonucleic acid (DNA) is the name given to the chemical that is present inside the nucleus of all cells and carries the genetic instructions for making living organisms. A normal Deoxyribonucleic acid molecule consists of two strands that are tightly wrapped around each other and resemble a twisted ladder.
The 'rungs' of the Deoxyribonucleic acid are made of chemicals that contain nitrogen and are called bases, while the sides are composed of sugar and phosphate molecules.
The four different types of bases present in the Deoxyribonucleic acid are adenine (A), cytosine (C), guanine (G), and thymine (T). The sequence is defined by the particular order of the bases that are arranged along the sugar - phosphate backbone.
Chromosomes are the thread like paired packages consisting of long segments of DNA that is contained inside the nucleus of each cell. In human beings, there are about 23 pairs of chromosomes. While, 22 pairs are essentially identical in the males and females. The 23rd pair is different.
In the females, this particular pair has two similar chromosomes, known as the X strand, while in males, this pair of chromosome contains a X strand and a Y strand, which are very different from each other. It is this pair of chromosome that determines the sex of any individual.
This test is performed to examine the nucleotides present in specific locations on an individual's DNA. These tests only provide genealogical information and are usually performed when you want answers to the following questions.
- Do you want to validate or invalidate your genealogical records?
- Do you believe that the spelling of your surname has been changed or somebody has been adopted into your family?
- Do you want to verify your relationship with a family that may have lived or is living in a region that you think you belong to?
- Do you think that you share a common ancestor with another individual or group?
The general procedure involved in a genealogical DNA test requires a buccal swab, which is a painless cheek scrap. These days, mouth wash or chewing gum too can be provided for testing purposes. The most common types are as follows.
Y Chromosome Testing
This is used when a man's paternal ancestry is to be traced. This procedure is also known as Y-STR testing, as the tests are performed on the Y chromosome of the men. The Y chromosome is used as it passes from the father to the son.
Women who want to determine their parental ancestry will have to request their father, brother, or any other male relative, who shares the same parental lineage, to take the test for them. In this procedure, segments of DNA on the Y chromosome are examined where the nucleotide segments are repeated. These segments are known as the 'genetic markers'.
Mitochondrial DNA Testing
It is used to trace an individual's maternal ancestry. The Deoxyribonucleic acid present in the human mitochondria is passed down from the mother to the child, without any changes. This procedure is also known as mtDNA testing.
mtDNA is divided into three regions, as per the current conventions, and the results are compared with the results of another person, to determine the time frame when the two people shared a most recent common ancestor (MRCA).
It is imperative that the reason behind getting a genealogical test done be a valid one. The outcome of these results have been known to upset people as they can prove if the father of a particular generation is not the same one as the one mentioned in the birth records. However, they are an excellent means for genealogical research.