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Use DNA Testing to Determine Your Ancestry

Learn How Y-DNA, mtDNA and Autosomal DNA Testing are used by Genealogists to Discover Ancestry

Genetic Genealogy is the application of DNA testing to determine the level of relationships among individuals. There are currently three Ancestry DNA or Genealogy DNA tests used in genealogy research.

These tests are called the Y chromosome (Y-DNA), the mitochondrial DNA (mtDNA) and the Autosomal DNA tests. Here is a brief discussion of the science behind Ancestry DNA or Genealogy DNA testing.

Ancestry DNA Tests

The idea of Ancestry DNA Testing is based on the scientific fact that certain sections of an individual's DNA are passed from parent to child unchanged. The DNA of a Y chromosome is passed by a man to his sons unchanged; the mitochondrial DNA of a woman is passed to her children unchanged; and the Autosomal DNA is passed from both a man and a woman to their sons and daughters unchanged.

However sometimes there are mistakes or mutations in small sections of the DNA and so some portion of the DNA is passed from parent to child with changes or mutations. These mutations are used by genealogists for matching in Ancestry DNA.

Y Chromosome (Y-DNA) Ancestry Test

The DNA of a male's Y chromosome (Y-DNA) should be exactly the same as his father's, paternal grandfather's and the other males in this line for thousands of years – because we know that a man passes a copy of his Y chromosome unchanged to all of his sons.

However from scientific studies we know that sometimes a part or parts of the DNA will randomly mutate or change. If a son receives his father's Y-DNA with a small mutation or change then the son will pass on that mutated or changed Y-DNA to his sons who will pass on that mutated or changed Y-DNA to their sons.

These mutations or changes in the Y-DNA are used to determine the relationships among individuals and create a family tree because each mutation or change is like a branch on a tree that is slightly different from its parent.

Mitochondrial DNA (mtDNA) Ancestry Test

Both sons and daughters receive the mitochondrial DNA (mtDNA) unchanged from their mother but only the daughters can pass the mtDNA on to the next generation.

A woman's mtDNA should be exactly the same as her mother's, maternal grandmother's and the other females in this line for thousands of years.

However from scientific studies we know that sometimes a part or parts of the DNA will randomly mutate or change. If a daughter receives her mother's mtDNA with a small mutation or change then the daughter will pass on that mutated or changed mtDNA to her daughters who will pass on that mutated or changed mtDNA to their daughters.

These mutations or changes in the mtDNA are used to determine the relationships among individuals and create a family tree because each mutation or change is like a branch on a tree that is slightly different from its parent.

Autosomal DNA Ancestry Test

Autosomal DNA refers to the DNA in the "autosome" chromosomes, the non-sex chromosomes. Humans have 2 copies of 23 chromosomes (1 from the mother and 1 from the father) and one chromosome determines a person's sex - 2 Xs for female and 1 X and 1 Y for male. The other 22 are the autosome chromsomes.

The DNA in these autosome chromosomes is passed unchanged from both mother and father to the child and so 1/2 of a child's DNA should be the same as 1/2 of the mother's DNA and 1/2 should be the same as 1/2 of the father's DNA.

However from scientific studies we know that sometimes a part or parts of the DNA will randomly mutate or change. If a child receives the mother's or father's DNA with a small mutation or change then the child will pass on that mutated or changed Autosomal DNA to his or her children who will pass on that mutated or changed Autosomal DNA to the next generation.

These mutations or changes in the Autosomal DNA are used to determine the relationships among individuals and create a family tree because each mutation or change is like a branch on a tree that is slightly different from its parent.

DNA Test Results

Scientists know which sections of Y-DNA, mtDNA and Autosomal DNA have changed or mutated most often over the years and so these sections of DNA are used as the markers for DNA testing.

Based on the test results for the DNA markers an individual will be compared to individuals with similar DNA test results. The more markers 2 people have in common the closer they are as "genetic cousins".







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