Simplistic Scientific Overview:
The diversity seen in our genetic inheritance is the result of receiving half of our genes from our father and half from our mother. Every physical trait we possess was passed down from our ancestors through DNA. DNA serves as a blueprint (in code) for every physical and biological part and function of every life form.
Every cell in the human body (except reproductive cells) contains an identical set of 46 chromosomes (23 pairs). Each chromosome is one giant molecule of double-stranded DNA.
A gene is the smallest element of hereditary material. It is a small portion of a chromosome. There are over two million genes contained in the 46 human chromosomes. Many human genes are identical from person to person. Those that are different determine eye color, blood type, etc.
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The pair of chromosomes that determine sex are the X and Y chromosomes. Women always have a pair of XX chromosomes and men always have a pair that is XY. If you are male, then your Y-chromosome is identical to your father's Y-chromosome and your X-chromosome is identical to one of your mother's. (If you are a female, then one of your X-chromosomes came from your mother and the other X-chromosome from your father. There is no pattern regarding which X-chromosome you will pass on to your children.)
Male Y-Chromosome DNA Tests:
Y-DNA 12 Marker Test is the world standard to verify the Y chromosome for gene matches between males. When 2 men show the same identical results, then it is proof that they are descended from a common male ancestor in their paternal line.
A perfect match of 25 markers between men's Y-chromosomes means a lesser number of generations to their most common recent ancestor.
Over time, subtle mutations may occur on the Y-chromosome. As one's paternal line is extended generationally, there is a greater chance that a change in a particular gene will occur (as is evident in the tables below).
Specific COWAN findings (as of 13 October 2003):
