If you are new to DNA testing for genealogy, you probably wonder why only males can be tested for this project. The chart and explanation below show how the sex of a child is determined by the presence or absence of a Y chromosome. We are fortunate that the sex chromosomes are different from the other 22 pairs of chromosomes. The Y and X chromosomes are so different that they do not exchange genetic material (DNA). The Y chromosome is passed from father to son only and contains no DNA from the mother. These properties allow us to use the Y chromosome to track the male line only, making it a very powerful tool for genealogy.

    The chart below shows two lines that descend from a common ancestor, James PARKER.  Each son, John 1767 and Thomas 1769, received a copy of the Y-chromosome of their father James. If we could test brothers John and Thomas, we would expect them to match exactly on their Y-DNA. The same condition holds for each succeeding generation. However, the only living males to test are 4th cousins Elijah, born 1915, and Robert, born 1924. Each of these men are 5 generations from their common ancestor James. The names have been changed, but we have actual data for a genealogy like this in which Elijah 1915, and Robert 1924, have an exact match on their Y-DNA. The matching Y-DNA of Elijah and Robert tells us that they both descend from the same ancestor. Traditional genealogy research identified that ancestor as James PARKER, born 1734 in Pennsylvania.

---

---

HOME       FAQ        LINKS        RESULTS       ANCESTORS        MATCHES & NON-MATCHES

---