Can anyone tell me what the markers mean? Each one has a value, but what is the orginal meaning of the marker, does it, in itself mean anything that we can understand? When you say "mutations", do you mean that it is just a different value than the rest of the group has? Isn't there anything significant about that particular mutation at that particular marker? Kelly

Hi Kelly, The following is something I put together a few years ago for my DNA web page. Perhaps this will help with the basics a bit. Everyone of us contain structures called chromosomes. These chromosomes usually come in pairs, one inherited from the mother and one from the father, and humans have 23 pairs of chromosomes altogether. In 22 of the 23 pairs, the 2 chromosomes are very similar. However, the 23rd pair is made up of two possible combinations of 2 very different chromosomes, the X and the Y chromosomes. All of us have at least one X chromosome, which we have inherited from our mother. The second chromosome in this pair is always inherited from the father. If it is another X chomosome then the pair readily mixes and the embryo developes into a female. If the second chromosome inherited from the father is a Y chromosome then the embryo developes into a male. Since a male's 23rd pair are disimilar (X & Y), genetic material cannot readily exchange between them. The result is that the Y chromosome of every living man contains portions that directly resembles that of his father, grandfather, great grandfather etc. and cousins of any degree who also have the same male ancestor. The Y chromosone is about 60,000,000 base pairs long. One base on the DNA strand can be one of the following four nitrogen containing chemicals: A (adenine), T (thymine), C (cytosine) and G (guanine). There are two strands in the DNA chain parallel to each other and connected. They are connected because Adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). Thus, if you have a A on one strand then its opposite strand will have a T so they can join. When the DNA within the male Y chromosome is copied from generation to generation, small mistakes are occasionally made. These mistakes give rise to differences between Y chromosomes of two individuals called "polymorphisms". An person's combination of polymorphisms identifies a unique sequence or "haplotype" with which to make comparisons to that of another individual. STRs (abbreviation for Short Tandem Repeats) are sections of DNA where a short pattern (2-5 bases) has been identified as repeating a certain number of times in a row (in tandem). DYS391 is an identified STR with the 'GATA' pattern repeating at one specific location (repeating patterns at specific points are called markers). For many Kincaids in our project it has been determined that the DYS391 marker repeated 12 times. In that section of the Y-DNA one strand of the DNA looks like: GATAGATAGATAGATAGATAGATAGATAGATAGATAGATAGATAGATA. For other Kincaids in the project there was a mutation in one of the GATA pairs (ie. perhaps a G became a C) resulting in only 11 GATA repeats being counted for the same marker instead of 12 (ie. a mutation is when the number of repeats increases or decreases by one or occasionally two or more). Since we are dealing with more than one base pair (ie. one letter) then mutations can be observed frequently enough in STR markers to be of use for genealogy. Peter A. Kincaid Fredericton, NB, Canada ----- Original Message ----- From: lewisjo@junct.com To: KINCAID@rootsweb.com Sent: Friday, October 17, 2008 3:28 PM Subject: [KINCAID] DNA Question Can anyone tell me what the markers mean? Each one has a value, but what is the orginal meaning of the marker, does it, in itself mean anything that we can understand? When you say "mutations", do you mean that it is just a different value than the rest of the group has? Isn't there anything significant about that particular mutation at that particular marker? Kelly