By now the poor brain should be spinning around the terms that are used to communicate information about DNA. This is especially true when ordering a DNA test, and the results are given in a bunch of different terms. Having some idea how all these terms fit together is a helpful thing. My own DNA testing results state:
"We provide the actual scientific Allele values and DYS #'s for your results unless the markers were discovered at the University...."
My results were given as "Panel 1 (1-12)", "Panel 2 (13-25)", and "Panel 3 (26-37). Under each panel the results were given as "Locus", "DYS#", and "Alleles". Wow! Terms, terms, and more terms...what is one to do?
To begin, a "Panel" is how the DNA testing is organized and actually carried out in a testing laboratory. Panel 1 is the first group of 12 genetic markers that have been accepted as the standard among all testing labs. The "Locus" is the assigned panel number that each marker has received beginning with number 1 to number 12 for Panel 1.[number 13-25 for Panel 2, and number 26-37 for panel 3] Each "Locus" number corresponds to a DYS# and Allele value. The DYS# and Allele values had already been described in separate research labs which would of course cause a great deal more confusion if each lab reported their results under different labels!
Now the term DYS# is an abbreviation for D = DNA, Y = Y-Chromosome, and S = (unique) Segment.
A unique segment is the part of the DNA molecule [in this case the Y-chromosome] that has undergone changes (mutation) among several nucleotides in a row. Remember that a change at only one nucleotide is called a SNPs (single nucleotide polymorphism). Changes that have occurred at more than one site in a row (segment) have been termed a "Short Tandem Repeat" or STR. These short, tandem (next to one another) repeats are identified along the DNA molecule at the address called "Allele Value". [The allele was the earliest concept of genetic addresses for the codons that produced a protein.]
Here is the key issue and perhaps the most confusing. A single nucleotide change (SNP) is a very rare occurrence. This change (SNP) is past down generation to generation among a family, thus an ethic group. The SNP is used to characterize a "Haplogroup". The STR (Short Tandem Repeat) happens all along the DNA molecule, and when analyzed together produce the genetic finger print that is called the "Haplotype". Haplogroup (SNP) - Haplotype (STR). Using the Y-chromosome, the haplotype should be the same or very close to all males in the family. It is the STRs that are used to match our ancestors. More to come.