DNA Glossary

A list of the nomenclature used in genealogical DNA testing

Last Revised:  October 28 , 2009

Allele --- Variations at a particular site on a chromesome expressed by a number representing the frequency of occurance.(Pronounced all-eel).

Cell --- A body building block, each containing a complete sample of our DNA.

Chromosome --- A tightly folded bundle of DNA. A chromosome contains sequences of repeating nucleotides known as STRs

Convergence --- The coincidence of two different haplotypes' having the same mutations to appear similar.

CR --- Coding Region (00575 to 16000) of mitochondrial DNA.

CRS --- Cambridge Reference Sequence - the standard mtDNA genome.

DNA --- Molecules made up of four chemical bases: Adenine (A), Cytosine (C), Thymine (T) and Guanine (G) combined into pairs, A with T and C with G, to make the "rungs" of the DNA ladder. The exact order of the pairs is called the DNA sequence, i.e., the genetic code.

DYS --- DNA Y-chromosome Segment. A STR on the Y chromosome is designated by a DYS number.

DYS Marker --- The marker indicated by the DYS number.

Gene --- Sections or segments of DNA that form the individual units of heredity.

Haplogroup --- Large groups of haplotypes that can be used to define genetic populations (often geographically oriented).

Haplotype --- The numbered results of a genealogical Y-DNA test.

HVR1 --- Hyper-Variable Region 1 (16001-16569)

HVR2 --- Hyper-Variable Region 2 (00001-00574

MRCA --- Most Recent Common Ancestor

Mitochondrial DNA (mtDNA) --- is contained in the cytoplasm of the cell, rather than the nucleus. It is passed by the mother to both male and female offspring without any mixing, so your mtDNA is the same as your mother's mtDNA, which is the same as her mother's mtDNA, etc.

Null --- A value of zero on a marker. It can occur due to missing genetic material on a marker, or a SNP can sometimes cause a null result.

PCR --- Polymerase Chain Reaction.

STR --- Short Tandem Repeat. Rate of change is about one every twenty generations.

STR Marker --- A segment of DNA with known genetic characteristics.

SNP --- Single Nucleotide Polymorphisms - locations on the DNA where one nucleotide has "mutated" or "switched" to a different nucleotide. They are named with a letter code and a number based on discovery. Rate of change is about one every few thousand years.

SNP Marker --- A single nucleotide with a known genetic characteristic.

Subclade or sub-clade --- a branch of the haplogroup. Deepclade is a far branch.

Y Chromeosome DNA (Y-DNA) --- The DNA of the Y chromeosome in males. Females do not have a Y chromeosome.

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