Genetics Glossary

Adenine – One of the four bases of DNA; A

Allele – A Particular structure or sequence of DNA at a specific portion or position on the DNA molecule.

Amino Acid – One of 20 types of small molecules that form proteins. Three DNA bases code for each of the amino acids.

Autosome –  All of the chromosomes other than the two sex chromosomes; humans have 23 pairs or 44 autosomes.

Base – The building blocks of DNA that are the genetic code. they are A (adenine), T (thymine), G (guanine) and C (cystosine).

Base Pairs – Complimentary parts of DNA that bind together, adenine to thymine and guanine to cytosine.

Bp – Base Pair

Cambridge Reference Sequence – (CRS) the sequence of bases in mtDNA when it was originally sequenced and that is used as the standard for interpreting mtDNA genealogy tests. Individual mtDNA testing reports outline where there is a difference in tested sample and this reference sample. On a large scale, it used to type mtDNA for studies of human evolution, population genetics, and mitochondrial diseases. The original CRS was published in 1981 and revised in 1999. Cambridge University.

Cell – Control unit of life,; generally has a nucleus with chromosomes and their DNA and cytoplasm with mitochondria containing mtDNA.

CR – Control region, also called hypervariable region (HVR) because the majority of mtDNA mutations occur in that segment.

Cytoplasm – The material within the cell but outside of the nucelus.

Cytosine – One of the four bases of DNA; C

Dexoxyribone Nucleic Acid – DNA

DNA – Dexoxyriboncleic acid. The molecule whose sequence of bases (forms the genetic code). A coiled double-stranded molecule resembling a ladder where the “rungs” consist of 4 different paired bases, A to T, and G to C. A = adenine; T = thymine; G = guanine; C = cytosine.

Double Helix – The structure of DNA that looks like a coiled ladder or spiral staircase.

DYS – D = DNA; Y = Y-chromosome; S = segment. used to name a specific location or “marker” on the Y-chromosome. DYS numbers are assigned in the order in which they are discovered. Markers on a chromosome, for instance chromosome 3, would be label D3S. The DYS numbering scheme standards are set by HUBO, the Human Gene Nomenclature Committee of London, England.

Gene – A specific portion of the DNA sequence that is the basic unit of heredity. A sequence of DNA bases that code for a specific protein. Alternate forms of a gene called alleles.

Genome – The total and complete genetic material of an organism, the complete DNA sequence of an organism, including all of the DNA found within the chromosomes and mitochondria. when discussing mtDNA alone, it can be referred to as the mtDNA genome.

Guanine – One of the bases of DNA; G

Haplogroup – A family of Haplotypes. A haplogroups is a group of similar haplotypes that share a common ancestor, paternal (Y chromosome) or maternal (mtDNA), having the same SNP’s in common.

Haplotypes – A series of known DNA sequences, specific alleles, or markers, on a chromosome. It can be a DNA sequence inherited unchanged from father to son in the Y-chromosome or pattern inherited from mother to child in the miochandrial DNA.

HVR – Hypervariable Region. There are two: HVR1 approximately covering 16001 to 16569 and HVR2 covering 00001-00574 numbered mtDNA bases. The areas do not contain genes and have a faster mutation rate than the remainder of the mtDNA.

Karyotype – A chart of chromosomes arranged by size.

Marker – A specific and identifiable portion of the  DNA moilecule.

Meiosis – The specialized form of division that results in sperm and eggs with half the number of chromosomes.

Microsatellite – A short DNA sequence that repeats also known as STR.

Mitochondria – Small ovoid-shape structures in the cytoplasm of the cell that produces energy and contains their own DNA, known as mtDNA.

Mitosis – Cell division to produce two daughter cells, each containing the same number of original chromosomes.

mtDNA – Mitochondrial DNA, mtDNA is inherited  from the mother by both her sons and daughters, but only her daughter can pass it on to the next generation.

Non-paternity event – A supposed father and son are found not to be biologically related.

NRY -Nonrecombining region of the Y chromosome used in testing for genetic genealogy.

Nucleotide – One of the 4 bases (A, T, C, G) of DNA along with structural phosphate and sugar molecules.

Nucleus – A structure within a cell that contains chromosomes.

Organelle – A structure within a cell such as a single.

Polymorphic – Many shapes

Protein – A large molecule consisting of chains of small molecules, the amino acids. The sequence of amino acids is determine by the genetic code.

Pseudoanutosomal Region – An area om the Y-DNA that may swap genetic information with its partner X chromosome. This area is not used for testing.

Sex Chromosome – A chromosome that determines sex; human males have two: an X and a Y; human females have two X chromosomes. the remaining 2 pairs of chromosomes are autosomes.

SNP – Single Nucleotide Polymorphism. A change in one base, for instance a thymine (T) changes to a cytosine (C). SNPs change (mutate) more slowly than STR’s (mitcrosatellites).

STR – Short tandem repeats or microsatellites; repeated sequnces of from 2 to 5 base pairs, and can be repeated many times. Changes(mutations) occur more freguently than SNP’s and the number of repeats found at a given marker may increase or decrease.

Thymine – One of the four bases of DNA;  (T).