Glossary

 

allele

 

At many positions on the human genome, multiple variations are known to exist. The set of variations at any particular position are known as alleles. Genealogical DNA tests identify many alleles, and enable these to be used to infer relationships.

 

atDNA

 

An abbreviation for autosomal DNA

 

autosome

 

The autosomes are the non-sex chromosones. Humans automsomes are numbered from 1 to 22. Autosomal DNA tests use the genetic material in these chromosones.

 

base pairs

 

A base pair represents a single rung on the DNA ladder. The specific value of a base pair at a particular genomic position can be represented by a single letter: A, T, G, C. Base pair is sometimes abbreviated to bp.

 

clade

 

Another term for a haplogroup. (See the entry for haplogroup for more information.)

 

crossover

 

The recombined chromosones passed by a parent to a child are formed by stitching together sections of the parent's two copies of that chromosone. Crossover points are the end positions of the sections.

 

genome

 

The genome is the complete set of the DNA (genetic information) for an individual of a species.

 

haplogroup

 

A haplogroup is a group of people which share a common ancient patrilineal or matrilineal ancestor as determined by Y-DNA or mtDNA respectively. Major haplogroups are identified with a single letter. Sub divisions of haplogroups are named by adding a number or letter (with the letters and numbers alternating for successive divisions). Genealogical testing has led to a massive increase in the number of haplogroups and smaller haplogroups are typically now identified by a characteristic SNP.

 

matriline

 

The lineage purely back through the maternal line (i.e. an individual's mother, mother's mother, mother's mother's mother and so on). mtDNA is passed down this ancestral line with minimal changes.

 

meiosis

 

Meiosis is a key genetic stage in the reproductive process which incorporates the recombination of one parent's chromosones to produce a single set which are passed to the child.

 

MRCA

 

An acronym for Most Recent Common Ancestor.

 

mtDNA

 

An abbreviation for michrochondrial DNA

 

patriline

 

The lineage purely back through the paternal line (i.e. an individual's father, father's father, father's father's father and so on). Y-DNA is passed down this ancestral line with minimal changes.

 

recombination

 

Recombination is the generic process by which sections of a pair of two chromosones are stitched together to create a single chromosone. Each parent provides a single recombined chromosone of each type to their child.

 

TMRCA

 

An acronym for Time to Most Recent Common Ancestor.

 

short tandem repeats

 

These occurs when a short sequence of base pairs are repeated, and the repeats are adjacent.

 

SNP

 

An abbreviation for single nucleotide polymorphism. This is a variation to a inherited DNA at a single nucleotide (base).

 

subclade

 

A subdivision of a clade. Informally a subclade is a (minor) haplogroup.

 

XDNA

 

An abbreviation for X chromosone DNA. This is a sex chromosone. Children receive an X chromosone from their mother, and females additionally receive an X chromosone from their father.

 

YDNA

 

An abbreviation for Y chromosone DNA. This is the male sex chromosone and is inherited by a male from his father.