Simplified DNA Terminology

More detailed definitions can be found but this is a handy simplified list I developed for a DNA class. More detailed information can be found on the ISOGG wiki.

Allele: (pronounced UH-leel) a given position, or locus (location) on a chromosome 

Ancestral: the state of a SNP that is shared by most people. After it has mutated it is called derived

Ancestry Informative Markers: Markers that give clues to geographic origins

Autosomal DNA: abbreviated atDNA or auDNA. DNA of non-sex-determining chromosomes that recombine

Base Pair: A pair of nucleotide bases on complementary DNA strands organized in a double helix

Centimorgan: abbreviated cM; a unit which is used to measure genetic distance 

Chromosome: A molecular “package” for carrying DNA in cells, organized as two double-helical DNA molecules that encode many genes

Chromosome Browser: a tool that allows you to compare one persons chromosome to another

Cross over: During re-combination each chromosome is cut at the same location, usually at one or two random spots (crossover points), and DNA segments are swapped between the two copies.

Derived: the state of a marker after it has mutated

Fully Identical: both sides of a segment match the comparison segment

Half Identical: one side (representing Mom or Dad) matches the comparison segment

Haplogroup: a genetic population group of people who share a common ancestor (mtDNA Haplogroup: maternal, mother’s line, YDNA Haplogroup: or paternal, father’s line)

Mitrochondrial DNA: Abbreviated mtDNA is outside the nucleus of the cell and EVERYONE inherit from their mother

Phasing: Separating the mother’s alleles from Dad’s so that a segment represents all of one or another.

Position or address: example Y: 3390633 FGC22501 G  A

Recombination: the exchange of DNA segments between the two copies of a chromosome (maternal and paternal) during meiosis (conception)

Segment: measured in cM a series of base pairs 

Sex Chromosomes: X and Y that determine gender 

SNP: One base pair (Single Nucletide Polymorphism) can be on the atDNA, X or Y chromosomes

STR: On the Y chromosome one position in the repeat area (Single Tandem Repeat)

Triangulation: A DNA segment match of one person matches the paper trail and DNA of two other persons (preferably with different lines of descent) that trace back to the same ancestor helping to prove they are all related both genealogically and genetically.

Copyright 2020 Kelly Wheaton. All Rights Reserved.