Family Tree DNA Glossary
A
Aboriginal
Relating to a group of people indigenous to a geographic region; the original inhabitants of a region.
Adenine
The "A" of the four bases that make up DNA. The other bases are thymine (T), guanine (G) and cytosine (C). Adenine always pairs with thymine.
Admixture
Of mixed ancestry or mixed origins.
Allele
A DNA sequence that repeats at a certain locus or place. The allele value is the number of times the sequence repeats. Pronounced uh-LEEL.
Amplification
See DNA amplification.
Ancestral signature
The oldest known or hypothesized haplotype for a particular lineage.
See also: modal haplotype
Anthrogenealogy
The study of human origins, recent and distant, using DNA testing and genealogical methods.
Anthropology
The study of humans, particularly in terms of origin and culture.
Atlantic Modal Haplotype (AMH)
See Western Atlantic Modal Haplotype
Autosomal DNA
The non-sex chromosomes. Humans have 23 pairs of chromosomes: the first 22 pairs are autosomal DNA and the 23rd pair consists of the sex chromosomes (the X- and Y- chromosomes).
B
Base
The unit or building block of DNA. Adenine (A), cytosine (C), guanine, (G), and thymine (T) are the four bases in DNA. The order of bases is the sequence of DNA.
Base pair
Two bases bonded together and attached to one of the strands in the DNA double helix. Adenine always pairs with thymine, and guanine always pairs with cytosine.
Buccal cell
A type of cell found in cheek tissue inside the mouth.
C
Cambridge Reference Sequence (CRS)
The mitochondrial DNA first sequenced in 1981 which is used as a basis for comparison with mtDNA test results.
Catalyst
A substance which starts or speeds up a chemical reaction without being affected by that reaction.
Chromosome
A structure found in the nucleus of a cell that contains genetic material. Humans
have 23 pairs of chromosomes; 22 pairs of autosomes and one pair of sex chromosomes.
Coding region
A region of DNA which contains genes.
Cohanim Modal Haplotype
The Y-DNA haplotype most commonly found among males with an oral tradition of Cohen ancestry.
Cohen
The Hebrew word for priest which refers to a direct male descendant of Aaron, the brother of Moses; plural: Cohanim.
Combined DNA Index System (CODIS)
The CODIS system uses marker locations in the autosomal DNA. CODIS test results are maintained in an FBI database which is used to identify people and solve crimes.
Complementary sequences
Opposing strands of DNA which bond together to form the double helix. The bases always complement one another with adenine and thymine pairing together and cytosine and guanine pairing together.
Convergence
The process of two unrelated or less related lineages changing over time to resemble one another.
Cross-over
See recombination
Cytosine
The "C" of the four bases that make up DNA. The other bases are adenine (A), guanine (G), and thymine (T). Cytosine always pairs with guanine.
D
Deoxyribonucleic acid (DNA)
A chemical consisting of a sequence of hundreds of millions of nucleotides found in the nuclei of cells. It contains the genetic information about an individual and is shaped like a double-stranded helix.
DNA amplification
The production of many DNA copies from one or a few copies or fragments.
DNA replication
The process by which the DNA double helix makes a copy of itself or of a fragment of itself. It uses the old DNA as a template for the synthesis of new DNA strands. In humans, replication occurs in the cell nucleus.
DNA sequencing
The process of determining the exact order of the nucleotide bases in a segment of DNA.
Double helix
The twisted shape DNA forms when its two strands bond together. A double helix looks like a twisting or rotating ladder.
DNA Y-chromosome Segment (DYS)
The "name" of a marker on the Y-chromosome. It is assigned based on a nomenclature system controlled by the HUGO Gene Nomenclature Committee, which assigns DYS numbers to newly discovered markers.
E
Enzyme
A protein that facilitates a specific chemical reaction by working as a catalyst.
Exact match
Two individuals with exactly the same results for all markers or regions compared.
F
Family Tree DNA Time Predictor (FTDNATiPTM)
A program used to calculate estimates of Time to the Most Recent Common Ancestor (TMRCA). It is the world's first calculator that incorporates mutation rates specific to each marker. This greatly increases the power and precision of estimates.
G
Gene
A segment of DNA which contains the genetic code to make a certain protein or part of a protein.
Genealogical Data Communication (GEDCOM)
A type of file format used by genealogical software to make your family tree. You can upload your GEDCOM file to your Family Tree DNA personal page as well as Ysearch or mitosearch. Learn more about GEDCOM here
Genealogy
The study of family history.
Generation
The number of years between the birth of the parents and the birth of their children. Different studies use different numbers of years per generation. At Family Tree DNA we use 25 years.
Genetic cousins
Individuals whose Y-DNA or mtDNA test results match one another.
Genetic distance
The number of differences, or mutations, between two sets of results. A genetic distance of zero means there are no differences in the results being compared against one another (exact match).
Genetics
The study of genes and heredity; the study of DNA.
Genome
The entire complement of genetic material in a chromosome set. The human genome is composed of 46 chromosomes, with a total of 3 billion base pairs.
Genotype
The genetic makeup of an individual organism.
Glacial maximum
The scientific term for the peak of an ice age.
Guanine
The "G" of the four bases that make up DNA. The other bases are adenine (A), cytosine (C), and thymine (T). Guanine always pairs with cytosine.
H
Haplogroup
A genetic population group associated with early human migrations and which can today be associated with a geographic region. It is important to note that even though female and male haplogroups may have the same letters, their definitions are different.
Haplotype
One person's set of values for the markers that have been tested. Two individuals that match exactly on all markers have the same haplotype.
Heredity
The transmission of genetic material from parents to offspring.
Human Genome Organization (HUGO)
The entity to which, among other things, scientists submit new markers for DYS number assignment.
Hypervariable Region (HVR)
One of two regions commonly used in mitochondrial DNA tests which does not code for any known function.
J
Junk DNA
Stretches of DNA that do not code for genes, also called non-coding DNA. Most of the genome consists of non-coding DNA, and was therefore long thought to be 'junk.' Scientists have found that in addition to containing markers that are helpful for genetic genealogy, parts of these non-coding regions have regulatory and other functions.
L
Loci
The plural of locus, or marker. Locus and loci are Latin words for location(s).
M
Marker
A physical location (locus) on the chromosome. Family Tree DNA offers 3 levels of Y-DNA testing: 12-marker, 25-marker and 37-marker.
Meiosis
The stage in which sperm and egg cells are formed. It is during this process that the autosomal chromosomes recombine and mutations occur.
Microsatellite
See short tandem repeat.
Mitochondria
A specific organelle in the cell that helps it to produce energy.
Mitochondrial DNA (mtDNA)
The genetic material found in mitochondria. It is passed down from females to both sons and daughters, but sons do not pass down their mother's mtDNA to their children.
Modal haplotype
The most common result for each marker tested in a group of results.
See also: ancestral signature.
Most Recent Common Ancestor (MRCA)
The ancestor shared most recently between two individuals.
Mutation
A heritable change that occurs in genetic material. It may lead to a different number of repeats of a certain sequence or a change in one of the bases in a sequence.
Mutation rate
The frequency with which random mutations occur.
N
Nucleotide
A piece of DNA that contains one base, one phosphate group, and one sugar unit. Thousands of nucleotides joined in sequence make a molecule of DNA.
Nucleus
The membrane-bound organelle containing the chromosomes.
P
Pherogram
For STRs, a plot which shows the length of a fragment of DNA. This allows its allele value to be measured.
Phylogenetic tree
See Y-DNA phylogenetic tree.
Polymerase
The enzyme that starts the process of making nucleic acids or assembling RNA or DNA.
Polymerase Chain Reaction (PCR)
A technique allowing the production of multiple copies of extremely small amounts of DNA fragments using DNA polymerase and specific primers.
Polymorphism
See mutation.
Primer
A short DNA sequence used in the polymerase chain reaction to initiate DNA synthesis at a particular location.
Protein
The main building block of our cells. Each one has a specific function.
R
Recombination
An event occurring during meiosis - the formation of sperm and egg cells. One chromosome from the mother and the other from the father break and trade segments with one another.
Replication
See DNA replication.
Restriction enzyme
A protein that recognizes a certain sequence of DNA and cuts the DNA at that site.
Restriction Fragment Length Polymorphism (RFLP)
See single nucleotide polymorphism.
S
Sequencing
See DNA sequencing.
Sex chromosome
The X- or Y-chromosome. Normally males have one X and one Y and females have two Xs.
Short Tandem Repeat (STR)
A short DNA motif (pattern) repeated in tandem. ATGC repeated eleven times would give the marker a value or allele of 11.
Single Nucleotide Polymorphism (SNP)
A change in the DNA that happens when a single nucleotide (A, T, G, or C) in the genome sequence is altered. A person has many SNPs that together create a unique DNA pattern for that individual.
Surname
A last name or family name traditionally passed down from father to son.
T
Thymine
The "T" of the four bases that make up DNA. The other bases are adenine (A), cytosine (C), and guanine (G). Thymine always pairs with adenine.
Time to the Most Recent Common Ancestor (TMRCA)
The amount of time or number of generations since individuals have shared a common ancestor. Since mutations occur at random, the estimate of the TMRCA is not an exact number (i.e., 7 generations), but rather a probability distribution. As more information is compared, the TMRCA estimate becomes more refined.
Transmission event
The passage of genetic material from one generation to the next.
U
Unique Event Polymorphism (UEP)
See single nucleotide polymorphism.
W
Western Atlantic Modal Haplotype (WAMH)
The most common Y-DNA haplotypes found in Europe’s most common Y-DNA haplogroup, R1b.
X
X-chromosome
One of the two sex chromosomes, X and Y. X is the sex chromosome that is present in both sexes: singly in males and doubly in females.
Y
Y-chromosome
One of the two sex chromosomes, X and Y. The Y-chromosome passes down from father to son. Females do not receive it. The fact that the Y-chromosome goes down the paternal line makes it valuable for genealogy studies, since it typically follows a surname line.
Y-DNA phylogenetic tree
A graphic representation of the Y-DNA haplogroups according to the YCC classification. Haplogroup names and major clades are labeled and mutation names are given along the branches of the trees.
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