DNA Terminology

Adenine – is one of the four bases that make up our DNA. It is abbreviated “A.” The other bases are thymine (T), guanine (G) and cytosine (C). Adenine always pairs with thymine.


Admixture – refers to ancestry from more than one recent population group. Many people today have ancestry from more than one population and/or location.


Admixture DNA – The non-gender chromosomes that mix or recombine. Also known as autosomal DNA.


Allele –  is a genetic variant at a locus, specific location, in our genetic code; used in genetic genealogy in reference to the scientific result for a marker.


Ancestor – is someone from which you descend.


Ancestral Haplotype – In genetic genealogy, the ancestral haplotype is the set of marker values of your ancestor.


Ancestral Signature – is the oldest known or suspected haplotype for a lineage.


Ancestral State – refers to the state of a Single Nucleotide Polymorphism (SNP) that has mutated and is shared by the most people. In genetic genealogy, the ancestral state is the marker value that your ancestor had.


Autosomal DNA – also known as admixture DNA, autosomal DNA is of non-sex-determining chromosomes that mix or recombine. Humans have 22 pairs of autosomal chromosomes and a pair of sex chromosomes.


Anthrogenealogy – is the study of human origins, recent and distant, using DNA testing and genealogy.


Back Mutation – is when a marker value changes back to its original value.


Base – is a unit or building block of DNA. Adenine (A), cytosine (C), guanine, (G), and thymine (T) are the four primary bases in DNA. The order of bases is the sequence of DNA.


Base Pair – In genetics, nucleotides are called bases. A base pair (bp) is two complementary nucleotides on opposite strands of DNA.


Biogeographical Ancestry – an estimation of your ancestral proportions based on the evolutionary and geographical history of the human race.


Buccal Cell – is a type of cell found in cheek tissue inside the mouth.


Chromosome – is a structure found in the nucleus of a cell that contains genetic material. Humans have 23 pairs of chromosomes – 22 pairs of autosomal chromosome and one pair of sex chromosomes, X chromosome for female and/or Y chromosome for male.


Coding Region – is DNA which contains genes. In genetic genealogy, this most often refers to the part of the mitochondrial genome that contains genes.


CODIS – acronym for Combined DNA Index System – the FBI’s autosomal DNA database for profiles of criminal offenders.


Convergence – is the process of two genetically distant haplotypes changing over time to resemble one another.


Cytosine – is 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.


Derived State – Refers to the state of a Single Nucleotide Polymorphism (SNP) that has mutated, usually in one man, from the ancestral state and created a new haplogroup or sub-clade of a haplogroup. A positive SNP result is derived, a negative SNP result is ancestral.


Deoxyribonucleic Acid (DNA) – is the genetic code that makes each of us a unique individual. Humans inherit about one half of their genetic code from each of their parents. Our genetic code then holds the story of our heritage that has been passed down through generations.


Descendant – is someone who descends from a specific ancestor. For example, your children and grandchildren are your descendants.


DNA Amplification – is the production of many DNA copies from one or a few copies or fragments.


DNA Replication – is the process by which the DNA double helix makes a copy 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 Segment – is any continuous run or length of DNA. It is described by the locus where it starts and the locus where it stops.


DNA Sequencing – is the process of determining the exact order of the nucleotide bases in a segment of DNA.


Double Helix – is the twisted shape DNA forms when its two strands bond together. It looks like a twisting or rotating ladder.


DYS – Acronym for DNA Y-chromosome Segment – The assigned number of a marker on a segment of the Y-chromosome.


Exact Match – is when two people have exactly the same results for all markers or regions compared.


GEDCOM – Acronym for Genealogical Data Communications – is a special file format that was developed to provide a standard for encoding genealogical data. It is not used by most family tree software packages but most can import and export to GEDCOM format. Because of this, it is today used by many genealogists to exchange pedigree data files.


Genealogy – is the study of family history.


Genetic Genealogy – The latest tool for genealogists utilizing DNA to aid genealogical research. Many of these DNA terms are specific to genetic genealogy.


Genetics – is the study of genes and heredity; the study of DNA.


Genomics – the study of the complete complement of genetic material in a species.


Genome – All of the genetic material in a species. The human genome is approximately 3,300,000,000 base pairs in length.


Genotype – the genetic makeup of an individual organism.


Guanine – is 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.


Haplogroup – a group of similar haplotypes that share a common ancestor with a Single Nucleotide Polymorphism (SNP) mutation. Because a haplogroup consists of similar haplotypes, this is what makes it possible to predict a haplogroup. A SNP test confirms a haplogroup. Haplogroups are assigned letters of the alphabet, and refinements consist of additional number and letter combinations. Haplogroups pertain to your deep ancestral origins dating back thousands of years.


Haplotype – the term for the set of numbers that consists of your Y-chromosome or mitochondrial DNA results. Haplotypes are also known as signatures. Be careful not to confuse the DNA terms haplogroup and haplotype.


Heredity – is the transmission of genetic material from parents to offspring.


Heterozygous – means that two allele values at a locus are different.


Homozygous – means both allele values at a locus are identical.


HVR – acronym for Hyper Variable Region – the sections of non-coding mitochondrial DNA that are used for genealogical DNA testing.


Junk DNA – slang term usually used in referring to the non-coding region of DNA on the Y-chromosome.


Lineage – is all descendants of a specific ancestor.


Locus (pl. loci) – the name for a physical position on the genome. Can either refer to a large region such as a complete gene or a very specific region, like a particular base pair position.


Marker – A specific place on a chromosome with two or more forms, called alleles, the inheritance of which can be followed from one generation to the next. In genetic genealogy, this refers to non-coding Y-chromosome DNA. Numbers designate the individual DNA segments.


Maximum Likelihood Estimate (MLE) – the most statistically probable estimate of your ancestral proportions.


Mitochondria – a specific organelle in the cell that helps it to produce energy.


Mitochondrial DNA (mtDNA) – 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.


MRCA – acronym for Most Recent Common Ancestor – the ancestor shared most recently between two individuals.


Mutation – a heritable change in the DNA that occurs spontaneously. 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.


Non-Coding DNA – also referred to as “junk DNA,” non-coding DNA is DNA that does not contain genes. It may have other functions. All testing for genealogical purposes is done on non-coding DNA, which makes up nearly 98% of human DNA.


NRY – acronym for Non-Recombining Y – the section of the Y-chromosome that is passed from father to son on down the paternal line. While it does not recombine, it does have mutations over time.


Nuclear DNA – DNA of chromosomes found in the nucleus of the cell.


Nucleic Acids – are the basic components of our genetic code. DNA is made up of four types of nucleic acids: adenine (A), cytosine (C), guanine (G), and thymine (T).


Nucleus – the membrane-bound organelle containing the chromosomes.


Null – A null is a value of zero on a marker. Nulls can occur due to missing genetic material on a marker, or a Single Nucleotide Polymorphism (SNP) can sometimes cause a null result. Several YSTR markers have been identified in certain families to have null results.


Organelle – A cell structure with specialized functions.


Outbreed – is when an individual’s parents’ common ancestry was more than ten generations in the past.


Palindrome – A double-stranded DNA segment in which the sequence of one strand is in the reverse order to the other strand.


Parallel Mutation – is when the same genetic change happens in completely unrelated lineages.


Pherogram – for Short Tandem Repeats (STR)s, a plot which shows the length of a fragment of DNA. This allows its allele value to be measured.


Phylogenetics – is the study of how genetics can be used to show how people are related.


Phylogenetic Tree – is the reconstruction through genetics of a lineage.


Polymorphism – the property of having more than one state or alternate sequence at a particular position. The alternate states are called alleles.


RecLOH – Acronym for Recombinant Loss of Heterozygosity – is a process by which one copy of genetic code is copied over others. The result is identical values. In genetic genealogy, this is most significant for the Y-chromosome.


Palindromic STR (short tandem repeat) – markers may be copied over each other.


Recombination – is the mixing of the DNA on each chromosome that you receive from your mother and father. Different chromosomes and different parts of each chromosome are more or less likely to recombine in a single generation.


Sex Chromosome – The X- or Y-chromosome. Normally males have one X and one Y and females have two X.


SNP – acronym for Single Nucleotide Polymorphism. A SNP test confirms your haplogroup by determining if a SNP has mutated from its derived or ancestral state. A SNP is usually found on a different area of the Y-chromosome than where the YSTR markers are. Sometimes, a SNP may cause a null result on a marker.


STR – acronym for Short Tandem Repeat – a short DNA motif (pattern) repeated in tandem.


Subclade – is a minor branch of the human genetic trees. This may be either the Y-chromosome tree or the mitochondrial tree. Subclades are more specific to a location or population group than the major branches (haplogroups).


Telomere – is the end of a DNA chromosome. Each of our autosomal and sex chromosomes has two telomeres.


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.


Triangulation – a method of determining the DNA haplotype of an ancestor using the DNA results of direct line descendants.


X-chromosome – the female sex chromosome, if a child receives one X from the father and one X from the mother, the child’s gender is female.


Y-chromosome – the male sex chromosome. In other words, only males have a Y-chromosome, which they receive from their father, who received it from his father, and so on. This transmission of the Y-chromosome down the male line is why it is useful for surname testing to determine if two males share a common ancestor.


YSTR – acronym for Y-chromosome Short Tandem Repeat. The number of times the sequence of bases repeat that determines the value of the marker.



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Lena Butler

My name is Lena Butler. I live in San Diego, California. I work as a customer service representative for TestCountry.com. I attended the University of San Diego and majored in marketing. I enjoy spending time at home, working on my painting and playing with my two pet rabbits, Carl and Lenny, when I am not here sharing interesting posts :)

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