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vocabulary

adenine
admixture mapping or mapping
allele
Ancestry Informative Marker (AIM)
antecedent
anthropology
autosome
base
base-pair
base sequence
biogeography
chromosome
clades
complementary sequences
cytosine
demography
DNA
DYS
double helix
enzyme
ethnic
exogamous
endogamous
gene
genetic genealogy
genetics
genome
genome projects
guanine
haplotype
haplotype diversity
haplogroup
heredity
heterogeneous
homogeneous
junk DNA
locus (pl. loci)
marker
microsatellite
mitochondrial DNA
MRCA
mtDNA
multiplexing
mutation
mutation rate
nucleic acid
nucleotide
nucleus
PCR
pharmacogenomics
polarized
polymorphism
population
restriction enzyme
sequencing
sex chromosomes
Single Nucleotide Polymorphism (SNP; pronounced snip)
STR marker
thymine
transmission event
Y-chromosome
adenine

 Designated by the letter A, it is a purine base. One of the four base molecules present in DNA.

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admixture mapping or mapping

 A method of screening the human genome that relies on a quantification of population structure within as well as between individuals. We call DNAPrint’s platform of proprietary genomic maps and algorithms ADMIXMAP.

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allele

 One of several forms of a gene that can exist at a single location (marker) on a chromosome. When STR's are measured on the Y-chromosome, this corresponds to a different number of repeat units. For example, for DYS19 where TAGA is the repeat unit, different alleles could be 13, 14, 15 repeats of the TAGA unit etc.

A father will pass his Y-chromosome on to his son and thus the son will inherit the same alleles (i.e. no. of repeat units).

Alleles will be changed if miscopied, resulting in a mutation. Some alleles are more common in particular populations

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Ancestry Informative Marker (AIM)

 AIMs are the subset of genetic markers that are different in allele frequencies across the populations of the world. Most polymorphism is shared among all populations and for most loci the most common allele is the same in each population. An ancestry informative marker is a unique set of genetic markers that occurs mostly in particular founder population sets but may also be found in varying levels across all or some of the populations found in different parts of the world.

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antecedent

 A preceding event, condition, or cause. The conditional element in a proposition.Used herein to denote individuals that came before.

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anthropology

 The science of human beings; especially : the study of human beings in relation to distribution, origin, classification, and relationship of groups or clades or families, physical character, environmental and social relations, and culture.

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autosome

 A chromosome not involved in sex determination. The human genome consists of 46 chromosomes, 22 pairs of autosomes (numbered 1-22), and one pair of sex chromosomes (the X and Y chromosomes).

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base

 In DNA, this can be either adenine (A), cytosine (C), guanine (G) or thymine (T). They are derived from either purine or pyrimidine.

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base-pair

 Two complementary bases joined by hydrogen bonds usually as part of the DNA molecule; base-pairing occurs between (purines and pyrimidines) i.e. between A and T and between G and C.

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base sequence

 The order of nucleotide bases in a DNA molecule e.g AGTACGTA etc.

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biogeography

 A science that deals with the geographical distribution of animals and plants.

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chromosome

 The structure by which hereditary information is physically transmitted from one generation to the next. Humans have a total of 46, found in the nucleus of each cell.Each chromosome is formed when the DNA strand combines with lots of small proteins called histones. The DNA and histones automatically wrap themselves up into a shape that looks like an elongated letter X.

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clades

 An anthropology term used to describe a group of individuals, families, tribes or sub set populations that have originated from a foundation population and have branched out. The four major clades are sub Saharan African, Native American, Indo European and East Asian.

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complementary sequences

 DNA is made up of two long strands connected together along the middle (a bit like a zip), where bases on one strand are bonded to bases on the other side.

If the base sequence is G-T-A-C on one side, the other side is always C-A-T-G, thus complementing each other.

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cytosine

 Designated by the letter C, it is a pyrimidine base. One of the four base molecules present in DNA.

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demography

 The statistical study of human populations especially with reference to size and density, distribution, and vital statistics.

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DNA

 DeoxyRibonucleic Acid. The genetic material of organisms, usually double-stranded; a class of nucleic acids identified by the presence of phosphate, deoxyribose (a sugar), and the four bases. Often forms the familiar double-helix. Within DNA are the code-words needed to form proteins, although much of the DNA is termed 'junk DNA' and has no known function.

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DYS

 D = DNA: Y = Chromosome; S = Single copy sequence. The DYS numbering scheme (e.g. DYS388, DYS390) for the Y-STR haplotype markers are controlled and administered by an international standards body called HUGO - Human Gene Nomenclature Committee - based at University College, London.

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double helix

 The familiar shape that two linear strands of DNA with complementary sequences assume when bonded together.

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enzyme

 A protein that can speed up a specific chemical reaction without being changed or consumed in the process.

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ethnic

 Of or relating to large groups of people classed according to common racial, national, tribal, religious, linguistic, or cultural origin or background.

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exogamous

 Marriage outside of a specific group especially as required by custom or law. Meant herein to refer to admixture from outside of a group.

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endogamous

 Marriage inside of a specific group especially as required by custom or law. Meant herein to refer to admixture from inside a group.

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gene

 The basic unit of heredity; a sequence of DNA nucleotides on a chromosome.

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genetic genealogy

 The new field of family history research utilising the Y-chromosome and mtDNA to prove or disprove biological connections. The Y-chromosome links the strictly paternal line (father to son), whilst mtDNA links the mother to offspring line (mother to sons and daughters).

For the vast majority of family history studies, the Y-chromosome is studied.

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genetics

 The study of the patterns of inheritance of specific traits.

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genome

 All the genetic material in the chromosomes of a particular organism; its size is generally given as the total number of base-pairs. In humans, 46 chromosomes make up the genome, with a total of 3 billion bases pairs of approx. 2 metres in length packaged into a tiny nucleus.

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genome projects

 Research and technology development efforts aimed at mapping and sequencing some or all of the genome of an organism. The improvements and lower cost of technology that genome projects have brought make possible the new field of genetic genealogy for genealogists.

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guanine

 Designated by the letter G, it is a purine base. One of the four base molecules present in DNA.

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haplotype

 Your Y-DNA haplotype is a set of 21 numbers (if using 21 STR markers), each number representing your allele at a given STR marker. Two or more haplotypes may be compared as a check for a genetic relationship.

There are many haplotypes to be found from many different populations around the globe at www.yhrd.org that may be used to compare haplotypes. Also, the Ybase database can accept genealogical as well as haplotype data.

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haplotype diversity

 A measure of the uniqueness of a particular haplotype in a given population.

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haplogroup

 Haplogroups are large groups that can be used to define genetic populations and are often geographically orientated. For example, when the Y-chromosome is tested, many males who live along the western coasts of Europe belong to Haplogroup R1b (used to be called HG1), which belies the historical movement of males along that coast.

The Y-chromosome haplogroup of an individual is not defined by their haplotype (because haplotypes are determined by STR markers). Instead, they are determined by SNP's (single nucleotide polymorphisms) where a single base changes e.g. from A to G. These happen so rarely as to be considered unique.

However, there is a strong correlation between haplogroups and haplotypes so given any particular haplotype, it may be possible to correctly determine the haplogroup without any further tests (see Masterclass).

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heredity

 The transmission of characteristics (hair colour, facial features, genetic disorders etc.) from one generation to the next.

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heterogeneous

 Consisting of dissimilar or diverse ingredients or constituents.

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homogeneous

 Of uniform structure or composition throughout.

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junk DNA

 Most of the DNA in our bodies is termed ‘junk DNA’. It is non-coding (isn’t used for making proteins) and thus does not control medical function but is probably involved in genomic organization. Genetic genealogy only looks at the markers within junk DNA and thus the Y-DNA test cannot derive any medical information.

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locus (pl. loci)

 Latin for place. See marker.

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marker

 Also called a Locus (pl. loci). A gene of a known location on a chromosome. See STR marker. The DNA Heritage Y-DNA test uses 21 STR markers.

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microsatellite

 See STR marker

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mitochondrial DNA

 mtDNA - The circular DNA contained inside the mitochondria. The mitochondria are small organelles residing in animal cells which provide the power to the cell. They occupy about one-fifth of each cell. The mtDNA is passed from mother to her offspring (both sons and daughters), but only the daughter will pass it on.

The DNA sequence can be read and compared against a standard sequence (the Cambridge Reference Sequence) and deep (i.e. several thousands of years), but very broad genealogies can be deduced. A mtDNA haplogroup can usually be assigned for any given sequence.

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MRCA

 The Most Common Recent Ancestor between two people. For example, for two 1st cousins, their shared grandparent is the MRCA. If the cousins were both boys, they would share their grandfather’s Y-chromosome.

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mtDNA

 See Mitochondrial DNA.

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multiplex reaction

 Used in the PCR method, it utilises a ‘cocktail’ of chemicals so that many different markers (or loci) may be copied and tagged at the same time.

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mutation

 Any inheritable change in DNA sequence. Mutations usually occur as a result of miscopying by cell enzymes. Because the Y-chromosome has relatively few regions that control genetic function and is mostly ‘junk-DNA’, mutations in this 'junk DNA' cause no adverse effects and can therefore occur quite frequently.

A mutation at an STR marker may cause a particular allele to change from 11 repeats to 12 repeats – the son will therefore carry the 12 allele.

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mutation rate

 The estimated rate of mutational change is estimated to be approximately one mutation per 500 transmission events (0.2%) for any given STR marker. Using 21 different markers, it is reasonable to expect one mutation every 24 transmission events. However, these changes are random and thus can take place at any time.

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nucleic acid

 DNA and RNA are both nucleic acids. They are long polymer structures made up of nucleotides.

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nucleotide

 A single unit of nucleic acid. In DNA they are composed of phosphate, deoxyribose (a sugar), and either a purine (for adenine and guanine) or pyrimidine (for cytosine and thymine) base.

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nucleus

 The central structure of a cell that contains the genetic material.

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PCR

 Polymerase chain reaction - A process carried out in a test tube that produces millions of copies of small sections of DNA. Using a heat resistant enzyme (DNA polymerase) and a mixture of other chemicals, cycles of hot and cold temperatures essentially photocopy a particular marker (or locus) of the DNA many times.

Fluorescent tags are added to each copy so that they may be detected using laser analysers. A technique called multiplexing enhances the process.

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pharmacogenomics

 Pharmacogenomics is the testing of individuals to predict their genetic pre-disposition to drug response. The field of study looks at how genetic variations among the population affect drug response. It involves the analysis of genomic data to develop a screening process for more efficient clinical trials and molecular diagnostic tests used to determine individualized drug responses. It also looks at how a new targeted drug therapy could be developed using genomic data and analysis.

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polarized

 To break up into opposing factions or groupings. Used herein to refer to uneven BioGeographical Ancestry admixture results such as 95% East Asian/5% Native American as opposed to a relatively even mix such as 50%/50%.

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polymorphism

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

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population

 A group of individuals residing in a given area at a given time.

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restriction enzyme

 A protein that recognizes specific, short nucleotide sequences and cuts DNA at those sites. Bacteria contain over 400 such enzymes that recognize and cut over 100 DNA sequences. Snake venoms are sometimes also used.

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sequencing

 Determination of the order of nucleotides (base sequence) in a DNA or RNA molecule or the order of amino acids in a protein.

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sex chromosomes

 X and Y-chromosomes - Chromosomes involved in sex determination. Females have two X chromosomes, males have one X and one Y-chromosome. The Y-chromosome is thus only found in males.

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Single Nucleotide Polymorphism (SNP; pronounced snip)

 A precise base pair position where different people are found to vary in sequence. Generally two alternate alleles are found at a particular SNP. At least 2,000,000 SNPs are now known and there may be over 30,000,000 in the human genome.

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STR marker

 Short Tandem Repeats marker - A stretch of DNA where a small base sequence (usu. 2-6 base-pairs) repeats itself several times, giving a particular allele. For example, at the STR marker DYS391, the base sequence may read TCTA TCTA TCTA TCTA TCTA TCTA TCTA TCTA where TCTA is repeated eight times.

Choosing markers that have been proven to have high variation between and within populations is desirable.

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thymine

 Designated by the letter T, it is a pyrimidine base. One of the four base molecules present in DNA.

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transmission event

 The birth of a baby boy i.e. the effective passing on of the Y-chromosome.

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Y-chromosome

 The sex chromosome that instructs a foetus to grow into a baby boy. It is passed down from generation to generation only through the male line i.e. from father to son, father to son, etc. It is approx. 60 million base-pairs long.

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