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Genetics
- Ad-mixture (aka Ethnicity Mix)
- Allosomes (Sex chromosomes X & Y)
- Autosomes (Chromosomes 1-22)
- Base Pair
- CE Testing (1st Wave)
- centiMorgan (cM)
- Chromosomes
- Clade
- Cladogram
- dbSNP, rsID, NIH, etc
- Deoxyribonucleic Acid (DNA)
- Derived & Ancestral
- Endogamy or Pedigree Collapse
- epigenetics
- Gene
- Genetic Marker
- Genome Build (aka Reference Model)
- Genotyping
- Haplogroup
- Haploid & Diploid
- Haplotype
- Imputation
- Low Coverage Sequencing
- Meiosis & Mitosis
- Microarray Testing (2nd Wave)
- Microarray File Formats (aka RAW)
- Mito Build (rCRS, Yoruba, RSRS)
- Mitochondria
- Modal
- Null Allele
- Pangenome
- Phylogenetic Tree
- Probes, Primers, Adaptors and Tags
- Recombination (aka Cross-Overs)
- Sampling Techniques
- Sequencing (3rd Wave)
- Sequencing File Formats
- Single Nucleotide Polymorphism (SNP)
- Short Tandem Repeat (STR)
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Genealogy
- Ahnentafel number
- Ancestor and Descendant
- Birth, Marriage and Death (BMD)
- Branches
- Consanguinity
- Cousins
- Deep Ancestry
- Earliest Known Ancestor (EKA)
- Family (Nuclear, and Household)
- Genealogical Exchange Database (GEDCom)
- Genealogical Proof Standard (GPS)
- Genealogical Records
- Genealogical Time Frame (aka last 500 years)
- Genealogical Tool
- Genealogical Trees
- Generation Difference (GD)
- Individuals
- Most Recent Common Ancestor (MRCA)
- Née
- Not Parent Expected (NPE)
- One-Tree (aka World Tree)
- Patriline & Matriline
- Places
- Repositories
- Siblings
- Sources
- Surname, One-Name and Family Branch Studies
- Years Before Present (ybp)
- (Genetic Genealogy) Terms
- Genetics Industry
- (Genetic Genealogy and Ancient DNA) Industry
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- Allosomes (Sex chromosomes X & Y)
The Allosomes (or Sex chromosomes) are the 23rd pair of nuclear DNA that exist in cells. This as compared to the autosomes, that are known as chromosomes 1 to 22. Or the mitochondria which is the only DNA that exists outside the nucleus in the general cell body. Allosomes are unique for a number of reasons. In the human genome, the allosomes are the X and Y chromosomes.
First, as is now well known, the X and Y chromosomes determine the biological sex of the person. Biological females have two X chromosomes while biological males have an X and a Y. There are some anomalies that exist in nature but this characterizes most in the human species.
Second, for the most part, the Y chromosome does not recombine with any other chromosome. As a result, it is very stable for many generations. And hence the usefulness in a surname study to tag the Patriline family branch back for hundreds of years.
Thirdly, a father does not pass down his X chromosome to his son, Only either the fathers' X or Y chromosome will exist in the sperm that fertilizes an egg and thus determine the sex of the resultant embryo. A father always passes his Y to a son.
Fourthly, the X chromosome, in the male or father, does not recombine when passed down to a daughter (for the most part). Note that a daughter will always get this "mostly intact" X chromosome from their father. Whether it can be recreated in test results (by phasing) is another issue. But this leads to unique characteristics of the X. Segments will survive longer down alternating male-female ancestral lines. Statistically twice as long in such instances as recombination with the other X will only happen every other generation. Long X matching segments, when autosomal matching segments are short, may indicate an MRCA along a mostly alternating male-female lineage.
Finally, the two X chromosomes in females behave like the autosomes. So in a Matriline, the X chromosome and autosomes equally share in recombination each generation. A Matriline loses the longer matching segments on the X chromosome the quickest and in-step (statistically) with the autosomes. (But the mtDNA helps make up for that down these lines as it does not recombine being an isolated DNA strand.)
When returning autosomal test results in a RAW Data File (that typically include the xDNA also), the female testers result will include values coming from both of their X chromosomes; just as it does for the autosomes. The male testers result will either simply replicate the single X value in the tuple returned for each SNP or may include the values of the recombining tips (aka ((Pseudo-Autosomal Regions|PAR), PARs) of the Y chromosome in the corresponding X chromosome result. The non-recombining part of the Y chromosome is always reported separately and often as a 24th chromosome if not marked directly as the Y value.
In the text, when you see xDNA, we mean the X chromosome and X testing. Similarly, for yDNA we mean the Y.
Early on within the site, we mistakenly adopted a term "somal" to mean the allosomes. In reality, it is just the autosomes and allosomes That has been corrected where found.
First, as is now well known, the X and Y chromosomes determine the biological sex of the person. Biological females have two X chromosomes while biological males have an X and a Y. There are some anomalies that exist in nature but this characterizes most in the human species.
Second, for the most part, the Y chromosome does not recombine with any other chromosome. As a result, it is very stable for many generations. And hence the usefulness in a surname study to tag the Patriline family branch back for hundreds of years.
Thirdly, a father does not pass down his X chromosome to his son, Only either the fathers' X or Y chromosome will exist in the sperm that fertilizes an egg and thus determine the sex of the resultant embryo. A father always passes his Y to a son.
Fourthly, the X chromosome, in the male or father, does not recombine when passed down to a daughter (for the most part). Note that a daughter will always get this "mostly intact" X chromosome from their father. Whether it can be recreated in test results (by phasing) is another issue. But this leads to unique characteristics of the X. Segments will survive longer down alternating male-female ancestral lines. Statistically twice as long in such instances as recombination with the other X will only happen every other generation. Long X matching segments, when autosomal matching segments are short, may indicate an MRCA along a mostly alternating male-female lineage.
Finally, the two X chromosomes in females behave like the autosomes. So in a Matriline, the X chromosome and autosomes equally share in recombination each generation. A Matriline loses the longer matching segments on the X chromosome the quickest and in-step (statistically) with the autosomes. (But the mtDNA helps make up for that down these lines as it does not recombine being an isolated DNA strand.)
When returning autosomal test results in a RAW Data File (that typically include the xDNA also), the female testers result will include values coming from both of their X chromosomes; just as it does for the autosomes. The male testers result will either simply replicate the single X value in the tuple returned for each SNP or may include the values of the recombining tips (aka ((Pseudo-Autosomal Regions|PAR), PARs) of the Y chromosome in the corresponding X chromosome result. The non-recombining part of the Y chromosome is always reported separately and often as a 24th chromosome if not marked directly as the Y value.
In the text, when you see xDNA, we mean the X chromosome and X testing. Similarly, for yDNA we mean the Y.
Early on within the site, we mistakenly adopted a term "somal" to mean the allosomes. In reality, it is just the autosomes and allosomes That has been corrected where found.