9,422
edits
No edit summary |
No edit summary |
||
Line 1: | Line 1: | ||
In humans, there are different types of DNA: Autosomal DNA, X-DNA, Y-DNA, and Mitochondrial-DNA. Autosomal DNA is the most commonly used type of DNA used for research, but the other's have value as well. | |||
== Autosomal DNA == | == Autosomal DNA == | ||
Line 30: | Line 13: | ||
[https://isogg.org/wiki/Y_chromosome_DNA_tests Sex Chromosomes]: There are 22 pairs of autosomal DNA. The 23rd and final pair are the sex chromosomes which come in two variants, X, and Y. Females have two X chromosomes, and males have an X and a Y. The X chromosome is about as big as chromosome 7 and the Y is about as big as chromosome 21. In other words, the X chromosome is about 3 times bigger than the Y chromosome. Because they are so different in size, during recombination in males, the two try to line up at but can only perform recombination at the tip (in females the two X chromosomes recombine without any problems). The father gives the child all of his X or all of his Y. If he gives X, the child becomes a biological female if he gives Y the child becomes a biological male. Because of this rule, both have unique inheritance patterns. | [https://isogg.org/wiki/Y_chromosome_DNA_tests Sex Chromosomes]: There are 22 pairs of autosomal DNA. The 23rd and final pair are the sex chromosomes which come in two variants, X, and Y. Females have two X chromosomes, and males have an X and a Y. The X chromosome is about as big as chromosome 7 and the Y is about as big as chromosome 21. In other words, the X chromosome is about 3 times bigger than the Y chromosome. Because they are so different in size, during recombination in males, the two try to line up at but can only perform recombination at the tip (in females the two X chromosomes recombine without any problems). The father gives the child all of his X or all of his Y. If he gives X, the child becomes a biological female if he gives Y the child becomes a biological male. Because of this rule, both have unique inheritance patterns. | ||
'''X-DNA:''' X DNA is similar to autosomal DNA except that a man never inherits it from his father. This allows some lines to be eliminated based on the presence of matching X DNA. For example, if a man shares X DNA with another person, that person must be related on the man's mother's side. A female inherits X DNA from her father, but all of that DNA comes from her father's mother (her paternal grandmother). A female will never inherit any X DNA from her paternal grandfather. | '''X-DNA:''' X DNA is similar to autosomal DNA except that a man never inherits it from his father. This allows some lines to be eliminated based on the presence of matching X DNA. For example, if a man shares X DNA with another person, that person must be related on the man's mother's side. A female inherits X DNA from her father, but all of that DNA comes from her father's mother (her paternal grandmother). A female will never inherit any X DNA from her paternal grandfather. All of the major DNA companies test the X chromosome as part of their package, but only 23andme reports matches on the X chromosome. | ||
'''Y-DNA:''' The Y chromosome is only passed down father to son and only males have a Y chromosome. The Y chromosome does not go through the recombination process so the only way it can change is through spontaneous mutations. These mutations are usually harmless and the only way you can know if you have one is by taking a Y-DNA test. | '''Y-DNA:''' The Y chromosome is only passed down father to son and only males have a Y chromosome. The Y chromosome does not go through the recombination process so the only way it can change is through spontaneous mutations. These mutations are usually harmless and the only way you can know if you have one is by taking a Y-DNA test. [[Ancestry DNA in Genealogy Research|Ancestry]], [[23andme in Genealogy Research|23andme]], [[MyHeritage DNA in Genealogy Research|MyHeritage]], and [[Living DNA in Genealogy Research|Living DNA]] all test the Y-chromosome as part of their autosomal package and 23andme even predicts your haplogroup, but only [[FamilyTreeDNA in Genealogy Research|FamilyTreeDNA]] sells specialized tests that generate lists of genetic relatives using the Y chromosome. | ||
Y-DNA has several advantages for genetic genealogists. It mutates at a faster rate than mtDNA and at a rate that is more useful for genealogists. By comparing the Y-DNA of two individuals it is possible to determine how closely the two are related on the direct male line. Anyone who matches your Y-DNA test is related on both your and their direct paternal line. The common ancestor will always be a man who had at least two sons, one of which you descend from and the other that the match descends from. Because Y-DNA can only change through mutations, it can be used to find relatives on the direct male line up to 25 generations back whereas autosomal DNA is usually only helpful up to about 5 generations back. Because Y-DNA and surnames are usually both passed down father to son, Y-DNA surname projects exist that try discover how everyone with the same surname is related | Y-DNA testing has several advantages for genetic genealogists. It mutates at a faster rate than mtDNA and at a rate that is more useful for genealogists. By comparing the Y-DNA of two individuals it is possible to determine how closely the two are related on the direct male line. Anyone who matches your Y-DNA test is related on both your and their direct paternal line. The common ancestor will always be a man who had at least two sons, one of which you descend from and the other that the match descends from. Because Y-DNA can only change through mutations, it can be used to find relatives on the direct male line up to 25 generations back whereas autosomal DNA is usually only helpful up to about 5 generations back. Because Y-DNA and surnames are usually both passed down father to son, Y-DNA surname projects exist that try discover how everyone with the same surname is related. | ||
The biggest disadvantage to Y-DNA research is far less people have taken Y-DNA tests than they have autosomal DNA tests. The only way to overcome this obstacle is for more people to test. The other disadvantage is that Y-DNA can only reveal information about your direct male line. If you wanted to use Y-DNA to research your mother's father's surname, for example, your Y-DNA would not work. You would need to test your maternal grandfather or another close relative related on the direct male line. | The biggest disadvantage to Y-DNA research is far less people have taken Y-DNA tests than they have autosomal DNA tests. The only way to overcome this obstacle is for more people to test. The other disadvantage is that Y-DNA can only reveal information about your direct male line. If you wanted to use Y-DNA to research your mother's father's surname, for example, your Y-DNA would not work. You would need to test your maternal grandfather or another close relative related on the direct male line. | ||
Line 45: | Line 28: | ||
One major disadvantage to mtDNA is that it mutates at a slow rate. A person whose mtDNA perfectly matches yours could be related through a common ancestor that lived anytime within the past 500 years. Also the direct maternal line usually has a different surname at every generation so surname projects are useless. | One major disadvantage to mtDNA is that it mutates at a slow rate. A person whose mtDNA perfectly matches yours could be related through a common ancestor that lived anytime within the past 500 years. Also the direct maternal line usually has a different surname at every generation so surname projects are useless. | ||
edits