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DNA Basics: Difference between revisions
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[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. | ||
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. | '''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. | ||
'''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 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. Such projects can be less effective with common names like Smith, but can be extremely effective with unique surnames like Tolman. | 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. Such projects can be less effective with common names like Smith, but can be extremely effective with unique surnames like Tolman. | ||
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May disclose information you weren’t expecting such as: | May disclose information you weren’t expecting such as: | ||
*Adoptions | *Adoptions: You may learn you were adopted. | ||
*Illegitimacies | *Illegitimacies | ||
*Non-paternal events (NPEs; where parentage may be unexpected) | *Non-paternal events (NPEs; where parentage may be unexpected): You may learn, for example that the main who raised you, is not your biological father or that your siblings are really your half-siblings. | ||
*Name changes | *Name changes | ||