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Autosomal DNA (atDNA): This makes up about 95% of human DNA. It consists of 22 pairs of chromosomes and in each pair, one is from mom and one is from dad. The pairs of chromosomes are simply names 1, 2, 3, etc... 21, 22. They are mostly named by their size with chromosome 1 being the largest, chromosome 2 being the second largest etc. They are not perfectly named by their size, for example chromosome 22 is actually bigger than chromosome 21, chromosome 20 is slightly bigger than chromosome 19 etc. This is because as our understanding of DNA grows and improves, some chromosomes turned out to be a little bigger or smaller than we initially thought. | Autosomal DNA (atDNA): This makes up about 95% of human DNA. It consists of 22 pairs of chromosomes and in each pair, one is from mom and one is from dad. The pairs of chromosomes are simply names 1, 2, 3, etc... 21, 22. They are mostly named by their size with chromosome 1 being the largest, chromosome 2 being the second largest etc. They are not perfectly named by their size, for example chromosome 22 is actually bigger than chromosome 21, chromosome 20 is slightly bigger than chromosome 19 etc. This is because as our understanding of DNA grows and improves, some chromosomes turned out to be a little bigger or smaller than we initially thought. | ||
Autosomal DNA is the most important and most commonly tested type of DNA. A child will have exactly half of their autosomal DNA from each parent. However, a child will usually not have exactly 25% from each grandparent. A child could have 20% from one grandparent and 30% from another grandparent for example. This is because each child is randomly given half of their parent's DNA. When a new sperm or egg is formed, the pairs chromosomes in the parent line and exchange information, meaning segments are randomly cut out and switch places with each other to form new chromosomes that are a mixture of the previous ones. The child is then given one chromosome from each pair and the other is discarded. | Autosomal DNA is the most important and most commonly tested type of DNA. A child will have exactly half of their autosomal DNA from each parent. However, a child will usually not have exactly 25% from each grandparent. A child could have 20% from one grandparent and 30% from another grandparent for example. This is because each child is randomly given half of their parent's DNA. When a new sperm or egg is formed, the pairs chromosomes in the parent line and exchange information, meaning segments are randomly cut out and switch places with each other to form new chromosomes that are a mixture of the previous ones. The child is then given one chromosome from each pair and the other is discarded. This happens in both parents so that the child receives one full set of chromosomes from each parent. | ||
== Y-DNA == | == Y-DNA == | ||
[https://isogg.org/wiki/Y_chromosome_DNA_tests Y-DNA]: The term Y-DNA refers to the Y-Chromosome. 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. This is the second most valuable type of DNA. Although females do not have Y-DNA, they can get the same information by testing a close male relative such as a father or brother. | [https://isogg.org/wiki/Y_chromosome_DNA_tests Y-DNA]: The term Y-DNA refers to the Y-Chromosome. 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. This is the second most valuable type of DNA. Although females do not have Y-DNA, they can get the same information by testing a close male relative such as a father or brother. | ||
== Mitochondrial DNA == | |||
*Mitochondrial DNA (mtDNA): Mitochondrial DNA is unique. The rest of human DNA is located in the nucleus of the cell and is divided into chromosomes. Mitochondrial DNA on the other hand resides in the cell's mitochondria (the part that provides most of the cell's energy) and it is connected in a circle just like bacterial DNA. It is also the smallest portion of human DNA being about only 16,000 base pairs long. In other words, it is about one third the size of the smallest chromosome. These unique properties cause mitochondrial DNA to be have a special place among genetic genealogists. One advantage of mtDNA are that because it resides outside the nucleus, it can only be inherited from the mother. Sperm only contains a cell's nucleus and anything outside of that only comes from the mother's egg. This means that it does not go through recombination and testing your mtDNA can reveal information about your ancestor's on your direct maternal line. The other major advantage to mtDNA is that it decomposes slower than the rest of your DNA so it is more likely to be used for solving cold cases when the person of interest is no longer alive to test. It was by using mtDNA that the remains of Richard III were conclusively identified, for example. | |||
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. | |||
== Why use it in family history research? == | == Why use it in family history research? == | ||