9,422
edits
no edit summary
No edit summary |
|||
| Line 12: | Line 12: | ||
== Single-nucleotide polymorphisms (SNPs) == | == Single-nucleotide polymorphisms (SNPs) == | ||
All human beings are 99.9% identical in their genetic makeup meaning that at out of the 3 billion genes we all have 99.9% are the same in all humans. The places where it is possible for a variance to occur are called, SNP's which stands for Single-nucleotide polymorphisms. SNP's are the main force behind DNA and what gives it it's genealogical value. When two individuals have enough matching SNP's in a row, this becomes a matching segment. The more matching SNP's there are, the bigger the segment is. If a segment is big enough (bigger than 15cm's), | All human beings are 99.9% identical in their genetic makeup meaning that at out of the 3 billion genes we all have 99.9% are the same in all humans. The places where it is possible for a variance to occur are called, SNP's which stands for Single-nucleotide polymorphisms. SNP's are the main force behind DNA and what gives it it's genealogical value. When two individuals have enough matching SNP's in a row, this becomes a matching segment. The more matching SNP's there are, the bigger the segment is. If a segment is big enough (bigger than 15cm's), then the segment must be identical by descend (IBD) which means the two individuals share that segment because they both descend from a common ancestor who passed on that segment of DNA to both of them. The more matching segments there and the bigger they are, the closer two test takers are probably related. By testing a sample of a person's SNP's and then comparing them to everyone else in the database, it is possible to identify a person's genetic relatives. Most major companies will test 500-600k SNP's. | ||
In theory each SNP can be one of the four nitrogenous bases (A, C, G, or T), but in practice only two are ever found at each specific spot the vast majority of the time. There is usually a major alle that is present in about 95% of test takers and a minor alle that is present in about 5% of test takers. Each person will have two nitrogenous bases at each spot, one inherited from their mother and one inherited from their father. This means that at each SNP tested a person can have one of three combinations: two copies of the major alle (called a homozygous SNP), one copy of the major alle and one copy of the minor alle (called a heterozygous SNP), and two copies of the minor alle (called a homozygous SNP). | |||
== Autosomal DNA == | == Autosomal DNA == | ||