BASICS OF DNA FINGERPRINTING
![Picture](/uploads/1/0/6/5/10651471/1553872.jpg)
Most of our DNA is identical to each other, however, there are inherited regions of our DNA that can vary from person to person (such variations are termed as Polymorphisms). One such class of polymorphisms is known as tandem repeats, which vary within the individual of the species. This forms the basis of Genetic Fingerprinting.
Tandem repeats occur in DNA when a pattern of two or more nucleotides is repeated and the repetitions are directly adjacent to each other.
In a Eukaryotic genome, Tandem repeats are an array of consecutive repeats, known as Satellites. They are of three types based on migration when centrifuged in CsCl density gradient.
Satellite DNA consists of very large arrays of tandemly repeating, non-coding DNA. Satellite DNA is the main component of Functional Centromeres, and form the main structural constituent of the Heterochromatin.
The name "Satellite DNA" refers to how repetitions of a short DNA sequence tend to produce a different frequency of the nucleotides Adenine, Cytosine, Guanine and Thymine, and thus have a different density from bulk DNA - such that they form a second or 'satellite' band when genomic DNA is separated on a density gradient.The size of a satellite DNA ranges from 100 kb to over 1 Mb.This can be explained with the help of the graph below. [21],
Tandem repeats occur in DNA when a pattern of two or more nucleotides is repeated and the repetitions are directly adjacent to each other.
In a Eukaryotic genome, Tandem repeats are an array of consecutive repeats, known as Satellites. They are of three types based on migration when centrifuged in CsCl density gradient.
- Satellites.
- Minisatellites.
- Microsatellites.
Satellite DNA consists of very large arrays of tandemly repeating, non-coding DNA. Satellite DNA is the main component of Functional Centromeres, and form the main structural constituent of the Heterochromatin.
The name "Satellite DNA" refers to how repetitions of a short DNA sequence tend to produce a different frequency of the nucleotides Adenine, Cytosine, Guanine and Thymine, and thus have a different density from bulk DNA - such that they form a second or 'satellite' band when genomic DNA is separated on a density gradient.The size of a satellite DNA ranges from 100 kb to over 1 Mb.This can be explained with the help of the graph below. [21],
![Picture](/uploads/1/0/6/5/10651471/2944484.gif)
The size of a minisatellite ranges from 1 kb to 20 kb. One type of minisatellites is called variable number of tandem repeats (VNTR). Its repeat unit ranges from 9 bp - 80 bp. They are located in non-coding regions. The number of repeats for a given minisatellite differs between individuals. This feature is the basis of DNA fingerprinting. [6J]
![Picture](/uploads/1/0/6/5/10651471/5244797.jpg)
Microsatellites are also known as short tandem repeats (STR), because a repeat unit consists of only 1-6 bp and the whole repetitive region spans less than 150 bp. Similar to minisatellites, the number of repeats for a given microsatellite may differ between individuals. Therefore, microsatellites can be used for DNA fingerprinting.