DNA fingerprinting
DNA fingerprinting is a set of methods that can be used to determine the identity of people from a biological sample based on sequence polymorphisms of selected sections of DNA. Today, this method of individual identification is widely used both in criminal cases (forensic genetics) and in civil disputes, especially in connection with determining parentage (paternity disputes). In both cases, the results of DNA fingerprinting often serve as the main evidence.
Polymorphisms that DNA fingerprinting uses
- RFLP (restriction fragment length polymorphism)
It allows the distinction of two individuals according to two alleles. Allele 1 carries a restriction endonuclease recognition site, allele 2 does not. So if the suspect's genotype is 1/1 and, for example, the biological traces found at the crime scene are of the genotype 1/2 or 2/2. A suspect may be excluded. However, since there can only be 3 different genotypes for a simple two-allelic polymorphism, the discriminatory power of a single polymorphism of this type is very small. Therefore, it is necessary to use more variable polymorphisms and combine the results of the examination of several loci. This fact and the need for a relatively large amount of high-quality DNA, together with the time requirement, mean that the RFLP method is not commonly used.
- VNTR (variable number of tandem repeats)
The method, also called multilocus fingerprinting, is based on the detection of alleles from many different VNTRs from different chromosomes. After using the probe, we get a series of stripes of different intensity and different distances. Except for identical twins, the distribution of stripes is not the same in any two individuals. When determining paternity, it is examined whether the multilocus fingerprinting contains the same bands as the father's fingerprinting. If so, the child is indeed his offspring. However, even this method is hindered by the need for a large amount of high-quality DNA to use the Southern method.
- STR (short tandem repeats)
The principle of the method using short tandem repeats is the same as for VNTR. However, STR markers are used most often, mainly due to their greater sensitivity and less time-consuming nature.
Laboratory procedure
- DNA collection
- PCR (Polymerase Chain Reaction)
- Electrophoresis
- Presentation of results
Links
- Briefly about fingerprinting (English)
Reference
GOETZ, Petr, et al. Vybrané kapitoly z lékařské biologie, díl 2. 1. vydání. Praha : Karolinum, 2002. 139 s. ISBN 80-246-0320-9.
