Forensic medicine polymorphisms

DNA sequences as short as 50-100 bp and as long as 10 kb can be amplified. Twenty cycles provide an amplification of 10 and 30 cycles of 10. The PCR allows the DNA in a single cell, hair follicle, or spermatozoon to be amplified and analyzed. Thus, the applications of PCR to forensic medicine are obvious. The PCR is also used (1) to detect Infectious agents, especially latent viruses (2) to make prenatal genetic diagnoses (3) to detect allelic polymorphisms (4) to establish precise tissue types for transplants and (5) to study... 

There is a normal variation of DNA sequence just as is true of more obvious aspects of human structute. Variations of DNA sequence, polymorphisms, occur approximately once in evety 500 nucleotides, or about 10 times per genome. There are without doubt deletions and insertions of DNA as well as single-base substitutions. In healthy people, these alterations obviously occur in noncoding regions of DNA or at sites that cause no change in function of the encoded protein. This heritable polymorphism of DNA structure can be associated with certain diseases within a large kindred and can be used to search for the specific gene involved, as is illustrated below. It can also be used in a variety of applications in forensic medicine. 

Most repetitive sequences are not in coding regions. Because expansion of these sequences in spacer DMA rarely affects any function, they become highly polymorphic in the population and can be used to develop a genetic fir erprint. Such fingerprints are important in paternity testing and forensic medicine. Very small samples containing dried tissue can be analyzed by this technique. 

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