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Polymorphisms can be used to illuminate fundamental biological patterns and processes. By studying polymorphisms in a group of wild animals, the familial relationships (brother, sister, mother, father, etc.) between them can be determined. Also, the amount of interbreeding between different groups of the same species (gene flow) can be estimated by studying the polymorphisms they contain. This information can be used to identify unique populations that may be important for survival of the species. Sometimes it is not immediately obvious if two different groups of organisms should be classified as different species. Comparing the genetic polymorphisms in the two groups aids in making a judgment as to whether they warrant classification as different species.

If enough polymorphisms are analyzed, it is possible to distinguish between individual humans with a high degree of confidence. This method is known as DNA profiling (or DNA fingerprinting) and provides an important tool in law enforcement. A person's genotype, or DNA profile, can be determined from very small samples, such as those that may be left at a crime scene (hair, blood, skin cells, etc.). The genotype of samples found at the crime scene can then be compared to a suspect's genotype. If they match, it is very likely that the suspect was present at the crime scene. Currently, the FBI uses thirteen different polymorphic loci for DNA fingerprinting. In a similar manner, analysis of polymorphisms can help prove or disprove fatherhood (paternity) in cases where responsibility for a child is disputed. see also Gel Electrophoresis; Linkage and Recombination; Mapping; Mutation; Repetitive DNA Elements.

R. John Nelson

Bibliography

Avise, John C. Molecular Markers, Natural History and Evolution. New York: Chapman & Hall, 1994.

Weaver, Robert F., and Philip W. Hedrick. Genetics, 2nd ed. Dubuque, IA: William C. Brown, 1992.

Internet Resource

SNPs: Variations on a Theme. National Center for Biotechnology Information. <http:// www.ncbi.nlm.nih.gov/About/primer/snps.html>.

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