Paternity testing (Forensic Science)
During the 1920’s, paternity testing was done using the ABO blood group types. This test could exclude a man as the father of another person, but it could not prove that a man was the father. The ABO blood group types are caused by the particular modification of a specific red blood cell surface protein called H antigen. The A and B genes code for enzymes that put specific sugars on the H antigen, and the O gene does not modify the H antigen. The human blood types are A, B, AB, and O; A and B are codominant, and O is recessive. A person has two ABO blood group genes, one from each parent. Based on the father’s and mother’s blood types, the blood type of the offspring can be determined. If a man has AB blood, he cannot have children with blood type O; a man with blood type AB thus would be excluded as the father of a blood type O child. By the 1930’s, paternity testing also began to take into account other red blood cell surface proteins, such as Rh, Kell, and Duffy blood groups.
During the 1970’s, human leukocyte antigens (HLAs) were used for paternity testing as well as for typing for organ transplants. HLAs are abundant in white blood cells, are in all cells of the body except red blood cells, and are used by the immune system to detect foreign cells. Each person has a unique set of HLA proteins inherited from parents. The usefulness of HLA type to determine paternity depends on how unusual (rare) a man’s HLA type is in the...
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DNA Tests for Paternity (Forensic Science)
During the 1980’s, DNA (deoxyribonucleic acid) profiling was developed. DNA analysis can be used to determine paternity conclusively, but this procedure requires large amounts of intact DNA. English geneticist Alec Jeffreys and his colleagues studied minisatellites made of a DNA sequence that is tandemly (end-to-end) repeated hundreds of times. These are called restriction fragment length polymorphisms (RFLPs) or variable number of tandem repeats (VNTRs). Individuals vary in the numbers of tandem repeats of the DNA sequence in their genomes. To detect these RFLPs, analysts isolate DNA and add a restriction enzyme (which makes sequence-specific cuts in DNA) to make cuts outside the repeating sequence. Gel electrophoresis is used to separate the DNA based on size. The DNA fragments are transferred from the gel to a membrane called a Southern blot, and a single-stranded, labeled DNA probe that is complementary to the repeating sequence is hybridized with the DNA on the membrane. This labeled probe allows the VNTR regions to be detected among all the DNA in the genome. The size of the fragment detected varies depending on the number of tandem repeats the individual has. This is length polymorphism—length variation from individual to individual.
During the 1990’s, polymerase chain reaction (PCR) became available to analyze DNA. Using sequence-specific primers, specific segments of DNA are amplified. Small quantities...
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Further Reading (Forensic Science)
Brinkmann, B. “Is the Amelogenin Sex Test Valid?” International Journal of Legal Medicine 116, no. 2 (2001): 63. Brief article addresses the use of the amelogenin gene for sex determination.
Cho, Mildred K., and Pamela Sankar. “Forensic Genetics and Ethical, Legal, and Social Implications Beyond the Clinic.” Nature Genetics 36 (2004): S8-S12. Discusses the ethical considerations related to DNA and genetic analysis.
Dawid, A. Philip, Julia Mortera, and Vincenzo L. Pascali. “Non-fatherhood or Mutation? A Probabilistic Approach to Parental Exclusion in Paternity Testing.” Forensic Science International 124, no. 1 (2001): 55-61. Addresses the effects of mutations on paternity tests.
Fisher, Barry A. J. Techniques of Crime Scene Investigation. 7th ed. Boca Raton, Fla.: CRC Press, 2004. Provides a broad overview of many areas of forensics, including DNA and RFLP typing.
Kobilinsky, Lawrence F., Thomas F. Liotti, and Jamel Oeser-Sweat. DNA: forensic and Legal Applications. Hoboken, N.J.: Wiley-Interscience, 2005. Presents a general overview of the uses of DNA analysis.
Petkovski, Elizabet, Christine Keyser-Tracqui, Rémi Hienne, and Bertrand Ludes. “SNPs and MALDI-TOF MS: Tools for DNA Typing in Forensic Paternity Testing and Anthropology.” Journal of Forensic Sciences 50, no. 3 (2005): 535-541. Provides details regarding single...
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