Paternity testing

Microsatellites-the repeated units are typically 2-4 bp, and the length of the entire repeat is generally less than 150 bp. This dass often referred to as STRs (simple tandem repeats) is most typically amplified by a PCR for paternity testing, forensic cases, or gene linkage analysis (see Section II, Chapter 4 Polymorphic Markers and Linkage Analysis). 

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. 

Paternity Testing Using PCR Amplification of Microsatellite Sequences... 

Paternity testing and the identification of genetic parents via DNA analysis has, within the last decade, become a highly reliable test upon which courts and medical staff increasingly rely. 

Figure 10.8. The RFLP for paternity testing. Step 1 (top) is the isolation and cleavage of native DNA into restriction fragments Step 2 (middle) is the agarose electrophoretic separation, which yields smears of indistinguishable bands and Step 3 (bottom) shows the pattern obtained after Southern blotting, hybridization with 32P labeled probes, and autoradiography.

Samples for identity testing can be any specimen that contains DNA. Samples obtained from an individual for paternity testing or as a reference sample to be compared with DNA prepared from evidence are usually peripheral blood or buccal mucosa. Samples useful for forensic testing, engraftment assays, and the identification of clinical samples may range from plucked hairs to bone marrow aspirates to paraffin embedded tissue. While subject to degradation over time in the presence of enzymes, acidic or basic conditions, or high temperature, DNA is a remarkably stable molecule that can be recovered and successfully analyzed from solutions, surfaces, and cells. 

Selection and validation of testing methods are key issues in paternity testing. Specific requirements for paternity testing may be mandated by local laws and agreements. Thus the choice of methods and genetic systems should be based on an agreement between the client(s) and the laboratory. 

Nonstandardized methods should not be used as the sole methods within a paternity testing laboratory. In addition, a nonstandard method should only be used if it can be documented that the method is used in at least one other laboratory, thus making it possible to obtain a second opinion based on repeated testing. 

In addition to the usual paternity test reports, laboratories are occasionally asked to provide interpretative reports when less than complete information is available. The usual report is discussed next and the interpretive reports are discussed afterwards. 

The alleles found at the analyzed loci may be entirely consistent with the accused man being the biological father of the child. In this case, the likelihood that he is truly the father rather than a random individual who is not excluded can be calculated. A number of assumptions underlie accurate calculations of the hkeliness of paternity. Tested individuals must be properly identified, testing must be accurate, and allele frequencies in relevant populations must be well characterized. 

The quality control and assurance measures for paternity testing are similar to those for other types of human identity testing. Positive identification of samples, prevention of DNA contamination, the use of control alleles of known size, and the validation of software employed for genetic analysis and calculation are among measures common to identity testing programs. Population distribution data for the systems used must be documented. In addition, mutation frequencies of the systems used must be dociunented and used appropriately. 

Elston RC. Probability and Paternity Testing. Am J Human Genetics 1986 39 112-22. 

AGTAGTAGTAGTAGT... ), etc. Due to polymerase slip (a.k.a. polymerase chatter), during DNA replication there is a slight chance these repeat sequences may become altered copies of the repeat unit can be created or removed. Consequently, the exact number of repeat units may differ between unrelated individuals. Considering all the known microsatellite markers, no two individuals are identical. This is the basis for forensic DNA identification and for testing of familial relationships (e.g., paternity testing). 

DNA fingerprinting is used for paternity testing and forensic identification of suspects. Which of the following is the most accurate description of DNA fingerprinting ... 

It should be noted that in performing family studies, it may, in some cases, be necessary to perform paternity testing in order to explain results which appear to be anomalous (Al, C22, M13). 

One extension of blotting techniques that is likely to be expanded considerably in the near future is DNA fingerprinting for forensic analysis, paternity testing, etc. Already, the dioxetane substrate for alkaline phosphatase has been shown to be a useful tool in this endeavor (G4). 

Paternity Test DNA fingerprint. This gel shows possible results of a DNA fingerprint from a paternity test. Lane 1 shows a DNA size ladder used as a control. Lane 2 is a DNA pattern from a mother. Lanes 3 and 4 are DNA patterns from possible fathers. Lane 5 is the DNA pattern from the child. Every band in the child s DNA must have a corresponding band in either the mother or the father s DNA Band A in the child s DNA matches a band in the mother s DNA and in the prospective father s DNA in lane 4. However, band B in the child s DNA is not seen in the mother s DNA, nor is it seen in either of the prospective fathers DNA. This excludes both possible fathers from being the father of the child. 

How can differences in DNA from individuals be seen The ability to analyze DNA fragments is important for basic research and for forensic science. DNA fingerprinting allows for the identification of individuals from their DNA samples. DNA is digested with restriction enzymes, and a banding pattern is seen upon electrophoresis of the digest. No two individuals have the same pattern, just as no two people have the same fingerprints. This technique is often used for paternity tests and for identification of criminals. 

Short DNA repeats often appear as multiple copies in higher genomes, positioned in a head-to-tail orientation, and are known as tandem repeats. The number of copies of these repeats varies between individuals and between chromosomes within an individual s genome. This hypervariability, known as polymorphism, can be exploited in paternity testing and forensics. 

Tits 33.15 Paternity testing GuUberg, Tegelstrom Gelter (1992)... 

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