Allelic ladders

This SRM contains human cells from two cell culture lines from which DNA can be extracted, genomic DNA from those two cell lines plus eight individuals, PCR-amplified DNA from the two cell lines plus four of the eight individuals, a D1S80 allelic ladder for characterization of amplified DNA, and a DNA size marker to assure proper electrophoretic separations. 

FIGURE 1.5 Dye-labeled DNA fragments are produced by PCR with dye-labeled primers (a). The size of two different alleles (b) with 7 or 5 repeats (4 bp) differs from that of 8 bp. By coseparation of a size standard (c, black Unes) and an allelic ladder (c, gray Unes), the size can be determined and the alleles determined correctly. 

FIGURE 1.11 Comparison of data from Genotyper analysis. Comparing PCR products with fragments of allelic ladders, intra- and interlaboratory data exchange is possible. Upper panel allelic ladder of markers D3S1358, THOl, andD18S51 used for human identification shown at the lower panel DNA profiles from four different DNA samples. 

FIGURE 25.2 AmpF/STRTMIdentifiler kit allelic ladder. A separation of the most common aUeles for each STR loci. The SIR analysis software utilizes this ladder as an external standard to assign the correct alleles to evidence samples such as is illustrated in Figure 25.1. Notice the presence of two base variant alleles (from the normal four base STR repeat) at the D21, D18, D19, and FGA lod. There is also a one base variant allele located in the THOl locus. (Courtesy of Ada Nunez, Florida International University.)... 

FIGURE 37.5 Electropherograms of (a) Promega PowerPlex 16 allelic ladder and (b) Applied Biosystems AmpFlSTR Profiler Plus allelic ladder obtained on the p.CAE microdevice shown in Figure 37.4. (Reproduced from Yeung. S. H. et al., J Forensic Sci 2006, 51, 740-747. Copyright 2006. With permission from Blackwell Publishing, Inc.)... 

Butler, J.M., li, J., Shaler, T.A., Monforte, J.A., and Becker, C.H. (1999) Reliable genotyping of short tandem repeat lod without an allelic ladder using time-of-flight mass spectrometry. Int. J. Legal Med., 112 (1), 45-49. 

The major difference in the typing of the STR loci is the ability to include an internal size standard if the detection device used has multicolor capability. Under the TWG-DAM Guidelines forensic samples are to be placed adjacent to an allele ladder, as seen in Fig. 7 (PCR-STR). Since the Beckman Genomyx SC only has two filters (fluorescein and TMR) an internal ladder could not be used, so the adjacent ladder format is used. In this situation there is no special preparation for detection. When the four-color Hitachi FMBIO II Fluorescent Scanner, ABI Prism 377 or 310 is used, an internal standard is used to size the DNA fragements. As part of the electrophoresis setup a ROX ladder is added to PE Biosystems amplified products while a CRX ladder is added to Promega kits. (See Figure 8 for example.) Amplified products including the... 

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