Exam_2_Review_butler_ch_15_team_1 - -Dye blobs are...

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Butler Chapter 15 – STR Genotyping Issues -Multiplex STR kits typically use various dye colors to resolve different peaks on electropherograms. -DNA fragments on electropherograms can be sized by using an internal size standard, usually labeled with a different color dye. -Off-ladder alleles or microvariants are alleles that are not complete repeat sequences. -For example, a TH01 allele three base pairs larger than allele 8 is designated 8.3. -Off-ladder alleles can be detected by re-injecting, re-amplifying or amplifying the sample with single-locus primers. -Stutter products are additional peaks present on electropherograms that may be mistaken for actual alleles. -Laboratory validation studies should be conducted to define maximum percent stutter for each locus. -Incomplete nucleotide addition can be cause by too much DNA template. -A longer final extension of PCR can remedy this problem by allowing Taq polymerase to add the additional nucleotide to the end of PCR products.
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Unformatted text preview: -Dye blobs are artifacts that result from the fluorescent dyes coming off of their respective primers and floating through the capillary by itself.-Dye artifacts can be filtered out after PCR by using filtration columns.-Air bubbles, urea crystals and voltage spikes can also result in false peaks.-These peaks are usually not reproducible, so re-injection of the sample should solve the problem.-When interpreting the results to determine genotypes, the analyst should rely on validation studies, his/her own experience and literature results to understand anomalies on electropherograms.-When comparing two or more samples, three possibilities exist: a match, exclusion or inconclusive.-For matches, three other possibilities exist: the suspect deposited the sample, the suspect did not deposit the sample (population genetics) and the suspect did not deposit the sample but laboratory error resulted in a false positive (lab mistakes)....
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This note was uploaded on 09/08/2010 for the course JS 113 at San Jose State University .

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