DNA Short Tandem Repeats Organism DNA Short Tandem Repeats Organ - PowerPoint PPT Presentation

Stochastic variation Examples so far assume allele calls are certain, but low template samples cause new problems because of stochastic variation. • Stochastic variation is random variation • Failure to reproduce results • Leads to uncertainty

The crimestain

Standard technique Enough sample so that no dropout is expected and peak height represents amount of DNA present (i.e. not variable)

Low Template Sample • Stochastic variation is random variation • Failure to reproduce results • Leads to uncertainty

A B C D E F H G I

B A D C F E

Dropout or dropin? D8 D21 D7 CSF D3 THO1 D13 D16 D2 D19 vWA TPOX D18 D5 FGA 11 21 8 10 16 6 12 17 14 8 14 22 10 11 17 9 11 13 19 13 15 11 15 12 24 13 31.2 11 12 18 9.3 12 14 25 14 16 12 16 13 25 8 6 9 29 10 7 11 12 14 20 31.2 11 11 16 8 12 13 17 13 16 8 14 12 21 13 32.2 12 12 18 9.3 13 14 25 14 18 11 16 13 24

Probability of dropout and dropin p(D) Is the probability that an allele is really there but you have not detected it. p(C) Is the probability that an allele you have detected is not from the crimestain – it is contamination