ATA stutter product formation

CTAT CTAT

CTAT CTAT

CTAT CTAT

5000

4000

2000

s 10

s 10

TH01 1

TPOX |

CSF1PO |

D7S820

III1

1 i *

, I

1 h

-r 1

ra c 10

D5S818

VWA j fr

"FttH"

D3S1358 T

D8S1179

D13S317

Alleles jÖ

I 10

Alleles

FGA || D16S539 | | D18

S51

D21S11 I

Ll

f

, ll

1 1 Ll'lt

Ll

1

_

Ölt TL.

Jll

irr

Alleles

Figure 6.3

Stutter percentages for 13 CODIS STR loci (data adapted from AmpFlSTR manuals). Alleles for each STR locus are shown from smallest to largest. Each locus has a different average stutter percentage but all loci show the trend of increasing stutter with larger alleles (longer number of repeats).

Because stutter products are the same size as actual allele PCR products, it can be challenging to determine whether a small peak is a real allele from a minor contributor or a stutter product of an adjacent allele.

Mixture interpretation requires a good understanding of the behavior of stutter products in single source samples. Often a laboratory will quantify the percentage of stutter product peak heights compared to their corresponding allele peak heights. The percentage of stutter product formation for an allele is determined simply by dividing the stutter peak height by the corresponding allele peak height.

A plot of the alleles from each of the 13 standard STR loci reveals variation in the percentage of stutter for each locus as well as alleles from the same locus (Figure 6.3). Such a plot illustrates several important principles. First, each locus has a different amount of stutter product formation. Second, longer alleles for a STR locus exhibit a greater degree of stutter than smaller alleles for the same locus. Third, stutter percentage with the standard tetranucleotide repeats is generally less than 15% for all 13 CODIS core STR loci under standard amplification conditions.

Was this article helpful?

0 0
Stammering Its Cause and Its Cure

Stammering Its Cause and Its Cure

This book discusses the futility of curing stammering by common means. It traces various attempts at curing stammering in the past and how wasteful these attempt were, until he discovered a simple program to cure it. The book presents the life of Benjamin Nathaniel Bogue and his struggles with the handicap. Bogue devotes a great deal of text to explain the handicap of stammering, its effects on the body and psychology of the sufferer, and its cure.

Get My Free Ebook


Post a comment