Beckman Coulter CEQ 8000, Руководство пользователя

Страница: 264 / 382

Fragment Analysis Procedures
250 CEQ™ 8000 Genetic Analysis System
5. Selecting this check box enables the system to
detect stutters longer than
(occurring after) the allele
.
Spurious Peak Detection
Spurious peaks are generally small trace artifacts that are detected as a result of sample
contaminants. These peaks tend to have a different shape than fragment peaks but
often fall within the size range of a locus tag and are detected. However, they generally
do not meet the criteria to be identified as known alleles and are therefore labeled as
“spurious” peaks.
The
Spurious Peak Detection
area allows you to direct the system to look for
spurious peaks in your analysis. You can specify a height threshold under which the
system will identify a peak as contaminant and not include it in your allele list.
1. Select the
Detect spurious peaks
check box if you want the system to remove
any peaks which are below the maximum height threshold for spurious peaks.
2. Specify the
maximum height percent of the spurious peak
relative to the
true allele below which detected peaks are considered spurious peaks.
+A Detection
+A Detection is an allele calling criteria which is used to compensate for a common
DNA polymerase phenomenon of adding a “non-templated” Adenine to the ends of
PCR products. What results is a mixture of PCR products of different lengths from a
single allele. Some of these products are templated “true length” (called “-A”
products) while others are one nucleotide longer (called “+A” products).
The ratio of these two types of products can vary greatly between different reactions
and primers. The result of having different fragment sizes from a single allele
complicates the interpretation of fragment analysis data. Instead of one peak for one
allele, there are often two that represent the same allele spaced one nucleotide apart.
The
+A Detection
area of the window allows you to specify how the system will
differentiate between the true allele and the +A allele artifact.
More than one of these check boxes can be selected at a time. Read
through the following descriptions or refer to the tables below to see
how these selections will A Detection.
Apparent size inA
Selecting this check box indicates to the system that the sizes entered into the
Apparent Size column of the allele list were for the +A fragments. The parameter
affects where the software looks for peaks when identifying alleles.
/- A
If the
/- A
box is checked , the software will identify in the fragment list
either the +A or -A peaks. The software will then identify one of them as the true allele
based upon your selection in the
Use +A peak to call allele
check box. The other
peak will then be designated as A or -A accordingly.