Biology Reference
In-Depth Information
(a) (b)
Figure 6.7 During electrophoresis the computer software records the fluorescence levels at regular
time points and these are recorded as data points. The DNA fragments that make up the internal-
lane size standards are plotted against the data points. An example of the sizing curves that are
produced from (a) the GeneScan -500 standard (Applied Biosystems) and (b) the ILS600 (Promega
Corporation) are shown using the local Southern method to generate the size calling curve
Amelogenin
D8S1179
D21S11
D18S51
} amelogenin
} D8S1179
} D21S11
} D18S51
Figure 6.8 The green loci from a profile produced using the AmpF STR SGM Plus kit. The size
of each peak has been calculated along with the peak heights and areas. The first amelogenin peak
was detected after 13.13 minutes (which is when data point 3579 was taken) and is estimated to
be 103.33 bp long, the peak area is 20 712 rfu and the peak height 4058 rfu
differ by only 1 bp, the use of allelic ladders that contain all the common alleles
(Figure 6.9) at each locus has been adopted by the forensic community to ensure
accurate profiling [16, 43]. Unlike the internal-lane size standards the allelic ladders
cannot be analysed in the same injection as the samples, but are run periodically
during the analysis of a batch of samples.
When assigning the alleles, the unknown peaks are compared with the allelic ladder
and should fall within a 1-bp window, that is
0.5 bp of the allelic ladder size; if the
unknown alleles differ by more than this then they are classified as off-ladder (OL)
±
Search WWH ::




Custom Search