Assessment of STR profiles - An Introduction to Forensic Genetics - page 89

PCR product reduces with increased size

100 bp 160 bp 300 bp

Figure 7.11 TheprofilewasgeneratedusingtheAmpF STR Profiler Plus kit from Applied
Biosystems. The DNA was extracted from a bone recovered from a Scottish loch after approximately
30 years. The profile is typical of a degraded profile with a gradual reduction in the amount of
product as the amplicons increase in size

D3S1358

vWA

FGA allelic range

Figure 7.12 TheprofilewasgeneratedusingtheAmpF l STR Blue kit from Applied Biosystems.
The DNA was extracted from muscle tissue recovered from a plane crash. The muscle had been
subjected to high temperatures and the DNA was highly degraded; no amplification products were
detected from the FGA locus. The size standard is also shown as the red peaks

larger loci are barely detectable [29]; the decrease in amplification is gradual as the
length of the alleles increases.
In the second example an example of locus drop out can be seen, the first two
blue loci, D3S1358 and vWA have amplified successfully but there is no FGA allele.
This profile is from human muscle tissue that had been exposed to high temperatures
and has degraded to the extent that there is very little or no DNA that is 200 bp or
longer [30].
The interpretation of degraded profiles can be difficult and particular attention has
to be taken when homozygous loci are detected - are they really homozygous and
not heterozygous with one of the alleles having dropped out? When the levels are