Biology Reference
In-Depth Information
11
Kinship testing
The application of DNA profiling to kinship analysis is widespread and offers an easy
means of establishing biological relationships. Not surprisingly, paternity testing is
the most common form of kinship testing, with hundreds of thousands of tests being
performed worldwide each year [1]. Since the first DNA-based kinship test in 1985
[2], DNA analysis has been applied to larger numbers of kinship tests, to the testing
of more complex relationships and to the identification of highly compromised human
remains.
Parentage testing
PCR-based STR profiling has now become the standard tool and the PowerPlex
16
(Promega) and AmpF
STR
Identifiler
(Applied Biosystems) STR kits that can
analyse 15 loci simultaneously are routinely used (see Chapter 6). Laboratories that
undertake kinship testing often have over 20 genetic markers at their disposal, includ-
ing STR markers on the X and Y chromosomes [3, 4] that allow for the testing of
complex relationships [5]. SNPs have also been used for parentage testing [6, 7],
although this is still uncommon [8].
The sensitivity of STR analysis, although not essential for most forms of paternity
testing, allows samples to be routinely collected using buccal swabs [1] and has
expanded the possible scenarios where it can be used, for example the analysis of
low amounts of DNA recovered from fetal cells [9, 10] (Figure 11.1).
The methodology used to produce DNA profiles for paternity testing is identi-
cal to the analysis of material recovered from crime scenes (see Chapters 4 - 7).
However, the interpretation of results is more complex than when comparing pro-
files from crime scenes and suspects. If the tested child does not possess the alleles
that have been inherited from the biological father, we can conclude that he cannot
be the biological father. However, because mutations between the father and child
could lead to a false exclusion at any given loci [1, 11 - 14] it is standard prac-
tice that an exclusion at three or more loci is required before a test is declared
negative.
If we cannot exclude the tested man as being the biological father, then we have to
assign a value to indicate the significance of non-exclusion. Likelihood ratios (LRs)
