Biology Reference
In-Depth Information
Table 13.2
The Y chromosome STR loci that are commonly used in forensic analysis
Minimal haplotype
PowerPlex
Y pF
STR
Yfiler
Extended haplotype
DYS19
DYS19
DYS19
DYS19
DYS385 a/b
DYS385 a/b
DYS385 a/b
DYS385 a/b
DYS389 I
DYS389 I
DYS389 I
DYS389 I
DYS389 II
DYS389 II
DYS389 II
DYS389 II
DYS390
DYS390
DYS390
DYS390
DYS391
DYS391
DYS391
DYS391
DYS392
DYS392
DYS392
DYS392
DYS393
DYS393
DYS393
DYS393
DYS438
DYS437
DYS437
DYS439
DYS438
DYS438
DYS439
DYS439
DYS448
DYS456
DYS458
DYS635
GATA H4
The Y chromosome is effectively digitized, and based on the example in
Figure 13.4 can be represented as a series of 17 numbers, making comparisons and
database searching relatively simple. The result of a search of the yhrd is shown in
Figure 13.5.
Forensic applications of Y chromosome polymorphisms
That the Y chromosome is only found in males makes it a valuable tool, in par-
ticular for the analysis of male and female mixtures after sexual assaults when
differential DNA extraction is not possible; Y STR analysis has been successful
with female - male ratios of up to 2000:1 [65]. The presence of male DNA has also
been detected when vaginal swabs were analysed, even when no spermatozoa have
been detected - either through the assailant being azoospermic (1 - 2% of rape cases)
or through the deterioration of the spermatozoa [62, 66]. The Y STRs can also be
used to detect the presence of two male profiles; the interpretation of the mixtures
depends on the presence of major and minor contributors [65].
Y chromosome profiling has also been used for paternity testing and is particularly
valuable in deficient cases, where the alleged father is not available for testing. In
these cases, any male relative who is paternally related to the alleged father can be
used as a reference. An extreme example of where this has been used is the paternity
analysis that linked the third US president, Thomas Jefferson, to the child of one
of his slaves, Sally Hemings [67, 68]. Cases involving human identification have
also used the Y chromosome as a tool to link remains to paternal family members,
and as with deficient paternity cases the use of the Y chromosome is particularly
advantageous when there are no parents or children to use as reference material; it
also simplifies the sorting of the material following mass disasters [69].
