Keywords (Extracted from title, table of contents and
abstract of thesis)
Sexual, Frequencies, Specimens, Testimony, Spermatozoa, Potential,
Allele, Haplotypes, Assault, Victims, Characterisation |
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Abstract
Sexual assault is a
violent crime and a significant problem faced by any developing
society. Identification of spermatozoa is the biological evidence
most often sought in specimens from sexual assault victims. Absence
of spermatozoa usually terminates biological investigations, and the
victim’s testimony is contested. DNA with high discrimination
potential and sensitivity obtained in an unbiased manner would be
highly advantageous in sexual assault cases with negative results.
Cervico-vaginal, oral and anal swabs were collected from 930 sexual
assault cases, within a period from July 2006 to December 2007. In a
total of 930 cases, 300 cases (32.25%) were found cytologically
negative. Y-Chromosomes were detected in 108/300 (36%) cases, a
fairly high percentage indeed for victims whose testimony would have
been contested otherwise. Y-chromosome was also evidenced in the
population of victims examined after 72 hours of sexual assault.
Spermatozoa are rarely detected at such intervals, so medical men
are reluctant to take samples, but our studies show that swabs ought
to be taken from victims for Y-Chromosome DNA typing even after long
lapses of time between sexual assaults and medical examination. Y-
STRs are also very useful in detecting the male DNA fraction in
male/ female DNA mixture where amount of female DNA is present in a
far excess amount. It can also provide evidence in old and
wasted samples.
Eleven Y-STR(short tandem repeats), namely DYS 19, DYS385 a,b,
DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS438, DYS439,
residing on the Ychromosome and amelogenin recognized by an
international body “The Scientific Working Group on DNA Analysis
Methods” (SWGDAM) were chosen and amplified simultaneously using
polymerase chain reaction (PCR) by the Y-PLEXTM 12 system,
asensitive, valid, reliable, and robust multiplex system. Amelogenin
provided results for gender identification and served as internal
control for PCR. It did not adversely affect the amplification of Y-STRs
in mixture samples containing male and female DNA.
amplification of Y-STRs in mixture samples containing male and
female DNA. After assurance of quality standards in accordance with
the instructions laid down by DNA advisory Board (DAB), population
data from Punjab was collected and comparison made with studies from
other global population groups in addition to 12 ethnic groups from
Pakistan. It showed greater genetic similarity with Africa, West
Asia, and Europe but not with China & Japan. Arlequin version 3.0, a
standard software for haplotyping analysis was used, the value of
haplotype diversity is 0.9766 +/- 0.0074, gene diversity 0.67619
with standard deviation 0.10293. The value of average diversity over
loci is 0.672759 +/- .354019. The mean number of pair wise
differences are 6.727587 +/- 3.196717.
Therefore, after adopting a proper strategy of designing and
optimising multiplex system for Y-STRs, we can successfully resolve
the matters of individual identification,determination of
perpetrators of violent sexual crime, of unestablished paternity and
paternal lineage.
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