Title

Novel Y-STR typing strategies reveal the genetic profile of the semen donor in extended interval post-coital cervicovaginal samples

Authors

Authors

A. Hall;J. Ballantyne

Abbreviated Journal Title

Forensic Sci.Int.

Keywords

multiplex Y-STR analysis; post-coital cervicovaginal samples; rape; evidence; DYS19; DYS385; DYS388; DYS389; DYS390; DYS391; DYS392; DYS393; DYS425; DYS434; DYS437; DYS438; DYS439; Y-GATA-C4; Y-GATA-A7.1 (DYS460); Y-GATA-A7.2 (DYS461); Y-GATA-H4; SPERMATOZOA; DNA; PERSISTENCE; CHROMOSOME; VAGINA; POLYMORPHISMS; CERVIX; Medicine, Legal

Abstract

For a variety of reasons, some victims of sexual assault provide vaginal samples more than 24-36 h after the incident. In these cases, the ability to obtain an autosomal STR profile of the semen donor from the living victim diminishes rapidly as the postcoital interval is extended. We have used a number of carefully selected Y-STR loci in a variety of multiplex or monoplex. formats to extend the post-coital interval from which a genetic profile of the semen donor can be obtained. The proposed Y-STR typing strategies enable the routine detection of the male donor Y-STR haplotype in cervicovaginal samples recovered up to 4 days post-coitus. We attribute our success to a number of factors that significantly improve the sensitivity and specificity of the analysis. Firstly, we utilize a subset of Y-STR loci that have been carefully selected for their superior performance under stressed conditions in both multiplex and monoplex formats. Specifically these loci function with low copy number templates in the presence of a vast excess of potentially confounding female DNA. Secondly, sperm and non-sperm DNA is co-extracted without a differential extraction process to prevent the unnecessary loss of the small number of structurally fragile sperm remaining in the cervicovaginal tract several days after intercourse. Thirdly, low copy number detection is facilitated by increasing the cycle number to 34-35 cycles and by the ability to input up to 450 ng of co-extracted sperm/non-sperm DNA into the PCR reaction without the appearance of confounding female artifacts. Lastly, the proper collection of post-coital cervicovaginal samples, instead of the lower or mid-vaginal tract samples often taken, is required for optimal recovery of sperm for analysis. In this report we demonstrate that our previously described 19 Y-STR loci systems (MPI and MPII) permit a reliable high resolution haplotype determination of the semen donor in cervicovaginal samples taken up to 48 h after intercourse. However, as the post-coital interval is extended further, dramatic loss of signal is observed and haplotype determination of the male donor is no longer possible with MPI and MPH. Nonetheless, subsets of these 19 loci (MPA and MPB) have been developed specifically to detect the male haplotype in samples recovered 4 days after intercourse. Thus, it is possible to derive an 11-19 locus Y-STR profile of the semen donor in cervicovaginal samples recovered 2-4 days after intercourse. (C) 2003 Elsevier Ireland Ltd. All rights reserved.

Journal Title

Forensic Science International

Volume

136

Issue/Number

1-3

Publication Date

1-1-2003

Document Type

Article

Language

English

First Page

58

Last Page

72

WOS Identifier

WOS:000185496600008

ISSN

0379-0738

Share

COinS