Y-STR POLYMORPHISMS IN

FORENSIC CASEWORK

Mgr. Jana Odlerová

Institute of Forensic Science Slovak Police Corps

Y Chromosome

-small ~60 Mb total DNA sequence

(only chromosome 22 is smaller)

- acrocentric

- linear DNA

- haploid

- uniparental lineages

- male-specific

- genetic variation at multiple points

along the Y chromosome is combined

to form a Y haplotype for a sample

Y ch

Ľudský X a Y chromozóm

Human X a Y Chromosome

~ 2.5 Mb on tips recombine with X (pseudoautosomal regions)

~ homologous regions on human X and Y chromosome except pseudoautosomal regions

Why the Y Chromosome?

• Applications- forensic investigations (98% of violent crime by men)

- genealogical purposes - evolutionary studies

• Advantages to Human Identity Testing - male component isolated without differential extraction - paternal lineages

• Needs - population studies to evaluate diversity of haplotypes - robust assay for accurate characterization of Y markers

Y Chromosome DNA Markers

• STRs (microsatellites) - DYS19, DYS385, etc. - mostly tetranucleotide repeats

• Bi-allelic markers (unique event polymorphisms--UEP)

- SNPs (single nucleotide polymorphisms) - Y Alu polymorphism (YAP) or other insertions/deletions (“indels“)

• Minisatellites - MSY1 (DYF155S1) composed of 48-114 copies of a 25 bp repeat unit

with 5 sequence variant repeat types - typed by MVR-PCR (minisatellite variant repeat)

Map of Y Chromosome STR Markers

Y-Plex™6 - include 6 Y-STRs (Reliagene Technologies, Inc.)

Y-Plex™5 - include 5 Y-STRs (Reliagene Technologies, Inc.)

PowerPlex™Y System - include 11 Y-STRs (Promega)

Y-Plex™12 - include 11 Y-STRs + amelogenin (Reliagene Technologies, Inc.)

AmpFLSTR Yfiler™ PCR Amplification Kit - 17 Y-STRs (Applied Biosystems)

Current Forensic Y STR Multiplexes

Advantages of Using Y Chromosome in Forensic Casework

- limited amount of biological material (optimal is 0,3 ng DNA)

- partially degraded DNA

- absence of consanguineous biological relatives – parents, children

- mixtures of DNA in rape cases (15 pg male DNA:150 ng female DNA)

- mixtures of DNA from three or more individuals (at least one man)

- male DNA present at trace levels

Disadvantage – individual identification

THANK YOU FOR ATTENTION