Forensic dna analysis
Download
1 / 11

Forensic DNA Analysis - PowerPoint PPT Presentation


  • 667 Views
  • Uploaded on

Forensic DNA Analysis Harris County Medical Examiner’s Office Joseph A. Jachimczyk Forensic Center Houston, TX *Presentation is automatic and will begin shortly. S hort T andem R epeat analysis, or STR analysis Uses nuclear DNA

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Forensic DNA Analysis' - liam


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Forensic dna analysis l.jpg

Forensic DNA Analysis

Harris County Medical Examiner’s Office

Joseph A. Jachimczyk Forensic Center

Houston, TX

*Presentation is automatic and will begin shortly.


Forensic dna technology used at the harris county medical examiner s dna laboratory l.jpg

Short Tandem Repeat analysis, or

STR analysis

Uses nuclear DNA

Forensic DNA technology used at the Harris County Medical Examiner’s DNA Laboratory


Slide3 l.jpg

Target Region for PCR

DNA in the Cell Nucleus

chromosome

cell nucleus

Double stranded DNA molecule

Individual nucleotides

Source: http://www.cstl.nist.gov/biotech/strbase/ppt/intro.ppt


Dna extraction l.jpg
DNA Extraction

  • DNA analysis begins with DNA extraction from biological evidence

  • DNA extraction is:

    • A chemical process by which DNA is released from cell(s)

    • Other cellular components are removed leaving a pure sample of DNA in an aqueous (liquid) solution


Slide5 l.jpg

Sources of Biological Evidence

Blood

Semen

Saliva

Urine

Hair

Teeth

Bone

Tissue

Perspiration

Vaginal secretions

Source: http://www.cstl.nist.gov/biotech/strbase/ppt/intro.ppt


Dna amplification l.jpg
DNA Amplification

  • After DNA extraction DNA is amplified using the Polymerase Chain Reaction (PCR)

  • PCR amplification makes many copies of the DNA to allow for detection (think photocopies)

PCR

DNA strand

Amplified DNA


Dna detection l.jpg
DNA Detection

  • Amplified DNA fragments are labeled with a fluorescent tag

  • DNA fragments are separated by electrophoresis (electric current)

  • The size of the fluorescent DNA fragment is determined by a machine which displays the information graphically.

  • Analysts read the graph to determine the DNA type


Dna analysis l.jpg
DNA Analysis

  • Short Tandem Repeats (STRs) are short stretches of DNA that are repeated several times at a particular location on a chromosome

  • The number of repeats and, therefore, the length of the Short Tandem Repeat DNA varies from person to person

  • Each individual has two different (or two equal) length repeats at the same location on a chromosome

  • STR DNA testing determines the length of the STR DNA at 13 different chromosomal locations

  • STR DNA testing analysis is the most commonly used forensic DNA analysis method


Slide9 l.jpg

13 CODIS Core STR Loci with Chromosomal Positions

A listing of all lengths at each location (loci) is called a DNA profile

TPOX

D3S1358

TH01

D8S1179

D5S818

VWA

FGA

D7S820

CSF1PO

AMEL

D13S317

AMEL

D16S539

D18S51

D21S11

Source: http://www.cstl.nist.gov/biotech/strbase/ppt/intro.ppt


At a single str locus l.jpg

(4)

(5)

CAG CAG CAG CAG

CAG CAG CAG CAG CAG

(6)

(7)

CAG CAG CAG CAG CAG CAG CAG

CAG CAG CAG CAG CAG CAG

Father’s Type: 5, 6

Mother’s Type: 4, 7

(6)

CAG CAG CAG CAG CAG CAG

(4)

CAG CAG CAG CAG

Baby’s Type: 4, 6

At a single STR locus:

*(Other possibilities: 4, 5 or 5, 7 or 6, 7)


Statistics l.jpg
Statistics

  • The 13 STR DNA tests produce exceedingly rare DNA profiles

  • A STR DNA profile might be found in 1 person out of a quadrillion (that is, a billion million) people

  • A match between two DNA samples, say, a crime scene stain and the DNA of a suspect, can link a subject to a crime

  • A non-match may shift the focus away from a particular suspect