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Emma Chowdhury

EBSCOhost: FORENSIC TRICHOLOGY AND ITS IMPORTANCE IN CRIME CASES. - 0 views

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Emma Forensic DNA Scientific Article

shared by Emma Chowdhury on 11 Feb 13 - No Cached
  • Emma Chowdhury on 11 Feb 13
     
    Trichology is the scientific study of hair. To use trichology successfully to solve crimes, there has to be a piece of skin or blood attached to the hair. 
Kareena M

EBSCOhost: FORENSIC TRICHOLOGY AND ITS IMPORTANCE IN CRIME CASES. - 1 views

web.ebscohost.com/...pdfviewer

Kareena Forensic DNA article

shared by Kareena M on 11 Feb 13 - No Cached
  • Kareena M on 11 Feb 13
     
    Finding DNA in hair samples
Abraham H

Forensic Techniques [Media 4] - 0 views

www.ornl.gov/...forensics.shtml

abraham hew Forensic DNA media 4

shared by Abraham H on 01 Mar 13 - Cached
  • RFLP is a technique for analyzing the variable lengths of DNA fragments that result from digesting a DNA sample with a special kind of enzyme. This enzyme, a restriction endonuclease, cuts DNA at a specific sequence pattern know as a restriction endonuclease recognition site. The presence or absence of certain recognition sites in a DNA sample generates variable lengths of DNA fragments, which are separated using gel electrophoresis. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample. RFLP was one of the first applications of DNA analysis to forensic investigation. With the development of newer, more efficient DNA-analysis techniques, RFLP is not used as much as it once was because it requires relatively large amounts of DNA. In addition, samples degraded by environmental factors, such as dirt or mold, do not work well with RFLP.
  • PCR Analysis Polymerase chain reaction (PCR) is used to make millions of exact copies of DNA from a biological sample. DNA amplification with PCR allows DNA analysis on biological samples as small as a few skin cells. With RFLP, DNA samples would have to be about the size of a quarter. The ability of PCR to amplify such tiny quantities of DNA enables even highly degraded samples to be analyzed. Great care, however, must be taken to prevent contamination with other biological materials during the identifying, collecting, and preserving of a sample.
  • Short tandem repeat (STR) technology is used to evaluate specific regions (loci) within nuclear DNA. Variability in STR regions can be used to distinguish one DNA profile from another. The Federal Bureau of Investigation (FBI) uses a standard set of 13 specific STR regions for CODIS. CODIS is a software program that operates local, state, and national databases of DNA profiles from convicted offenders, unsolved crime scene evidence, and missing persons. The odds that two individuals will have the same 13-loci DNA profile is about one in a billion.
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  • Mitochondrial DNA analysis (mtDNA) can be used to examine the DNA from samples that cannot be analyzed by RFLP or STR. Nuclear DNA must be extracted from samples for use in RFLP, PCR, and STR; however, mtDNA analysis uses DNA extracted from another cellular organelle called a mitochondrion. While older biological samples that lack nucleated cellular material, such as hair, bones, and teeth, cannot be analyzed with STR and RFLP, they can be analyzed with mtDNA. In the investigation of cases that have gone unsolved for many years, mtDNA is extremely valuable. All mothers have the same mitochondrial DNA as their offspring. This is because the mitochondria of each new embryo comes from the mother's egg cell. The father's sperm contributes only nuclear DNA. Comparing the mtDNA profile of unidentified remains with the profile of a potential maternal relative can be an important technique in missing-person investigations.
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