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DNA Analysis

Human body contains 60 trillion cells
1. Each cell has a Nucleus except red blood cells
  1. Each nucleus contains genetic material such as Chromosomes, genes and DNA. It weights 7 picograms 7 x 10^-12 g
    1. DNA
      1. Cannot be found directly at crime scene however biological materials containing DNA can be found
        Blood, semen, saliva, skin cells, hair and body parts contain DNA
      2. Packaged as 23 pairs of chromosomes
        22 pairs containing genetic information
        1 pair of sex determining chromosomes XY- Male , XX - Female
        No. of genes in the genome varies from species to species. Complex organisms have more genes. Humans: 30,000 Bacteria: 100- 1000
        Chromosomes contain genes.Different chromosomes contain different genes
        However ,each pair of chromosomes are Homologus
        Same size, contain same genetic structure. One from mother; one from father
        Made up of coding regions - Genes and non-coding regions ( 90- 95% of DNA AKA Junk DNA)
        Genes are made up of base pairs. A single gene contains 1000 - 10 000 base pairs
      3. DNA composition
        2-Deoxyribose
        Phosphate
        Bases
        Adenine
        Guanine
        Cytosine
        Thymine
        Combination of these 2-Deoxyribose, Phospate and Bases is also known as Nucleotide
        DNA is basically 4 Nucleotides joining together. Phospate joins together with the sugar
        DNA structure
        Double helix shape bonded together by bases through hydrogen bond
        Complementary base-pairing A&T, C&G
      4. Genetic Code
        Proline = CCT
        Glutamate = GAG
        CCT GAG GAG = Hemoglobin
        Wrong coding would give rise to diseases
      5. Mitochondrial DNA (mtDNA)
        More robust than nuclear DNA More resistant to sample degradation
        However, inherited strictly from mother. This means that it is not unique to individual
        The Romanovs, Russia's imperial family was executed during the Russian Revolution in 1918
        Remains burned and buried. MTdna extracted
        Prince Philip, Duke of Edinburgh shared same maternal line as Tsarina Alexandra
        Bones found matched Prince Philip's mtDNA. Remains were that of Romanov's family
        Berlin, 1920s. Woman claimed to be Grand Duchess Anastasia. DNA from a tissue surgical sample was extracted. Matched to a person name Franziska Schanzkwoska
Discovered by Sir Alec Jeffreys
Uses Non-coding region (Junk DNA) as there is high variability from person to person
Techniques used
1. Gel electrphoresis Similar to TLC
2. Capillary Gel electrophoresis Similar to GC
Polymerase Chain Reaction (PCR)
1. Method of multiplying DNA through a Thermal Cycler
  1. Each cycle takes 5 minutes. Typically run 25 -35 times. It will multiply by 1 milllion times
    1. This means that, very small amounts can be analyzed
Fragment of interests in DNA are called Short Tandem Repeats (STR)
1. STRs consist of sequence of 3 - 7 base pairs that are repeated
  1. What differentiate individuals are the number of times that STRs are repeated
2. Multiplexing: Technique used to analyze multiple STRs simultaneously
  1. The higher the number of STR used, the better the probability of identifying an individual
3. One from father, One from mother
4. However, this technique cannot be directly applied to siblings
  1. Except for Identical Twins as they have identical DNA that cannot be differentiated by Forensic Scientist
    1. Malaysia 2009,. One guy arrested for drugs possession . Has an identical twin and police unsure which twin was guilty. -->Presumption of innocence
      1. Identical twins do not have 100% identical DNA however more Advanced techniques are required to test and they are more expensive
        Marseilles, France. Series of rape cases and DNA extracted matches identical twins. In order to differentiate the two twins by DNA analysis, it would cost 30 milion euros
Cases
1. 1st Case DNA profiling was used: Colin Pitchfork
  1. Narborough, England, 1983. Lynda Mann, raped and murdered
    1. 1986, Dawn Ashworth raped and murdered in the same manner
      1. Richard Buckland confessed to murder of Dawn Ashworth but not Lynda Mann
        Samples were taken from both crime scene and Richard's DNA did not match the samples. He was innocent
        1987, DNA screening of local men blood type A. There was no match
        A lady overheard Ian Kelly taking the DNA test under the name of Colin Pitchfork
        Colin Pitchfork was arrested and his DNA matched the DNA from crime scenes. Confessed to both murders and was sentenced to life in prison
2. Lesley Molseed, 1975. Sexually assaulted and stabbed to death
  1. Stefan Kiszko wrongfully imprisoned for 16 years
    1. In 2006, case was reopened. DNA extracted matched Ronald Castree
      1. Ronald Castree convicted and sentenced
3. 1975, Yorkshire Ripper. Murdered prostitutes and women
  1. 1978, Several letters sent to police. Cassette tape with Ripper's voice. Believed to be Genuine
    1. Sent police in the wrong direction
      1. 1981, Yorkshire Ripper , Peter Sutcliffe was caught after 7 attacks and 3 murders
        2005. Case reoopened. DNA extract from glue of envelope led to John Humble. Sentenced for preventing the course of justice
4. First used in UK.. 1985, Kirk Bloodsworth convicted of rape-murder of Dawn Hamilton
  1. Insisted on innocence. In 1993 DNA test of semen did not match Kirk Bloodsworth. Released from Prison
    1. 2003. DNA matched Kimberly Shay Ruffner
5. James Bain guilty of rape in 1974 based on eye witness testimony. 2009, DNA proved innocence. Compensated US 1.75M
6. 1988, Lynette White stabbed to death. Three men convicted but conviction was quashed later on
  1. Reinvestigation of Crime Scene
    1. Bloodstains preserved under paint. DNA extracted but there was no match
      1. However, theres unusua feature in DNA causing 1 person to stand out
        Teenager with motoring offence. Cannot be him because he was not born yet. It was then traced to his Uncle, Jeffrey Gafoor. Convicted of Murder eventually
7. Maricop, Arizona 1992. Woman murdered. Body dumped at an abandoned factory.
  1. Suspect apprehended but denied having been at murder site. Seed pods were found on back of his truck. They matched the DNA of Palo verde tree at the crime scene
8. Australia 2001, Peter Falconio & Joanne Lees driving in northern territory
  1. Stopped by driver, shot and was killed
    1. Joanne Lees captured but escaped. Peter Falconio never found. Found bloodstain on the floor.
      1. Suspected Bradley Murdoch.
        Blood on Joanne Lees shirt Bradley Murdoch. DNA on gear stick of campervan matched Bradley Murdoch. DNA on strap used to tie Joanne Lees hand matched Joanne Lees Dr Peter (forensic scientist) and Bradley Murdoch
        Without DNA, can only detect blood type on shirt, which gives a 30:1 possibility of individualizing. Other evidences would be useless
        Bradley Murdoch was convicted. If not for DNA, there would be no case

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	Created by iamkomj over 11 years ago