Intro to forensic profiling

• DNA

  • Deoxyribonucleic acid
  • double helix molecules <— 4 nucleotides base pairs: A,T,G,C
  • sugar phosphate sides and backbones
  • order of nuclotides determines genetic code
• DNA 


  is molecule of life and genetic blueprint
• DNA is found

  • WBC
  • Hair
  • bone
  • teeth
  • tissue
  • saliva
  • semen
  • urine
• types of DNA

  1. nDNA: nunclear DNA: genes and chromo: 46 chromo: 22 auto and 1 sex
  2. mtDNA: maternal inheritance “circular”
• allele drop in 


  alleles that are not derived from known donor of the profile and maybe from contamination
• allele drop out


  occurs when a sample is typed and 1+ alleles are not present, usually due to low quality DNA
• how long can DNA survive

  • DNA degrades with exposure to environment ie. temp, UV and humidity
  • fragile skin cells are not persistent
• Locard principle 


  2 bodies of objects come into contact with one another, they transfers their material to each other
• can DNA solve crime


  No, its used as a tool to assist police
• list places DNA is the gold standard

  • target police invest
  • exonerate innocent
  • increase likelihood of confession
  • strengthens breif of evidence
  • pre-trail
  • crime prevention
• steps of DNA typing

  1. sample prep/collection
  2. DNA extraction
  3. DNA purification
  4. DNA quantification
  5. PCR amplification
  6. analy sis
• 
  

  pp21 vs verifiler plus

  pp21: 20 auto and 1 sex chromo “amelogenin“

  VFP: 23 auto and 2 sex chromo ”amelogenin and y-indel” also control
• STR


  Short tandem repeats

  • short streches of DNA characterised by a unit
  • repeat present in number
  • used to disguise 1 person to another
• repeat regions vs flanking region

  repeat: variable between samples

  flanking: where PCR primers bind are constant
• homozygote vs heterozygous 


  homo: Both alleles are same length and number of repeats

  heto: alleles are different length and number of repeats
• nomenclature 


  D: DNA

  18: CHROMO 18

  S: SINGLE COPY

  51: 51ST LOCUS
• micro-variant 


  designated by the number of complete repeats and number of be of partial repeat serrated by bp

  • incomplete parts
• gene 


  unit of heredity and strech of DNA that codes for pro
• locus 


  septic location of the gene
• allele 


  variant of DNA seq or length at given locus