Autosomal STR

• do identical twins have the same dna

  yes, they do due to coming from the same egg and sperm and thus the same origin
• how can you tell the differences between indentical twins

  1. fingerprints
  2. whole genome sequence
• what do inhibitor affect

  • they affect larger fragments more than smaller fragments = drop out
• explain what allele frequencies indicate

  the prevalence of specific allele in a pop
• define partial dna profile

  20 STR, 12 allele matches
• define random match prob


  LR x genotype freq from data base
• VFP


  25 overall, 23 autosomal , 2 sex chromo and 1 internal control
• list things you can see with VFP

  • internal quality control: only shows S and L allele in blue channel
  • this is quality assurance for any inhibitors (IQCS AND IQCL)
• what does it mean if there is a Y but no Y indel

  could be due to contamination and degradation and that alleles are shared in common
• lineage marker 


  passed down from 1 gen without changing expect for mutation
• autosomal markers 


  STR loci and shullfed with each gen, half from mom and half from dad
• haplotype 


  linage marker
• paternal vs maternal 


  pat: y chromo

  mat: x chromo and mtDNA
• counting method

  • used for lineage markers
  • depends on pop suspect belongs to and database pop
  • larger size of database = more accurate LR
• y chromo DNA markers

  1. ministatillites
  2. STR
  3. bi-allelic markers (SNP)
• y-str


  sensivity <100pg male DNA with 28 cycle PCR
• why Y chromosomes

  1. applications
  2. advanatges for paternal lineage and mutli people
  3. needs
• list the forensic value of Y-str

  1. deling with vasectomised males
  2. high levels of female dna ie. sexual assaults
• x chromo makers

  1. SNP: single nucleotide polymorphism
  2. SSR: simple seq repeats
  3. mini VNTRS
  4. microstats
  5. insert and delettions
• mini-STR

  • primers are closer to STR repeat region
  • reduces size of STR applicants
  • allows degraded DNA and low levels of DNA, to increase success of profiling
• disadvantages of mini-STR

  1. multiples are diffcult due to size of amp product is so close
  2. caution surrounding binding site mutation