Relationship testing

• relationships testing “kinship”


  comparing DNA profiles to determine relationships b/w 2 indivs
• paternity testing 


  connecting father to child
• reverse paternity 


  connecting child from father
• maternity 


  mother —> child
• reverse maternity 


  child from mother
• compare 3 different relationship analysis

  1. family relationships: adoptions, genealogy, separated families

  2. reference samples: coronial cases like MPI and DVI

  3. criminal cases
• what is the relationship analysis based on

  genetic evidence of STR and LR
• what is a problem of relationship testing 


  sometimes siblings do not share the same alleles
• what is the limit when it comes to family

  • limit is 2nd cousins and grandparents
• what do small communities =

  it causes people to share the same alleles
• 2 theta outcomes 


  IBD: identical by descent: 2 people have common ancestor

  IBS: identical by state: 2 people have indentical alleles by chance through mutations
• what is common in kinship testing

  for individuals that cannot be excluded from a claimed relationship due to allele sharing
• kinship equation 


  RI-LR =x/y
• RI-LR vs CRI


  RI-LR: calculated for each indiv locus

  CRI: combined relationship index, calculated by x RI-LR for all independent loci
• what does RI-LR take into account and does not take into account

  into account

  • prob of allele sharing
  • allele freq
  • possible mutation events

  not into account:

  • non genetic evidence like prior probability
• prior probability 


  estimate of the prob prior to considering genetic evidence
• 50% prior prob

  • plaintiff and defence stories are equally plausible
• what does the AAPB recommend for MPI

  using 1/N
• what does kinship suggest 


  it suggests that individuals cannot be excluded due to allele sharing
• degree of relationships 


  full sibs: 25% for 2 and 0 alleles and 50% for 1 allele

  parent: 100% for 1 allele

  HS, grandparent, cousin, aunty/uncle: 50% for either 1 or 0 alleles

  1st cousins: 25% for 1 allele and 75% for 0 alleles

  unrelated: 100% for 0 alleles
• misleading stats 


  99% = 1 out of 100

  99.9% = 1 out of 1,000

  99.99% = 1 out of 10,000

  99.999% = 1 out of 100,000
• uncertainty 


  increase in kinship due to variation in inheritance patterns and due to pro of presence of shared alleles with unrelated
• 5 possible relationships b/w suspect and true prep

  1. committed crime
  2. siblings did
  3. relative did
  4. racial group did
  5. outside racial group
• match prob 


  sib: 1 in 10,000

  parent: 1 in 1 million

  hs, uncle or nephew: 1 in 10 million

  1st cousin: 1 in 100 million

  unrelated: 1 in 1 billion
• 20 STR are


  inconclusive especially for ID of distant relatives