Y-STR Profiling

• Explain Y-chromosomes “Y-CHR”

  • linage marker
  • passed down from father to son without changes
  • referred to as haplotypes which is a single allele per indiv
• describe the structure of Y-chr

  • length is approx. 60 million nucleotides
  • tips are called: pseudoautosomal regions “PAR”
  • 95% are non-recombining protion of Y: NR
• In the non-recombining area Of the Y-chr

  There is male specific region of the Y chromo: MSY
• MSY


  is composed of:

  1. euchromatic: functional genes
  2. heterochromatic: lack genes
• euchromatic

  • functional gene
  • 1/3 size
  • codes for proteins <— where SRY is located
• heterichromatic 


  lacks genes
• what is the function of SRY

  Determine maleness due to testiest terminate factor: TTF
• what is the outcome if there is a defect in the SRY

  it affects the embryo
• how can one track male genetic pedigrees

  • through genetic polymorphisms <- STR/SNPalong NRY
• explain the structure of CHR Y

  • 1/3 length of x chromo
  • conatins telemeres: pseudo-auto region
  • b/w 2 telomeres is MSY
• what regions are important in sex development

  • A2F a,b and c <— azosperma factor
• define Y-STR


  short tandem repeat on Y chromo

  linegage marker: haplot type
• do all generations have the same Y-chromo

  no for 2 reasons

  1. mutation
  2. lineage could be stop due to no inheritance of Y chromo and thus a different lineage could occur due to the husband
• compare DYS389II and DYS3891

  II: is full length of the marker

  I: is the partial length of the maker
• why do we use Y-chromo

  1. applications: forensic, genealogical and evolutionary
  2. advantages to Human ID test
  3. needs
• compare single and multicopy Y-STR markers

  Single: only at 1 specific locus, when amplified with primer = single PCR product and EPGs show a single peaks per locus

  multi: more than 1 allele at locus, occurs due to duplication in plaindomic dyes, produces more than 1 PCR product and shows more than 1 peak
• other multi-copy Y-STR

  1. YCA 11A/B
  2. DYS464 a—>d
  3. DYS389 I/II
• what is found in multiplex 12 multi copy Y-STR

  1. 12 multicopy Y-STR
  2. a single copy Y-STR
  3. ameloginin
• compare PP21 and Yfiler

  pp21: detected 5 regions and 12 markers
• why is schematic of loci NIST Y STR 20-ex important

  cause it contains ruoprean extended haplotypes
• Advnatges of Y-STR 20 plex

  1. single amplification of extended haplotype
  2. sensitive to <500pg with 28 cycle PCR
  3. male specific with > 100x female DNA
  4. 10 loci amplifies with less than 200bp in size <— aids with degreaded DNA
• what is the power of discrimination for

  1. NIST Y STR 20 PLEX: 1:1,00
  2. Y-filer <— 98%
• list the application of Y-STR testing

  • used for most sexual assaults
  • used for mutli, male associations and helps with separate mixture
• challenges of Y-STR profiling

  1. degraded DNA
  2. inhibitors
• when do you request Y-STR testing

  1. When female DNA is abundant
  2. in FMEK swabs
  3. blood or saliva swabs <— where there is a absences of sperm that prevents successful differential extraction
  4. mixtures
  5. determine number of male contributors
  6. degraded DNA
• 3 possibilities

  1. exclesion: does not originate from the source
  2. inconclusive: insufficient data
  3. inclusion/ failure to exclude: could originate from the same soruce and where stat calculation occurs
• sampling correction 


  Used in conjunction with counting methods
• the stat calcualtion to use for y-str

  COUNTING METHOD which is the number of haplotypes observed in a database
• compare matching profiles with autosomal and Y-STR

  auto: independence b/w lo I, multi genotypes, product rule of match prop and high discrimination power

  Y-str: NO independence, single haplotype, haplotype freak and low dicmrination
• challenges of Y-STR


  low discrimination power = lab to limit their interpretation of mixed Y-STR profiles up to 3 people for a major and 2 for a minor
• semen can be affected by

  1. drainage
  2. dilution
  3. degradation
• Y-STR profiles only last

  less than 6 days