DNA profiling Flashcards

1
Q

Who discovered DNA profiling?

A

Sir Alex Jeffreys 1984

whilst looking at genetic variation in disease

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2
Q

First use?

A

In the conviction of Colin Pitchfork 1987

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3
Q

DNA sources

A

blood, bones, teeth, tissues, semen, urine, hair, saliva

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4
Q

RFLP - Restriction Fragment Length Polymorphism

A
  • uses restriction enzymes to cut DNA
  • variable number of tandem repeats
  • large amounts of DNA required
  • requires undegraded material
  • warm/moist conditions increase degradation
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5
Q

PCR- Polymerase Chain Reaction

A

Short tandem repeats

  • less DNA required
  • can be partially degraded and still build profile
  • limitations? - contamination
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6
Q

PCR

A
  • Used to make lots of copies of specific sections of DNA -STRs
  • One cycle of PCR goes through a series of temp changes
  • Amplifies DNA copies
  • These copies then analysed using gel electrophoresis - separated according to size
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7
Q

STR-Short tandem repeats

A

DNA has variety of STRs

  • people vary in n.o. of repeats at STR loci
  • Use PCR - recognise constant conserved sequences
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8
Q

SNPs

A
  • Single nucleotide polymorphisms

- differences in a single base unit

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9
Q

Stutter bands

A

DNA repeats slipping out of register during PCR
Usually 1 repeat length smaller than the main band
mechanism= Deletion caused by forward slippage

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10
Q

Partial profiles

A
  • used for familial searching
  • prioritise using specific parameters
  • can use low copy number profiling
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11
Q

LCN - low copy number

A
  • copy 10 informative sites from smaller amount of starting material
  • takes longer to process
  • used in familial searching
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12
Q

Mitochondrial DNA

A
  • 1mitochondrion has 5-10 identical circular molecules of DNA
  • each has 37 genes
  • useful in mass disasters to link family members
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13
Q

Y Chromosome STR testing

A
  • amelogenin locus and/or

- STRs on Y chromosome

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14
Q

% of population with their profile on the DNA database

A

UK-5.2%

USA -0.5%

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15
Q

Probability that someone would match random DNA sample…

A

3 sites = 1/1000

13 (CODIS) = 1 in ten trillion

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16
Q

Exlusion

A

non-match

17
Q

Inclusion

A

match

18
Q

Low Copy Number LCN

A
  • very few cells
  • international cases
  • skin, sweat in fingerprints
  • takes longer
  • cold cases
19
Q

Familial searching

A
  • full DNA profile
  • no matches on DNA database
  • similar DNA within family group
20
Q

M3 Murder (2003)

A

Craig harmen, DNA on brick

21
Q

Cold cases

A

DNA boost (Computer -based analysis system to interpret mixtures)

22
Q

Issues to consider

A
  • contamination
  • changes in guidelines
  • continuity of evidence
  • storage of material
23
Q

First use of Familial Search -cold case

A

Dec. 2001 -Joseph Kappen match for DNA found on profiles on cold murder case

24
Q

Paternity

A

child has two alleles
mitochondrial dna from mother
Y chromosome (if boy) from father

25
Q

Using DNA profiling for identification: Bosnia

A

Former Yugoslavia -est. 30/40,000 bodies

  • blood and bone samples
  • profiles of bodies compared with those of living relatives
  • difficulties -a)whole families killed
    b) Bones scattered
26
Q

9/11 2001

A
  • 3000 deaths
  • new extraction methods from bone
  • mini STRs
  • SNPs
  • Mt DNA
27
Q

Genetic diseases

A
  • current standard forensic DNA tests do not look at genes
  • mutations in genes can lead to defects
  • denetic diversity–> polymorphism
  • mutations within restriction sites changes the sizes of fragments
  • detect genetic diseases by RFLP or PCR
28
Q

Modern use of Y-STR testing

A

Sadaam Hussein (confirmed his identity by matching Y-STR Halotype to sons)