DNA profiling
- Created by: meganjayne15
- Created on: 01-05-14 20:31
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- DNA Profiling
- process
- 1. Sample collection
- crime scene
- swab
- freeze
- double swabbing (wet/dry)
- submit both to lab - doubles the amount of DNA
- mini taping
- swab
- evidence clothing
- 0.5cm x 0.5cm
- cellular
- control DNA samples
- buccal scrape
- crime scene
- 2. DNA extraction
- separates DNA from other source
- several methods
- organic extraction
- phenol-chloroform
- chelex extraction
- 5% chelex beads
- qiagen extraction
- spin column technology
- organic extraction
- several methods
- separates DNA from other source
- 3. DNA quantification (optional)
- optimum quantity is less than 1 nanograms
- techniques
- 260nm absorbance
- ethidium-broide plate fluorescence
- slot-blot procedure
- SYBR green
- techniques
- optimum quantity is less than 1 nanograms
- 4. PCR amplification
- allows short stretch of DNA to be amplified
- samples are heated to 94C to denature (seperate the single strands) the target DNA
- temp lowered to allow the left and right primers to anneal (base pair) to their complementary sequences. the primers are designed to bracket the DNA region to be amplified.
- temp raised to 72C which allows the polymerase to bind to each primed site and extend a new DNA strand
- procedure repeats
- 1 strand turns to 2 - 2 strands turn to 4 - 4 strands turn to 8 etc
- procedure repeats
- temp raised to 72C which allows the polymerase to bind to each primed site and extend a new DNA strand
- temp lowered to allow the left and right primers to anneal (base pair) to their complementary sequences. the primers are designed to bracket the DNA region to be amplified.
- samples are heated to 94C to denature (seperate the single strands) the target DNA
- allows short stretch of DNA to be amplified
- 5. capillary electrophoresis - seperate out
- separation according to size
- small molecules travel fastest
- separation according to size
- 6. electropherogram analysis - graph
- male - two peaks
- female - one peak
- 1. Sample collection
- PED
- Police Elimination Database
- any police professional is entered on to it
- NDNAD
- National DNA Database
- owned by NCA - national crime agency
- DNA profiles stored onto NDNAD
- adults - convicted - indefinite
- adults - arrested but not convicted - 6 years
- under 18 - convicted of a serious offence or more than one minor offence - indefinite
- under 18 - single minor offence - 5 years
- 16 & 17 - arrested but not convicted - 6 years
- all other under 18 - arrested but not convicted - 3 years
- National DNA Database
- what is it?
- polymerase chain reaction - photocopy DNA
- uses STR (short tandem repeats)
- reduction in analysis time
- crime scene samples
- single hair
- fingerprints
- single blood spot
- fingernail scrapings
- DNA inheritance
- inherited from parents
- relatives are more likely to have similar characteristics of DNA
- two possibilities
- sibling of offender
- parent or child of offender
- basic principles
- twenty alleles
- ten from mother and ten from father
- very expensive
- has been used to convict
- close matches
- twenty alleles
- inherited from parents
- mtDNA
- mitochondrial DNA
- from mother
- cannot distinguish individual
- no nucleus present
- cannot distinguish individual
- from mother
- used for skeletal remains
- mitochondrial DNA
- Y-STR analysis
- y chromosome only (males)
- used in sexual offences cases and paternity cases
- high number of markers needed
- process
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