DNA+forensics

It used to be that fingerprinting was the most accurate way to place a suspect at a crime. Now there is DNA testing.

DNA testing • Takes several weeks because it is highly affective in matching base pair sequences o Makes DNA tests the most accurate piece of evidence a lawyer can have • Two samples are taken, one from suspect, and one from the scene of the crime • First used in the 1980’s in a case involving a man that impregnated his daughter

• Two different types o RFLP- restriction fragment length polymorphism • More accurate • Examines sequences of a base pair in a DNA strand • Requires many sample cells that are “fresh” • Take from three weeks to three months to complete o PCR- polymerase chain reaction test • Takes a week at most to conduct • DNA sample can be minute and does not have to be fresh • Copying the available DNA, and using only one specific gene- the HLA DQ alpha • Tests alleles to determine matches • Test is inconclusive because many people can have the same allele • “single locus DNA fingerprinting” • Electrophoresis is involved - amplification- the amplification process can be limited to specific areas of the sequence

DNA- genetic instructions DNA the same no matter what type of cell Mitochondrial DNA comes from mother DNA is set on the chromosomes PCR makes copies

Types of objects where DNA can be found - blood stains - semen stains - chewing gum - stamps and envelopes - penile swabs - plant material - sweaty clothing - bone - hair - fingernail scrapings - saliva - animal material

Isolation of DNA--> chemical things, heating-->DNA Amplification (making copies)- 28 cycles- billions of copies Step one: Denature through heat- (a lot of heat) Step two: Anneal- add enzyme and random DNA base pairs Step three- Copying and extending the DNA Analysis on amplified DNA