Dna Analysis Essay

It is common to hear reports in the media of crimes that have been solved with theassistance of DNA analysis (Brown, 2006). If enough blood, semen or tissue is foundat a crime scene, forensic laboratories can determine the blood type or tissue type byusing antibodies to detect specific cell surface proteins (Campbell et al, 2006). Thismethod unfortunately requires large amounts of fresh samples and is not a strongsource of evidence as several people have the same blood or tissue type and thus itonly narrows down a few suspects (Campbell et al, 2006). DNA testing has a highlevel of certainty as DNA sequencing is unique for each individual except for identical twins (Campbell et al, 2006).To obtain a profile a Short Tandem Repeat (STR) needs to be generated from blood or other samples (Bustamante et al, 2007). Profiling makes use of the STRs which areshort sequences, 1-13 nucleotides long that are repeated several times in tandem array.In DNA profiling, the alleles of a selected number of different STRs are determined(Brown, 2006).When restriction enzymes are used to cut STRs and the results areanalysed (by electrophoresis or southern blotting a technique not investigated in thisexperiement), a pattern of bands are produced which is described as a ‘DNAfingerprint’ as it is unique for each individual (Cummings, 2003).DNA-modifying enzymes that cut DNA at specific sequences produce DNA segmentswhich are called restriction endonucleases or …show more content…
Many proteins or nucleic acids have very similar charge to mass ratio andelectrophoresis of these macromolecules results in little or no separation of moleculesof different lengths, thus successful separation of proteins can be carried out invarious gels rather than in a liquid solution (Lodish et al., 2004). In this experiment,we will only use restriction enzymes and agarose gel electrophoresis techniques for our crime