27 YEARS ON, BREAKTHROUGH FOR COPS IN SEARCH FOR SERIAL BEAST: How DNA tests work.DEOXYRIBONUCLEIC acid (DNA DNA: see nucleic acid. DNA or deoxyribonucleic acid One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. ) is found in all our cells. It can be extracted from blood, hair, saliva, teeth, sweat and semen semen or seminal fluid Whitish viscous fluid emitted from the male reproductive tract that contains sperm and liquids (seminal plasma) that help keep them viable. . The chemical structure of everyone's DNA is the same what differs is the order of nucleotides,a pair of which are contained in every cell. One is inherited from your father,one from your mother. Scientists compare DNA samples by looking at repeating patterns of these pairs. These do not give a unique 'fingerprint' but can determine whether two DNA samples are from the same person or a relative. Dr Darren Monckton of Glasgow University's Molecular Genetics molecular genetics n. The branch of genetics that deals with hereditary transmission and variation on the molecular level. Department said: 'Only one per cent of DNA differs from one individual to another. 'Police check 10 genetic markers. If a match, the chances of the two samples not coming from the same person is one in ten million.' CAPTION(S): EXPERT: Dr Monckton |
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