Biotechnology

1. Biotechnology

2. Two decades of DNA fingerprints • Sir Alec's breakthrough has transformed crime investigations • Scientists in Leicester are marking the 20th anniversary of the invention of genetic fingerprinting. • The breakthrough was made accidentally by Professor Sir Alec Jeffreys at the city's university on 10 September 1984. • Since then, the technique has been used to trap criminals, identify victims of war, settle paternity disputes, and prove the claims of clones like Dolly. • It has also led to a national database in the UK of 2.5 million genetic profiles, mainly from convicted criminals but also from unsolved casework. • It is a development Sir Alec has some qualms about, and he opposes the practice, approved by a court in 2002, of retaining DNA samples from suspects who are acquitted. • "My view is, that is discriminatory," he said. "It works on a premise that the suspect population, even if innocent, is more likely to offend in the future."

3. Two decades of DNA fingerprints • He would prefer to see a database that included all individuals, with strict guidelines on what information could be stored. The professor would not allow sensitive personal details such as a person's medical history or ethnic origin to be mined from the data. • 'Fantasy' vision • Sir Alec refers to the time when his lab stumbled across the technique as a "eureka moment". • He and colleagues had been studying genetic variation and how it might be used to track hereditary disease through families.

4. The double-stranded DNA molecule lies at the heart of nearly all our cells • Chemical components called bases - adenine (A), thymine (T), cytosine(C) and guanine (G) - spell out a profile unique to the individual • DNA fingerprinting looks for patterns in what appear to be random repeats in this code • Enzymes chop up a sample of DNA, with the fragments sorted according to size • Further processing with X-ray film produces a characteristic barcode • If two barcodes from two different samples match, they probably come from the same source • "That magic moment was on a Monday morning 20 years ago, when I pulled that grubby bit of X-ray film out of the developing tank and saw these fuzzy but extraordinarily variable patterns of DNA," he explained to the BBC. • "The penny dropped pretty well immediately; we could see the potential for individual identification." • Within a year, it had been used in a Leicestershire double-rape-and-murder case, to prove one man could not have committed the crimes and to confirm another had. • Indeed, it is in the area of criminal investigation that DNA fingerprinting has had its most profound impact. • Sir Alec recalls: "Not so long ago I was very kindly invited down to the Old Bailey, to have lunch with some of the judges there and sat opposite a judge who was very excited because he was trying a case at the Old Bailey that didn't have any DNA evidence." • Since the DNA profiling discovery in 1984, Sir Alec has won world acclaim for his work. • In April this year, he won the Louis-Jeantet Prize for Medicine, which is awarded to scientists who are distinguished for the highest quality of biomedical research in Europe. • "If you had told me that 20 years later this technology would directly touch the lives of 10 million people worldwide, I would have thought 'fantasy, no way'; I am amazed."

5. Profiling Techniques • DNA Profiling / Fingerprinting: DNA is cut, by special enzymes, at specific base sequences which will indefinitely vary from person to person. • These cut strands are then run through electrophoresis gel and can be compared with the DNA from other sources. If they match they are the same DNA. Genetic probes • Genetic probe/gene probe: a fragment of DNA or RNA labelled with radioactive isotopes / fluorescent markers to aid in the identification of specific sequence of bases. • The fragment is added to the denatured DNA and if it combines then it will be identifiable in the chromosome later.

6. Polymerase chain reaction (PCR) • Segments of DNA are artificially multiplied using DNA polymerase (generally Taq polymerase from the Thermusaquaticus bacteria) and primers (which get process started) • DNA is denatured (by heat) so it splits • Then the primers are added which provides a starting point for the process (on both strands) • Polymerase causes reproduction of strand • The process continues on the products of the 1st PCR (more primer and polymerase are added each time) but the strand becomes more precise.

8. Genetic Engineering (Recombinant DNA Technology) • Introduction of foreign or modified DNA into an organism • Transgenic organisms: genome altered by additional genes • Generally the purpose in not to make copies of a gene but to give the vector the gene to produce something else (eg. Insulin or hGH) • Plasmids: are circular double stranded units of cytoplasmic DNA (can replicate in a cell independantly of chromosomal DNA) • Restriction enzyme: enzyme which cuts strands of DNA at specific nucleotide sequences (usually with ‘sticky ends’)

10. Insulin • Initially obtained from pancreas of pigs and cattle • hGH • Initially obtained from anterior pituitary gland of deceased people. • Factor VIII • Haemophilia is caused by a disorder in a blood clotting protein known as factor VIII • Factor VIII was originally obtained from the plasma of donors but as a result, infections of HIV and Hrp C were abundant. • Recombinant Factor 8 has solved many problems. • Vaccines • E.g Hep B vaccine

11. Gene Therapy • Replacement of a faulty gene with a healthy one • E.g. Cystic fibrosis: • Affects mainly lungs and pancreas causing excess mucus production which may trap bacteria in the lungs causing infection.  lung damage, decreased life expectancy • Also affects secretion of digestive enzymes • Mutations in CFTR gene (Cystic Fibrosis transmembrane regulator) cause Cystic fibrosis • By adding normal copies of gene the mutations don’t occur. (unfortunately when new cells die they are replaced by fautly ones- approx every 120 days) • Delivered by fat capsules, nose drops, synthetic vectors, possibly aerosol. • E.g. Huntingtons disease • Mutated protein (called huntingtin) results in brain nerve cells being damaged • Results in flailing limbs and eventual dementia • Possible gene therapy to introduce a corrective gene which boosts a natural shield against effects of defective huntingtin.

12. Cell replacement therapy • The process of replacing defective cells with new stem cells Tissue Engineering • Process of restoring healthy organs by replacing defective tissues • The tissue is grown from stem cells which attach to a ‘scaffold’ (natural or artificial biodegradable, poreous, structure which will allow tissue to form around it)