11/7/2023 0 Comments Gene sequence definitionThese were built following the introduction of microfluidic separation devices which improved sample injection and speeded up separation times. Several new DNA sequencing methods and machines have been developed since the 1990s. These machines used capillary electrophoresis rather than gel electrophoresis using slabs. The first automated DNA sequencer was devised in 1986 by Leroy Hood and colleagues at the California Institute of Technology together with a team including Lloyd Smith and Michael and Tim Hunkapiller. It was also amenable to automation, paving the way to the first generation of automated DNA sequencers. By contrast, the Sanger method gained popularity because it was easier to use and more reliable. Added to this, the method it was difficult to scale-up and could not be used in standard molecular biology kits because of its technical complexity. While the Maxam-Gilbert method initially proved the most popular, it soon fell out of favour because it necessitated the use of hazardous chemicals and radioisotopes. Their approach appeared alongside the reporting of another technique by Allan Maxam and Walter Gilbert at Harvard University. This made it possible to sequence much longer stretches of DNA very rapidly. Three years later, in 1977, Sanger and his colleagues announced another technique called the 'Sanger method' or 'dideoxy sequencing'. This enabled the sequencing of up to 80 nucleotides in one go. In 1975 Sanger, together with Alan Coulson, published what became known as the 'Plus and Minus' technique. Over the course of the 1970s Wu's method was modified by Fred Sanger at the Laboratory of Molecular Biology in Cambridge, UK. Subsequently, in 1971, Wu demonstrated his method could sequence the ends of DNA in lambda phage, and two years later that it had the capacity to determine the sequence of any DNA. Critically, Wu's approach broke the DNA sequence down into several different components for analysis, thereby circumventing the need for large quantities of homogeneous DNA. Using highly labelled deoxynucleotides (single units of DNA) and DNA polymerase he found a way to sequence the terminal region of a DNA molecule. Ray Wu, a Chinese American biologist based at Cornell University, published one of the first methods for sequencing DNA in 1970. Scientists also lacked the means to degrade DNA which they needed for sequence analysis.Ī new chapter opened up in the 1960s with the emergence of techniques to sequence ribonucleic acid (RNA)s. In part this reflected the fact that small DNA molecules contain several thousands of nucleotides and it was difficult to obtain large quantities of homogeneous DNA. Drug developers are also using pharmacogenomic data to design drugs which can be targeted at subgroups of patients with specific genetic profiles.Īlthough scientists established DNA had a double helix structure in 1953, it was to be many more years before they could analyse DNA fragments. Individual genetic profiling is already being used routinely to prescribe therapies for patients with HIV, breast cancer, lymphoblastic leukaemia and colon cancer and in the future will be used to tailor treatments for cardiovascular disease, cancer, asthma, Alzheimer's disease and depression. Such labelling is not only important in terms of matching patients to their most appropriate drug, but also for working out what their drug dose should be and their level of risk in terms of adverse events. Over 140 drugs approved by the FDA now include pharmacogenomic information in their labelling. Such data is being used to determine which drug gives the best outcome in particular patients. Pharmacogenomics looks at how a person's individual genome variations affect their response to a drug. This is a relatively new field which is leading the way to more personalised medicine. It has for example provided an important tool for determining the thousands of nucleotide variations associated with specific genetic diseases, like Huntington's, which may help to better understand these diseases and advance treatment.ĭNA sequencing also underpins pharmacogenomics. Connections Werner Arber | Exhibition: Fred Sanger ImportanceĭNA sequencing played a pivotal role in mapping out the human genome, completed in 2003, and is an essential tool for many basic and applied research applications today.
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