Although routine DNA sequencing in the doctor's office is still many years away, some large medical centers have begun to use sequencing to detect and treat some diseases. In cancer, for example, physicians are increasingly able to use sequence data to identify the particular type of cancer a patient has.
This enables the physician to make better choices for treatments. Other researchers are studying its use in screening newborns for disease and disease risk. Another National Institutes of Health program examines how gene activity is controlled in different tissues and the role of gene regulation in disease.
Ongoing and planned large-scale projects use DNA sequencing to examine the development of common and complex diseases, such as heart disease and diabetes, and in inherited diseases that cause physical malformations, developmental delay and metabolic diseases. Comparing the genome sequences of different types of animals and organisms, such as chimpanzees and yeast, can also provide insights into the biology of development and evolution.
What is DNA sequencing? How new is DNA sequencing? What new sequencing methods have been developed? Are newer sequencing technologies under development?
This provided a breakthrough in the sequencing of long stretches of DNA in terms of speed and accuracy and laid the foundation for the Human Genome Project. He was also instrumental in the application of genetic engineering to agricultural plants to improve their output and resistance to pests, salt and drought.
He shared the Nobel Prize in for helping to discover restriction enzymes and showing their application in molecular genetics. It was based on some work he carried out in the s. Arber indicated in that restriction enzymes could be used as a tool for cleaving DNA. The enzymes are now an important tool for genetic engineering. In she completed the sequence of the poliovirus, the longest piece of eukaryotic DNA to be sequenced at that time. She devoted her life to understanding the Epstein-Barr virus, the cause of Burkitt's Lymphoma, a deadly form of cancer.
This he achieved with Kent Wilcox in Smith was awarded the Nobel Prize for Physiology or Medicine in for his part in the discovery of the enzyme. It was the first bacterial genome to be deciphered. Later on he helped in the genomic sequencing efforts for the fruit fly and humans at Celera Genomics. He was involved in some of the early efforts to pioneer techniques for determining base sequences in nucleic acids, known known as DNA sequencing, for which he shared the Nobel Prize for Chemistry in He was the first scientist to propose the existence of intron and exons.
In Gilbert became a proponent of the theory that the first forms of life evolved out of replicating RNA molecules. The same year he began campaigning to set up the Human Genome Project.
He was also a co-founder and the first Chief Executive Officer of Biogen, a biotechnology company originally set up to commercialise genetic engineering. Thesis: 'On the metabolism of the amino acid lysine in the animal body'. It was the first animal to have its genome sequenced.
Based on his work with the nematode, Sulston helped set up the project to sequence the human genome which he did as director of the Sanger Centre. The first draft of the human genome sequence was completed in In he shared the Nobel Prize for identifying how genes regulate the life cycle of cells through apoptosis.
His work is initially supported by a Beit Memorial Fellowship from and then by Medical Research Council from In Venter worked with a team to create the first form of synthetic life.
This involved synthesising a long molecule of DNA that contained an entire bacerum genome and then inserting this into another cell. The technique Sanger develops for sequencing insulin later becomes known as the degradation or DNP method. It was the result of a collective effort led by Margaret Dayhoff to co-ordinate the ever-growing amount of information about protein sequences and their biochemical function.
It provided the model for GenBank and many other molecular databases. Arber, 'Host-controlled modification of bacteriophage', Annual Review Microbiology, 19 , They found that bacteria protect themselves against invading viruses by producing two types of enzymes.
One cut up the DNA of the virus and the other restricted its growth. Arber believed these two enzymes could provide an important tool for cutting and pasting DNA, the method now used in genetic engineering. Taq is later important in the PCR technique. Restriction enzymes are now workhorses of molecular biology. They are essential in the development of recombinant DNA and were pivotal to the foundation of the biotechnology industry.
The method provides an artificial system of primers and templates that allows DNA polymerase to copy segments of the gene being synthesised. Represents radical new approach which allows direct visual scanning of a sequence. It is the first DNA based organism to have its complete genome sequenced. Sanger and his team use the plus and minus technique to determine the sequence. The first, known as the Sanger Method, or dideoxy sequencing, involves the breaking down and then building up of DNA sequences.
The second, the Maxam-Gilbert method, involves the partial chemical modification of nucleotides in DNA. Arber was the first to discover the enzymes; Smitth demonstrated their capacity to cut DNA at specific sites and Nathans showed how they could be used to construct genetic maps. With their ability to cut DNA into defined fragments restriction enzymes paved the way to the development of genetic engineering.
Awarded on the basis of their 'contributions concerning the determination of base sequences in nucleic acids. It was one of the largest tracts of eukaryotic DNA sequenced up to this time. Within a month of its operation more than scientists had requested access to the database. The clones are then sequenced at random and the results assembled by computer which compares all of the sequence reads and aligns the matching sequences to produce the complete genome sequence.
It was to serve as a repository for newly determined sequences, as a tool for sequencers assembling genomes and for bioinformatic researchers. PCR uses heat and enzymes to make unlimited copies of genes and gene fragments.
He developed the technique as part of his efforts to trace genes through family lineages. It was based on his discovery that each individual had unique numbers of repeated DNA fragments, called restriction fragment length polymorphisms, in their cells. The test proved the boy was related to his mother.
Without the test the mother and son would not have been able to remain together in the same country. The machine is commercialised by Applied Biosystems. Many scientists were highly sceptical that such a project was feasible because of the large size of the genome and the time and costs involved. The human genome was 10, bigger in size. This is now a common tool for bioinformatics. It allos for the comparison and aligning of sequences.
Its aim was to determine the sequence of chemical base pairs which make up DNA, and to identify and map approximately 20, to 25, genes of the human genome. This was a major breakthrough as prior to this most scientists were sceptical of the role played between genetics and complex human disease. Frommer, L. McDonald, D. Millar, C. Collis, F.
Watt, G. Grigg, P. Molloy, C. It incorporated two different techniques proposed by David Deamer and Georges Church. The marchinery and reagents involved in the method was first commercialised by Pyrosequencing AB. Celera's entry into the field pose policy concerns about open access to gene sequencing data and accelerates the sequencing process in the Human Genome Project. The sequence was published in ST Cole et al 'Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence', Nature, , By sequencing the genome of the bacteria scientists hoped to improve knowledge about its biology and to improve therapeutics against tuberculosis, a disease that continues to be a serious challenge in global health.
The genome is made up of 1. The sequence was found to follow those of viruses, several bacteria and a yeast. The project was initiated with the development of a clone-based physical map which was important for undertaking the molecular analysis of genes.
The human genome is now know to have more than 3 billion DNA base pairs. Overall the Human Genome Project took 13 years to complete and cost approximate 50 billion dollars. Findings from the work have allowed researchers to begin to understand the function of genes and proteins and their relationship with disease. They sequenced the DNA of Arabidopsis thaliana, a flowering weed in the mustard family. The sequenced genome contains 25, genes encoding proteins from 11, families.
The project took 4 years to complete. It was shown to have a 2. Their work was first announced online in 'Chemical synthesis of poliovirus cDNA: Generation of infectious virus in the absence of natural template', Nature, 12 July , doi Most of the government-sponsored sequencing was performed in universities and research centres from the United States, the United Kingdom, Japan, France, Germany.
Used to measure the expression of large numbers of genes simultaneously or to genotype multiple regions of a genome, microarray chips are now used for a wide number of clinical applications. This is designed to find the specific gene types of a patient to work out how they will metabolise certain medicines so as to guide what treatment and dose should be prescribed. Sequence of the last chromosome in the Human Genome Project is published in Nature. Overall the project characterised microbiota from healthy individuals from 5 different sites: nasal passages, oral cavity, skin, gastrointestinal tract, and urogenital tract.
It focused on two disorders of increasing importance in Europe - inflammatory bowel disease and obesity. Prospective sequencing then led them to screen staff and identify the potential source of infection. The researchers reported that the cost of DNA sequencing for the infection was half of the 10, pounds spent by the hospital to combat the outbreak of MRSA.
It was investigated using blood samples from patients with stage 2 and 3 melanoma who had received surgery. Based on his work with the nematode Sulston helped set up the project to sequence the human genome which he did as director of the Sanger Centre.
Sulston shared the Nobel Prize in for identifying how genes regulate the life cycle of cells through apoptosis. A trial supported by the National Cancer Institute with 10, patients with the most common forms of breast cancer, showed that the test was highly accurate in determining which women would benefit most from chemotherapy after an operation to remove the cancer and who could be safely spared such treatment. Results from the trial, presented to the American Society of Clinical Oncology in California in Chicago, were described by doctors as 'practice changing'.
The trial's results were published in JA Sparano, et al, 'Adjuvant chemotherapy guided by a gene expression assay in breast cancer', New England Journal of Medicine, July 12 , Overall 15, cancer patients had their DNA analysed, half of whom went on to take part in a clinical trial or receive targeted treatment.
One in four participants with rare diseases who had their genomes sequenced received a diagnosis for the first time, thereby paving the way to getting effective treatment. All the sequencing was carried out by the Wellcome Sanger Institute, near Cambridge, in laboratories run by Illumina, a Californian biotechnology company. The test was developed by South West Genomic Laboratory Hub and enable quick diagnoses of approximately 5, rare conditions like cystic fibrosis.
Frederick Sanger, twice Nobel Prize winner, born. Ray Wu was born in Beijing, China. To run the machine, a technician pours gel into the space between two glass plates set less than half a millimeter two-hundredths of an inch apart. As the DNA pieces move through the gel, the sequencing machine reads the order of DNA bases and stores this information in its computer memory. But just like the slab-gel machines, capillary machines read the base sequence as DNA moves through the gel.
Capillary sequencers can sequence each piece of DNA about twice as fast as slab-gel machines. Most large-scale sequencing projects use a combination of slab-gel and capillary machines. Sequencing machines can't "see" DNA directly, so scientists must use a complex set of procedures to prepare DNA for sequencing.
When DNA is finally in a form that the machines can read, it has been chopped up, copied, chemically modified, and tagged with fluorescent dyes corresponding to the four different DNA bases, or genetic letters. Before it is sequenced, a piece of DNA is copied many times, then divided into four batches in preparation for another round of copying.
When one of these modified bases is incorporated into a DNA molecule, the chain of bases stops growing. The result of all this is that one batch of DNA will contain only pieces that end in T, another only pieces that end in A, a third only pieces that end in G, and the fourth batch only pieces that end in C.
In the second round of copying, a different fluorescent dye is also added to each batch of DNA. Thus, every piece of DNA that ends with T has a blue dye tag, for example; those that end in A have a red dye tag; those that end in G have a yellow dye tag; and those that end in C have a green dye tag. At the end of the second round of copying, each batch will contain the following pieces of DNA:.
Into one lane or capillary of a sequencing machine goes a mixture of DNA from all four batches. Thus, in this example, the first piece to make it all the way through the gel is a T attached to a blue dye tag; the next piece is TA with a red dye tag; next is TAG attached to a yellow dye tag; and so on. As the pieces emerge from the gel, they move past a laser that causes the dye molecules to fluoresce. In this way, the sequence grows base by base. Each sequence of bases or so that a sequencing machine generates is known as a "read.
An automatic sequencing machine spits out what genome scientists call "raw" sequence. In raw sequence, the reads or short DNA sequences are all jumbled together, like the pieces of a jigsaw puzzle in a just-opened box.
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