Garrod had studied medicine at Oxford University before following in his father's footsteps and becoming a physician. Whilst studying the human disorder alkaptonuria, he collected family history information from his patients. Through discussions with Mendelian advocate William Bateson, he concluded that alkaptonuria was a recessive disorder and, in , he published The Incidence of Alkaptonuria: A Study in Chemical Individuality.
Human Nucleotide Expansion Disorders (Nucleic Acids and Molecular Biology) - PDF Free Download
This was the first published account of recessive inheritance in humans. It was also the first time that a genetic disorder had been attributed to "inborn errors of metabolism", which referred to his belief that certain diseases were the result of errors or missing steps in the body's chemical pathways. These discoveries were some of the first milestones in scientists developing an understanding of the molecular basis of inheritance.
By the s, scientists understanding of the principles of inheritance had moved on considerably - genes were known to be the discrete units of heredity, as well as generating the enzymes which controlled metabolic functions. However, it wasn't until that deoxyribonucleic acid DNA was identified as the 'transforming principle'. The man who made the breakthrough was Oswald Avery, an immunochemist at the Hospital of the Rockefeller Institute for Medical Research. Avery had worked for many years with the bacterium responsible for pneumonia, pneumococcus, and had discovered that if a live but harmless form of pneumococcus was mixed with an inert but lethal form, the harmless bacteria would soon become deadly.
Determined to find out which substance was responsible for the transformation, he combined forces with Colin MacLeod and Maclyn McCarty and began to purify twenty gallons of bacteria. He soon noted that the substance did not seem to be a protein or carbohydrate but rather a nucleic acid, and with further analysis, it was revealed to be DNA.
In , after much deliberation, Avery and his colleagues published a paper in the Journal of Experimental Medicine, in which they outlined the nature of DNA as the 'transforming principle'. Although the paper was not widely read by geneticists at the time, it did inspire further research, paving the way for one of the biggest discoveries of the 20th century.
In , scientist Erwin Chargaff had read Oswald Avery's scientific paper , which identified DNA as the substance responsible for heredity. The paper had a huge impact on Chargaff and changed the future course of his career. I resolved to search for this text. Chargaff was determined to begin work on the chemistry of nucleic acids. His first move was to devise a method of analysing the nitrogenous components and sugars of DNA from different species.
Chargaff continued to improve his research methods and was eventually able to rapidly analyse DNA from a wide range of species. In , he summarised his two major findings regarding the chemistry of nucleic acids: first, that in any double-stranded DNA, the number of guanine units is equal to the number of cytosine units and the number of adenine units is equal to the number of thymine units, and second that the composition of DNA varies between species.
These discoveries are now known as 'Chargaff's Rules'. Rosalind Franklin was born in London in and conducted a large portion of the research which eventually led to the understanding of the structure of DNA - a major achievement at a time when only men were allowed in some universities' dining rooms.
After achieving a doctorate in physical chemistry from Cambridge University in , she spent three years at the Laboratoire Central des Services Chimiques de L'Etat in Paris, learning the X-Ray diffraction techniques that would make her name. Then, in , she returned to London to work as a research associate in John Randall's laboratory at King's College.
Franklin's role was to set up and improve the X-ray crystallography unit at King's College. She worked with the scientist Maurice Wilkins, and a student, Raymond Gosling, and was able to produce two sets of high-resolution photographs of DNA fibres. Using the photographs, she calculated the dimensions of the strands and also deduced that the phosphates were on the outside of what was probably a helical structure.
Franklin's photographs were described as, "the most beautiful X-ray photographs of any substance ever taken" by J.
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Bernal, and between and her research came close to discovering the structure of DNA. Unfortunately, she was ultimately beaten to the post by Thomas Watson and Frances Crick. Despite an age difference of 12 years, the pair immediately hit it off and Watson remained at the university to study the structure of DNA at Cavendish Laboratory. Using available X-ray data and model building, they were able to solve the puzzle that had baffled scientists for decades.
They published the now-famous paper in Nature in April, and in they were awarded the Nobel Prize for Physiology or Medicine along with Maurice Wilkins. Despite the fact that her photographs had been critical to Watson and Crick's solution, Rosalind Franklin was not honoured, as only three scientists could share the prize. She died in , after a short battle with cancer. Following Watson and Crick's discovery, scientists entered a period of frenzy, in which they rushed to be the first to decipher the genetic code. He handpicked 20 members - one for each amino acid - and they each wore a tie carrying the symbol of their allocated amino acid.
Ironically, the man who was to discover the genetic code, Marshall Nirenberg, was not a member. Today, scientists routinely use our growing understanding of genetics for disease diagnosis and prognosis. However, it took decades for cytogenetics the study of chromosomes to be recognised as a medical discipline.
Cytogenetics first had a major impact on disease diagnosis in , when an additional copy of chromosome 21 was linked to Down's syndrome.
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In the late s and early 70s, stains such as Giemsa were introduced, which bind to chromosomes in a non-uniform fashion, creating bands of light and dark areas. The invention transformed the discipline, making it possible to identify individual chromosomes, as well as sections within chromosomes, and formed the basis of early clinical genetic diagnosis.
DeWitt Stetten, Jr. He decided to focus his research on nucleic acids and protein synthesis in the hope of cracking 'life's code'. The following few years were taken up with experiments, as Nirenberg tried to show that RNA could trigger protein synthesis. By , Nirenberg and his post-doctoral fellow, Heinrich Matthaei were well on the way to solving the coding problem. Nirenberg and Matthaei ground up E. Coli bacteria cells, in order to rupture their walls and release the cytoplasm, which they then used in their experiments.
These experiments used 20 test tubes, each filled with a different amino acid - the scientists wanted to know which amino acid would be incorporated into a protein after the addition of a particular type of synthetic RNA.
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In , the pair performed an experiment which showed that a chain of the repeating bases uracil forced a protein chain made of one repeating amino acid, phenylalanine. This was a breakthrough experiment which proved that the code could be broken. Nirenberg and Matthaei conducted further experiments with other strands of synthetic RNA, before preparing papers for publication. However, there was still much work to do - the scientists now needed to determine which bases made up each codon, as well as the sequence of bases within the codons.
Around the same time, Nobel laureate Severo Ochoa was also working on the coding problem. This sparked intense competition between the laboratories, as the two scientists raced to be the first to the finish line. In the hope of ensuring that the first NIH scientist won the Nobel Prize, Nirenberg's colleagues put their own work on hold to help him achieve his goal. Finally, in , Nirenberg became the first person to sequence the code. In , his efforts were rewarded when he, Robert W. By the early s, molecular biologists had made incredible advances.
They could now decipher the genetic code and spell out the sequence of amino acids in proteins. However, further developments in the field were being held back by the inability to easily read the precise nucleotide sequences of DNA. In , Cambridge graduate Frederick Sanger started working for A. Chibnall , identifying the free amino groups in insulin. Through this work, he became the first person to order the amino acids and obtain a protein sequence, for which he later won a Nobel Prize. Each chromosome contains a single DNA molecule.
Humans have 23 pairs of chromosomes, which are found inside the cell's nucleus. But for many years, researchers did not realize the importance of this molecule. It was not until that James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin figured out the structure of DNA — a double helix — which they realized could carry biological information. DNA sequencing is technology that allows researchers to determine the order of bases in a DNA sequence. The technology can be used to determine the order of bases in genes, chromosomes, or an entire genome.
A person's DNA contains information about their heritage, and can sometimes reveal whether they are at risk for certain diseases. For instance, mutations in the BRCA1 and BRCA2 genes are known to increase the risk of breast and ovarian cancer, and analysis of these genes in a genetic test can reveal whether a person has these mutations. Until this time, the poliovirus could be grown only in the brains of chimpanzees or the spinal cords of monkeys.
Culturing cells on glass surfaces opened the way for diseases caused by viruses to be identified by their effects on cells cytopathogenic effect and by the presence of antibodies to them in the blood. Cell culture then led to the development and production of vaccines preparations used to elicit immunity against a disease such as the poliovirus vaccine. In the s the development of the electron microscope permitted individual virus particles to be seen for the first time, leading to the classification of viruses and giving insight into their structure.
Advancements that have been made in chemistry, physics, and molecular biology since the s have revolutionized the study of viruses. For example, electrophoresis on gel substrates gave a deeper understanding of the protein and nucleic acid composition of viruses. More-sophisticated immunologic procedures, including the use of monoclonal antibodies directed to specific antigenic sites on proteins, gave a better insight into the structure and function of viral proteins.
The progress made in the physics of crystals that could be studied by X-ray diffraction provided the high resolution required to discover the basic structure of minute viruses. Applications of new knowledge about cell biology and biochemistry helped to determine how viruses use their host cells for synthesizing viral nucleic acids and proteins.
EP1326971A2 - Proteins and nucleic acids encoding same - Google Patents
The revolution that took place in the field of molecular biology allowed the genetic information encoded in nucleic acids of viruses—which enables viruses to reproduce, synthesize unique proteins, and alter cellular functions—to be studied. In fact, the chemical and physical simplicity of viruses has made them an incisive experimental tool for probing the molecular events involved in certain life processes. Their potential ecological significance was realized in the early 21st century, following the discovery of giant viruses in aquatic environments in different parts of the world.
This article discusses the fundamental nature of viruses: what they are, how they cause infection, and how they may ultimately cause disease or bring about the death of their host cells. For more-detailed treatment of specific viral diseases, see infection. Viruses occupy a special taxonomic position: they are not plants, animals, or prokaryotic bacteria single-cell organisms without defined nuclei , and they are generally placed in their own kingdom.
In fact, viruses should not even be considered organisms, in the strictest sense, because they are not free-living; i. The nucleic acid encodes the genetic information unique for each virus.
The infective, extracellular outside the cell form of a virus is called the virion. It contains at least one unique protein synthesized by specific genes in the nucleic acid of that virus. In virtually all viruses, at least one of these proteins forms a shell called a capsid around the nucleic acid.
Certain viruses also have other proteins internal to the capsid; some of these proteins act as enzymes , often during the synthesis of viral nucleic acids. Other viruslike particles called prions are composed primarily of a protein tightly complexed with a small nucleic acid molecule. Prions are very resistant to inactivation and appear to cause degenerative brain disease in mammals, including humans.