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96-502: The IBP was organized under the leadership of C. H. Waddington beginning in 1962 and officially started in 1964, with the goal of exploring "The Biological Basis of Productivity and Human Welfare". In its early years, Canadian and European ecologists were the main participants; by 1968, the United States also became heavily involved. However, unlike other more successful applications of the big science model of scientific research,

192-446: A 2D gel electrophoresis . The Bradford assay is a molecular biology technique which enables the fast, accurate quantitation of protein molecules utilizing the unique properties of a dye called Coomassie Brilliant Blue G-250. Coomassie Blue undergoes a visible color shift from reddish-brown to bright blue upon binding to protein. In its unstable, cationic state, Coomassie Blue has a background wavelength of 465 nm and gives off

288-739: A plasmid ( expression vector ). The plasmid vector usually has at least 3 distinctive features: an origin of replication, a multiple cloning site (MCS), and a selective marker (usually antibiotic resistance ). Additionally, upstream of the MCS are the promoter regions and the transcription start site, which regulate the expression of cloned gene. This plasmid can be inserted into either bacterial or animal cells. Introducing DNA into bacterial cells can be done by transformation via uptake of naked DNA, conjugation via cell-cell contact or by transduction via viral vector. Introducing DNA into eukaryotic cells, such as animal cells, by physical or chemical means

384-402: A clear crystalline X-ray pattern I was very eager to continue that work ... Trying to understand 'what really happened' when a very admirable scientist [Randall] models himself on Napoleon is not easy ... [but the letter] was very damaging to her and to me". By November 1951, Wilkins had evidence that DNA in cells as well as purified DNA had a helical structure. Alex Stokes had solved

480-451: A density gradient, which separated the DNA molecules based on their density. The results showed that after one generation of replication in the N medium, the DNA formed a band of intermediate density between that of pure N DNA and pure N DNA. This supported the semiconservative DNA replication proposed by Watson and Crick, where each strand of the parental DNA molecule serves as a template for

576-505: A graduate student Raymond Gosling obtained X-ray photographs of DNA that showed that the long, thin DNA molecule in the sample from Signer had a regular, crystal-like structure in these threads. Gosling later said "When... I first saw all those discrete diffraction spots ...emerging on the film in the developing dish was a truly eureka moment....we realised that if DNA was the gene material then we had just shown that genes could crystallize! " This initial X-ray diffraction work at King's College

672-567: A high quality image of the B-form X-ray diffraction pattern, now identified as photograph 51 , that Franklin had produced in March 1952. Wilkins had shown this image produced by Franklin without notifying or receiving authorization from the principal investigator who produced the image. With the knowledge that Pauling was working on DNA and had submitted a model of DNA for publication, Watson and Crick mounted one more concentrated effort to deduce

768-519: A high-quality image of "B" form DNA ( Photo 51 ), which Gosling had made in 1952, after which his supervisor Rosalind Franklin "put it aside" as she was leaving King's College London. Wilkins showed it to Watson. This image, along with the knowledge that Linus Pauling had proposed an incorrect structure of DNA, "mobilised" Watson and Crick to restart model building. With additional information from research reports of Wilkins and Franklin, obtained via Max Perutz , Watson and Crick correctly described

864-526: A host's immune system cannot recognize the bacteria and it kills the host. The other, avirulent, rough strain lacks this polysaccharide capsule and has a dull, rough appearance. Presence or absence of capsule in the strain, is known to be genetically determined. Smooth and rough strains occur in several different type such as S-I, S-II, S-III, etc. and R-I, R-II, R-III, etc. respectively. All this subtypes of S and R bacteria differ with each other in antigen type they produce. The Avery–MacLeod–McCarty experiment

960-456: A labeled complement of a sequence of interest. The results may be visualized through a variety of ways depending on the label used; however, most result in the revelation of bands representing the sizes of the RNA detected in sample. The intensity of these bands is related to the amount of the target RNA in the samples analyzed. The procedure is commonly used to study when and how much gene expression

1056-518: A mixture of proteins. Western blots can be used to determine the size of isolated proteins, as well as to quantify their expression. In western blotting , proteins are first separated by size, in a thin gel sandwiched between two glass plates in a technique known as SDS-PAGE . The proteins in the gel are then transferred to a polyvinylidene fluoride (PVDF), nitrocellulose, nylon, or other support membrane. This membrane can then be probed with solutions of antibodies . Antibodies that specifically bind to

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1152-495: A model with the phosphate backbones at the center. Upon viewing the model of the proposed structure, Franklin told Watson and Crick that it was wrong. Franklin based this on two observations. First, experiments by J.M. Gulland showed that the CO- and NH 2 groups of the bases could not be titrated , and so were probably inaccessible. Secondly, crystallographic evidence showed that the structural units of DNA were progressively separated by

1248-436: A reddish-brown color. When Coomassie Blue binds to protein in an acidic solution, the background wavelength shifts to 595 nm and the dye gives off a bright blue color. Proteins in the assay bind Coomassie blue in about 2 minutes, and the protein-dye complex is stable for about an hour, although it is recommended that absorbance readings are taken within 5 to 20 minutes of reaction initiation. The concentration of protein in

1344-408: A single slide. Each spot has a DNA fragment molecule that is complementary to a single DNA sequence . A variation of this technique allows the gene expression of an organism at a particular stage in development to be qualified ( expression profiling ). In this technique the RNA in a tissue is isolated and converted to labeled complementary DNA (cDNA). This cDNA is then hybridized to the fragments on

1440-472: A three-year research fellowship that would fund Rosalind Franklin in his laboratory. Franklin was delayed in finishing her work in Paris. Late in 1950, Randall wrote to Franklin to inform her that rather than work on protein, she should take advantage of Wilkins's preliminary work and that she should do X-ray studies of DNA fibers made from Signer's samples of DNA. Early in 1951 Franklin finally arrived. Wilkins

1536-462: A viewpoint on the interdisciplinary relationships between molecular biology and other related fields. While researchers practice techniques specific to molecular biology, it is common to combine these with methods from genetics and biochemistry . Much of molecular biology is quantitative, and recently a significant amount of work has been done using computer science techniques such as bioinformatics and computational biology . Molecular genetics ,

1632-601: A year earlier. Some of those working on DNA in the United Kingdom feared that Pauling would quickly solve the DNA structure once he recognized his error and put the backbones of the nucleotide chains on the outside of a model of DNA. After March 1952 Franklin concentrated on the X-ray data for the A-form of less hydrated DNA while Wilkins tried to work on the hydrated B-form. Wilkins was handicapped because Franklin had all of

1728-657: Is a) on the base: b) on the helices: The Centre for Molecular Biodiscovery at the University of Auckland , launched in 2002, was renamed the Maurice Wilkins Centre in 2006. Wilkins was married twice. His first wife, Ruth, was an art student whom he met whilst he was at Berkeley. Their marriage ended in divorce, and Ruth bore her son by Wilkins after their divorce. Wilkins married his second wife Patricia Ann Chidgey in 1959. They had four children, Sarah, George, Emily and William. His widow Patricia and

1824-423: Is a branch of biology that seeks to understand the molecular basis of biological activity in and between cells , including biomolecular synthesis, modification, mechanisms, and interactions. Though cells and other microscopic structures had been observed in living organisms as early as the 18th century, a detailed understanding of the mechanisms and interactions governing their behavior did not emerge until

1920-439: Is also a long tradition of studying biomolecules "from the ground up", or molecularly, in biophysics . Molecular cloning is used to isolate and then transfer a DNA sequence of interest into a plasmid vector. This recombinant DNA technology was first developed in the 1960s. In this technique, a DNA sequence coding for a protein of interest is cloned using polymerase chain reaction (PCR), and/or restriction enzymes , into

2016-439: Is becoming more affordable and used in many different scientific fields. This will drive the development of industries in developing nations and increase accessibility to individual researchers. Likewise, CRISPR-Cas9 gene editing experiments can now be conceived and implemented by individuals for under $ 10,000 in novel organisms, which will drive the development of industrial and medical applications. The following list describes

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2112-413: Is called transfection . Several different transfection techniques are available, such as calcium phosphate transfection, electroporation , microinjection and liposome transfection . The plasmid may be integrated into the genome , resulting in a stable transfection, or may remain independent of the genome and expressed temporarily, called a transient transfection. DNA coding for a protein of interest

2208-410: Is centrifuged and the pellet which contains E.coli cells was checked and the supernatant was discarded. The E.coli cells showed radioactive phosphorus, which indicated that the transformed material was DNA not the protein coat. The transformed DNA gets attached to the DNA of E.coli and radioactivity is only seen onto the bacteriophage's DNA. This mutated DNA can be passed to the next generation and

2304-401: Is find yourself a good protein". Wilkins knew that proper experiments on the threads of purified DNA would require better X-ray equipment. Wilkins ordered a new X-ray tube and a new microcamera. He also suggested to Randall that the soon-to-be-appointed Rosalind Franklin should be reassigned from work on protein solutions to join the DNA effort. By the summer of 1950 Randall had arranged for

2400-433: Is found in a cDNA library . PCR has many variations, like reverse transcription PCR ( RT-PCR ) for amplification of RNA, and, more recently, quantitative PCR which allow for quantitative measurement of DNA or RNA molecules. Gel electrophoresis is a technique which separates molecules by their size using an agarose or polyacrylamide gel. This technique is one of the principal tools of molecular biology. The basic principle

2496-454: Is known as horizontal gene transfer (HGT). This phenomenon is now referred to as genetic transformation. Griffith's experiment addressed the pneumococcus bacteria, which had two different strains, one virulent and smooth and one avirulent and rough. The smooth strain had glistering appearance owing to the presence of a type of specific polysaccharide – a polymer of glucose and glucuronic acid capsule. Due to this polysaccharide layer of bacteria,

2592-472: Is now inside a cell, and the protein can now be expressed. A variety of systems, such as inducible promoters and specific cell-signaling factors, are available to help express the protein of interest at high levels. Large quantities of a protein can then be extracted from the bacterial or eukaryotic cell. The protein can be tested for enzymatic activity under a variety of situations, the protein may be crystallized so its tertiary structure can be studied, or, in

2688-456: Is occurring by measuring how much of that RNA is present in different samples, assuming that no post-transcriptional regulation occurs and that the levels of mRNA reflect proportional levels of the corresponding protein being produced. It is one of the most basic tools for determining at what time, and under what conditions, certain genes are expressed in living tissues. A western blot is a technique by which specific proteins can be detected from

2784-484: Is susceptible to influence by strong alkaline buffering agents, such as sodium dodecyl sulfate (SDS). The terms northern , western and eastern blotting are derived from what initially was a molecular biology joke that played on the term Southern blotting , after the technique described by Edwin Southern for the hybridisation of blotted DNA. Patricia Thomas, developer of the RNA blot which then became known as

2880-400: Is that DNA fragments can be separated by applying an electric current across the gel - because the DNA backbone contains negatively charged phosphate groups, the DNA will migrate through the agarose gel towards the positive end of the current. Proteins can also be separated on the basis of size using an SDS-PAGE gel, or on the basis of size and their electric charge by using what is known as

2976-412: Is then exposed to a labeled DNA probe that has a complement base sequence to the sequence on the DNA of interest. Southern blotting is less commonly used in laboratory science due to the capacity of other techniques, such as PCR , to detect specific DNA sequences from DNA samples. These blots are still used for some applications, however, such as measuring transgene copy number in transgenic mice or in

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3072-520: Is used to detect post-translational modification of proteins. Proteins blotted on to the PVDF or nitrocellulose membrane are probed for modifications using specific substrates. A DNA microarray is a collection of spots attached to a solid support such as a microscope slide where each spot contains one or more single-stranded DNA oligonucleotide fragments. Arrays make it possible to put down large quantities of very small (100 micrometre diameter) spots on

3168-612: The News Chronicle of London, on Friday 15 May 1953, entitled "Why You Are You. Nearer Secret of Life." The news reached readers of The New York Times the next day; Victor K. McElheny, in researching his biography of Watson, Watson and DNA: Making a Scientific Revolution , found a clipping of a six-paragraph New York Times article written from London and dated 16 May 1953 with the headline "Form of 'Life Unit' in Cell Is Scanned." The article ran in an early edition and

3264-656: The Proceedings of the Royal Society on phosphorescence and electron traps. Wilkins received a PhD for this work in 1940. During World War II Wilkins developed improved radar screens at Birmingham, then worked on isotope separation at the Manhattan Project at the University of California, Berkeley during the years 1944–45. Meanwhile, Randall had been appointed to the Chair of Physics at

3360-565: The Medical Research Council Unit, Cavendish Laboratory , were the first to describe the double helix model for the chemical structure of deoxyribonucleic acid (DNA), which is often considered a landmark event for the nascent field because it provided a physico-chemical basis by which to understand the previously nebulous idea of nucleic acids as the primary substance of biological inheritance. They proposed this structure based on previous research done by Franklin, which

3456-543: The Natural Sciences Tripos , specialising in Physics, and received a Bachelor of Arts degree in 1938. Mark Oliphant , who was one of Wilkins' instructors at St. John's, had been appointed to the Chair of Physics at the University of Birmingham , and had appointed John Randall to his staff. Wilkins became a PhD student of Randall at the University of Birmingham . In 1945, they published four papers in

3552-583: The University of St Andrews . In 1945, he appointed Wilkins as Assistant Lecturer in his department at the University of St Andrews. Randall was negotiating with the Medical Research Council (MRC) to set up a laboratory to apply the experimental methods of physics to problems of biology. The combination of these disciplines as biophysics was a novel idea. The MRC told Randall that this had to be done in another university. In 1946 Randall

3648-425: The genetic code is a triplet code, where each triplet (called a codon ) specifies a particular amino acid. Furthermore, it was shown that the codons do not overlap with each other in the DNA sequence encoding a protein, and that each sequence is read from a fixed starting point. During 1962–1964, through the use of conditional lethal mutants of a bacterial virus, fundamental advances were made in our understanding of

3744-422: The northern blot , actually did not use the term. Named after its inventor, biologist Edwin Southern , the Southern blot is a method for probing for the presence of a specific DNA sequence within a DNA sample. DNA samples before or after restriction enzyme (restriction endonuclease) digestion are separated by gel electrophoresis and then transferred to a membrane by blotting via capillary action . The membrane

3840-528: The 1980s to track down acid rain as a major cause of forest decline . In tropical areas, the LAMTO project held by French professor Maxime Lamotte  [ fr ] in Ivory Coast provided a thorough analysis of the savannah energy budget and a profound knowledge of almost all biodiversity present in this savannah. Molecular biology Molecular biology / m ə ˈ l ɛ k j ʊ l ər /

3936-801: The 20th century, when technologies used in physics and chemistry had advanced sufficiently to permit their application in the biological sciences. The term 'molecular biology' was first used in 1945 by the English physicist William Astbury , who described it as an approach focused on discerning the underpinnings of biological phenomena—i.e. uncovering the physical and chemical structures and properties of biological molecules, as well as their interactions with other molecules and how these interactions explain observations of so-called classical biology, which instead studies biological processes at larger scales and higher levels of organization. In 1953, Francis Crick , James Watson , Rosalind Franklin , and their colleagues at

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4032-640: The Bradford assay can then be measured using a visible light spectrophotometer , and therefore does not require extensive equipment. This method was developed in 1975 by Marion M. Bradford , and has enabled significantly faster, more accurate protein quantitation compared to previous methods: the Lowry procedure and the biuret assay. Unlike the previous methods, the Bradford assay is not susceptible to interference by several non-protein molecules, including ethanol, sodium chloride, and magnesium chloride. However, it

4128-461: The DNA model was Phoebus Levene , who proposed the "polynucleotide model" of DNA in 1919 as a result of his biochemical experiments on yeast. In 1950, Erwin Chargaff expanded on the work of Levene and elucidated a few critical properties of nucleic acids: first, the sequence of nucleic acids varies across species. Second, the total concentration of purines (adenine and guanine) is always equal to

4224-456: The IBP lacked a clear, socially and scientifically pressing goal. Many biologists, particularly molecular biologists and evolutionary ecologists , were sharply critical of the IBP, which they viewed as throwing money at ill-defined or relatively unimportant problems and reducing the freedom of scientists to choose their own research projects. The main results of the IBP were five biome studies,

4320-480: The Swiss scientist Rudolf Signer . The DNA from Signer's lab was much more intact than the DNA which had previously been isolated. Wilkins discovered that it was possible to produce thin threads from this concentrated DNA solution that contained highly ordered arrays of DNA suitable for the production of X-ray diffraction patterns. Using a carefully bundled group of these DNA threads and keeping them hydrated, Wilkins and

4416-553: The War. The Biophysics Unit, several more experimental physics groups and the theoretical group started to move in, during the early months of 1952. The laboratories were opened formally by Lord Cherwell on 27 June. Wilkins' article for Nature described both departments, consistent with his leadership role and prestige within the college at large. At King's College, Wilkins pursued, among other things, X-ray diffraction work on ram sperm and DNA that had been obtained from calf thymus by

4512-461: The addition of water, leading to the formation of a gel and then a solution. Franklin believed that the simplest explanation of this was for the hydrophilic part of the molecule to be on the outside. Crick tried to get Wilkins to continue with additional molecular modeling efforts, but Wilkins did not take this approach. Early in 1952, Wilkins began a series of experiments on sepia sperm which were very encouraging. "I...got much clearer patterns than

4608-437: The array and visualization of the hybridization can be done. Since multiple arrays can be made with exactly the same position of fragments, they are particularly useful for comparing the gene expression of two different tissues, such as a healthy and cancerous tissue. Also, one can measure what genes are expressed and how that expression changes with time or with other factors. There are many different ways to fabricate microarrays;

4704-473: The atomic level. Molecular biologists today have access to increasingly affordable sequencing data at increasingly higher depths, facilitating the development of novel genetic manipulation methods in new non-model organisms. Likewise, synthetic molecular biologists will drive the industrial production of small and macro molecules through the introduction of exogenous metabolic pathways in various prokaryotic and eukaryotic cell lines. Horizontally, sequencing data

4800-403: The bacteriophage's protein coat with radioactive sulphur and DNA with radioactive phosphorus, into two different test tubes respectively. After mixing bacteriophage and E.coli into the test tube, the incubation period starts in which phage transforms the genetic material in the E.coli cells. Then the mixture is blended or agitated, which separates the phage from E.coli cells. The whole mixture

4896-451: The basic mathematics of helical diffraction theory and thought that Wilkins's X-ray diffraction data indicated a helical structure in DNA. Wilkins met with Watson and Crick and told them about his results. This information from Wilkins, along with additional information gained by Watson when he heard Franklin talk about her research during a King's College research meeting, stimulated Watson and Crick to create their first molecular model of DNA,

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4992-780: The children from their marriage survived him. In the years before World War II, he was an anti-war activist, joining the Cambridge Scientists' Anti-War Group . He joined the Communist Party , until the invasion of Poland by the Soviet Army in September 1939. Formerly classified UK security service papers reveal that Wilkins came under suspicion of leaking atomic secrets. The files, released in August 2010, indicate surveillance of Wilkins ended by 1953. "After

5088-736: The conclusion of the program in June 1974. Far more influential than any of the IBP biome studies was contemporary Hubbard Brook ecosystem study of 1963–1968, which—lacking the hierarchical organization of IBP projects—grew gradually according to individual scientists' interest and involved more informal collaboration. One of the most influential IBP projects in Europe was the Solling Project in Lower Saxony (Germany), led by Heinz Ellenberg . Evidence from here proved decisive in

5184-493: The development of new technologies and their optimization. Molecular biology has been elucidated by the work of many scientists, and thus the history of the field depends on an understanding of these scientists and their experiments. The field of genetics arose from attempts to understand the set of rules underlying reproduction and heredity , and the nature of the hypothetical units of heredity known as genes . Gregor Mendel pioneered this work in 1866, when he first described

5280-481: The double-helix structure of DNA in 1953. Wilkins continued to test, verify, and make significant corrections to the Watson–Crick DNA model and to study the structure of RNA. Wilkins, Crick, and Watson were awarded the 1962 Nobel Prize for Physiology or Medicine , "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". Wilkins

5376-401: The engineering of gene knockout embryonic stem cell lines . The northern blot is used to study the presence of specific RNA molecules as relative comparison among a set of different samples of RNA. It is essentially a combination of denaturing RNA gel electrophoresis , and a blot . In this process RNA is separated based on size and is then transferred to a membrane that is then probed with

5472-479: The expectation that DNA X-ray diffraction work was her project. Wilkins returned to the laboratory expecting, on the other hand, that Franklin would be his collaborator and that they would work together on the DNA project that he had started. The confusion over Franklin's and Wilkins' roles in relation to the DNA effort (which later developed into considerable tension between them) is clearly attributable to Randall. In his letter of appointment he told Franklin "as far as

5568-412: The experiment involved growing E. coli bacteria in a medium containing heavy isotope of nitrogen ( N) for several generations. This caused all the newly synthesized bacterial DNA to be incorporated with the heavy isotope. After allowing the bacteria to replicate in a medium containing normal nitrogen ( N), samples were taken at various time points. These samples were then subjected to centrifugation in

5664-507: The experimental X-ray effort [on DNA] is concerned, there will be at the moment only yourself and Gosling". However, Randall never informed Wilkins of his decision to give Franklin sole responsibility for the DNA effort and Wilkins only learned of the letter years after Franklin's death. He later wrote "My opinion is very clear: that Randall was very wrong to have written to Rosalind telling her that Stokes and I wished to stop our work on DNA, without consulting us. After Raymond [Gosling] and I got

5760-399: The extract. They discovered that when they digested the DNA in the extract with DNase , transformation of harmless bacteria into virulent ones was lost. This provided strong evidence that DNA was the genetic material, challenging the prevailing belief that proteins were responsible. It laid the basis for the subsequent discovery of its structure by Watson and Crick. Confirmation that DNA is

5856-504: The functions and interactions of the proteins employed in the machinery of DNA replication , DNA repair , DNA recombination , and in the assembly of molecular structures. In 1928, Frederick Griffith , encountered a virulence property in pneumococcus bacteria, which was killing lab rats. According to Mendel, prevalent at that time, gene transfer could occur only from parent to daughter cells. Griffith advanced another theory, stating that gene transfer occurring in member of same generation

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5952-526: The genetic material which is cause of infection came from the Hershey–Chase experiment . They used E.coli and bacteriophage for the experiment. This experiment is also known as blender experiment, as kitchen blender was used as a major piece of apparatus. Alfred Hershey and Martha Chase demonstrated that the DNA injected by a phage particle into a bacterium contains all information required to synthesize progeny phage particles. They used radioactivity to tag

6048-461: The good DNA. Wilkins got new DNA samples, but it was not as good as the original sample he had obtained in 1950 and which Franklin continued to use. Most of his new results were for biological samples like sperm cells, which also suggested a helical structure for DNA. In July 1952 Franklin reported to him and Stokes that her newest results made her doubt the helical nature of the A-form. In early 1953 Watson visited King's College and Wilkins showed him

6144-522: The implications of this unique structure for possible mechanisms of DNA replication. Watson and Crick were awarded the Nobel Prize in Physiology or Medicine in 1962, along with Wilkins, for proposing a model of the structure of DNA. In 1961, it was demonstrated that when a gene encodes a protein , three sequential bases of a gene's DNA specify each successive amino acid of the protein. Thus

6240-523: The initial 1953 series of publications on the double helix structure of DNA, Wilkins continued research as leader of a team that performed a range of meticulous experiments to establish the helical model as valid among different biological species, as well as in living systems, to establish the universality of the double helix structure. He became deputy director of the MRC Biophysics Unit at King's in 1955, and succeeded Randall as director of

6336-579: The largest of which were the Grassland Biome project and the Eastern Deciduous Forest Biome project (both of which had ties to Oak Ridge National Laboratory , which provided tracer isotopes for nutrient- and energy-flow experiments). Though the impact of these studies was modest, the IBP marked a dramatic increase in the scale of funding for ecosystem ecology, which remained high (relative to earlier levels) even after

6432-434: The laws of inheritance he observed in his studies of mating crosses in pea plants. One such law of genetic inheritance is the law of segregation , which states that diploid individuals with two alleles for a particular gene will pass one of these alleles to their offspring. Because of his critical work, the study of genetic inheritance is commonly referred to as Mendelian genetics . A major milestone in molecular biology

6528-415: The most common are silicon chips, microscope slides with spots of ~100 micrometre diameter, custom arrays, and arrays with larger spots on porous membranes (macroarrays). There can be anywhere from 100 spots to more than 10,000 on a given array. Arrays can also be made with molecules other than DNA. Allele-specific oligonucleotide (ASO) is a technique that allows detection of single base mutations without

6624-399: The need for PCR or gel electrophoresis. Short (20–25 nucleotides in length), labeled probes are exposed to the non-fragmented target DNA, hybridization occurs with high specificity due to the short length of the probes and even a single base change will hinder hybridization. The target DNA is then washed and the unhybridized probes are removed. The target DNA is then analyzed for the presence of

6720-463: The pharmaceutical industry, the activity of new drugs against the protein can be studied. Polymerase chain reaction (PCR) is an extremely versatile technique for copying DNA. In brief, PCR allows a specific DNA sequence to be copied or modified in predetermined ways. The reaction is extremely powerful and under perfect conditions could amplify one DNA molecule to become 1.07 billion molecules in less than two hours. PCR has many applications, including

6816-700: The previous year.....when I met [Sir William Lawrence] Bragg by chance I showed him the pattern [which] very clearly offered strong evidence for a helical structure for DNA....the sharp sperm patterns were very inspiring, and had the special interest that sperm were real live objects and not just purified DNA extracted by chemists from living material". Wilkins was particularly interested in whether living samples would yield meaningful X-ray diffraction patterns – his results showed they could. During 1952, Franklin also refused to participate in molecular modeling efforts and continued to work on step-by-step detailed analysis of her X-ray diffraction data ( Patterson synthesis). By

6912-405: The probe via radioactivity or fluorescence. In this experiment, as in most molecular biology techniques, a control must be used to ensure successful experimentation. In molecular biology, procedures and technologies are continually being developed and older technologies abandoned. For example, before the advent of DNA gel electrophoresis ( agarose or polyacrylamide ), the size of DNA molecules

7008-530: The protein of interest can then be visualized by a variety of techniques, including colored products, chemiluminescence , or autoradiography . Often, the antibodies are labeled with enzymes. When a chemiluminescent substrate is exposed to the enzyme it allows detection. Using western blotting techniques allows not only detection but also quantitative analysis. Analogous methods to western blotting can be used to directly stain specific proteins in live cells or tissue sections. The eastern blotting technique

7104-479: The scientist with most diverse experience of physics and Assistant Director of the unit, had general oversight of the varied projects besides direct involvement in his personal research projects that included new types of optical microscopy. King's College received funding to build completely new Physics and Engineering Departments where vaults beneath the Strand level College forecourt had been destroyed by bombs during

7200-531: The spring of 1952, Franklin had received permission from Randall to ask to transfer her fellowship so that she could leave King's College and work in John Bernal 's laboratory at Birkbeck College , also in London. Franklin remained at King's College until the middle of March 1953. Linus Pauling had published a proposed but incorrect structure of DNA, making the same basic error that Watson and Crick had made

7296-607: The structure of DNA. From 1969 to 1991, Wilkins was the founding President of the British Society for Social Responsibility in Science . In 2000, King's College London opened the Franklin-Wilkins Building in honour of Dr. Franklin's and Professor Wilkins' work at the college. The wording on the DNA sculpture (donated by James Watson) outside Clare College 's Thirkill Court, Cambridge, England

7392-504: The structure of DNA. Through Max Perutz , his thesis supervisor, Crick gained access to a progress report from King's College that included useful information from Franklin about the features of DNA she had deduced from her X-ray diffraction data. Watson and Crick published their proposed DNA double helical structure in a paper in the journal Nature in April 1953. In this paper Watson and Crick acknowledged that they had been "stimulated by....

7488-421: The study of gene expression, the detection of pathogenic microorganisms, the detection of genetic mutations, and the introduction of mutations to DNA. The PCR technique can be used to introduce restriction enzyme sites to ends of DNA molecules, or to mutate particular bases of DNA, the latter is a method referred to as site-directed mutagenesis . PCR can also be used to determine whether a particular DNA fragment

7584-532: The study of gene structure and function, has been among the most prominent sub-fields of molecular biology since the early 2000s. Other branches of biology are informed by molecular biology, by either directly studying the interactions of molecules in their own right such as in cell biology and developmental biology , or indirectly, where molecular techniques are used to infer historical attributes of populations or species , as in fields in evolutionary biology such as population genetics and phylogenetics . There

7680-554: The synthesis of a new complementary strand, resulting in two daughter DNA molecules, each consisting of one parental and one newly synthesized strand. The Meselson-Stahl experiment provided compelling evidence for the semiconservative replication of DNA, which is fundamental to the understanding of genetics and molecular biology. In the early 2020s, molecular biology entered a golden age defined by both vertical and horizontal technical development. Vertically, novel technologies are allowing for real-time monitoring of biological processes at

7776-486: The theory of Transduction came into existence. Transduction is a process in which the bacterial DNA carry the fragment of bacteriophages and pass it on the next generation. This is also a type of horizontal gene transfer. The Meselson-Stahl experiment was a landmark experiment in molecular biology that provided evidence for the semiconservative replication of DNA. Conducted in 1958 by Matthew Meselson and Franklin Stahl ,

7872-451: The total concentration of pyrimidines (cysteine and thymine). This is now known as Chargaff's rule. In 1953, James Watson and Francis Crick published the double helical structure of DNA, based on the X-ray crystallography work done by Rosalind Franklin which was conveyed to them by Maurice Wilkins and Max Perutz . Watson and Crick described the structure of DNA and conjectured about

7968-616: The unit from 1970 to 1972. Wilkins was elected a Fellow of the Royal Society (FRS) in 1959 and an EMBO Member in 1964. In 1960 he was presented with the American Public Health Association 's Albert Lasker Award , and in 1962 he was made a Commander of the Order of the British Empire. Also in 1962 he shared the Nobel Prize in Physiology or Medicine with Watson and Crick for the discovery of

8064-701: The unpublished results and ideas" of Wilkins and Franklin. The first Watson-Crick paper appeared in Nature on 25 April 1953. The members of the Cambridge and King's College laboratories agreed to report their interlocking work in three papers with continuous pagination in Nature . Sir Lawrence Bragg, the director of the Cavendish Laboratory , where Watson and Crick worked, gave a talk at Guy's Hospital Medical School in London on Thursday 14 May 1953 which resulted in an article by Ritchie Calder in

8160-443: The use of molecular biology or molecular cell biology in medicine is now referred to as molecular medicine . Molecular biology sits at the intersection of biochemistry and genetics ; as these scientific disciplines emerged and evolved in the 20th century, it became clear that they both sought to determine the molecular mechanisms which underlie vital cellular functions. Advances in molecular biology have been closely related to

8256-415: Was a New Zealand -born British biophysicist and Nobel laureate whose research spanned multiple areas of physics and biophysics, contributing to the scientific understanding of phosphorescence , isotope separation , optical microscopy , and X-ray diffraction . He is known for his work at King's College London on the structure of DNA . Wilkins' work on DNA falls into two distinct phases. The first

8352-474: Was a landmark study conducted in 1944 that demonstrated that DNA, not protein as previously thought, carries genetic information in bacteria. Oswald Avery , Colin Munro MacLeod , and Maclyn McCarty used an extract from a strain of pneumococcus that could cause pneumonia in mice. They showed that genetic transformation in the bacteria could be accomplished by injecting them with purified DNA from

8448-470: Was appointed Wheatstone Professor of Physics, in charge of the entire Physics department at King's College, London, with the funding to set up a Biophysics Unit. He brought Wilkins with him as Assistant Director of the unit. They appointed a team of scientists trained in both the physical and biological sciences. The "management philosophy" was to explore the use of many techniques in parallel, to find which looked promising, and then to focus on these. Wilkins, as

8544-455: Was away on holiday and missed an initial meeting at which Raymond Gosling stood in for him along with Alex Stokes , who, like Crick, would solve the basic mathematics that make possible a general theory of how helical structures diffract X-rays. No work had been done on DNA in the laboratory for several months; the new X-ray tube sat unused, waiting for Franklin. Franklin ended up with the DNA from Signer, Gosling became her PhD student, and she had

8640-675: Was born in Pongaroa , New Zealand, where his father, Edgar Henry Wilkins, was a medical doctor. His older sister was the translator and poet Eithne Wilkins . His family had come from Dublin, where his paternal and maternal grandfathers were, respectively, Headmaster of Dublin High School and a Chief of Police. The Wilkinses moved to Birmingham , England when Maurice was 6. Later, he attended Wylde Green College and then went to King Edward's School, Birmingham from 1929 to 1934. Wilkins went to St John's College, Cambridge in 1935; he studied

8736-495: Was conveyed to them by Maurice Wilkins and Max Perutz . Their work led to the discovery of DNA in other microorganisms, plants, and animals. The field of molecular biology includes techniques which enable scientists to learn about molecular processes. These techniques are used to efficiently target new drugs, diagnose disease, and better understand cell physiology. Some clinical research and medical therapies arising from molecular biology are covered under gene therapy , whereas

8832-650: Was done in May or June 1950. It was one of the X-ray diffraction photographs taken in 1950, shown at a meeting in Naples a year later, that sparked James Watson's interest in DNA causing him to write "suddenly I was excited about chemistry.....I began to wonder whether it would be possible for me to join Wilkins in working on DNA". At that time Wilkins also introduced Francis Crick to the importance of DNA. Crick advised him to work on proteins telling Wilkins "what you ought to do

8928-543: Was in 1948–1950, when his initial studies produced the first clear X-ray images of DNA, which he presented at a conference in Naples in 1951 attended by James Watson . During the second phase, 1951–52, Wilkins produced clear "B form" X-shaped images from squid sperm, images he sent to James Watson and Francis Crick , causing Watson to write "Wilkins... has obtained extremely excellent X-ray diffraction photographs" [of DNA]. In 1953, Wilkins' group coordinator Sir John Randall instructed Raymond Gosling to hand over to Wilkins

9024-414: Was the discovery of the structure of DNA . This work began in 1869 by Friedrich Miescher , a Swiss biochemist who first proposed a structure called nuclein , which we now know to be (deoxyribonucleic acid), or DNA. He discovered this unique substance by studying the components of pus-filled bandages, and noting the unique properties of the "phosphorus-containing substances". Another notable contributor to

9120-464: Was then pulled to make space for news deemed more important. (The New York Times subsequently ran a longer article on 12 June 1953). The Cambridge University undergraduate newspaper Varsity also ran its own short article on the discovery on Saturday 30 May 1953. Bragg's original announcement at a Solvay conference on proteins in Belgium on 8 April 1953 went unreported by the press. Following

9216-512: Was typically determined by rate sedimentation in sucrose gradients , a slow and labor-intensive technique requiring expensive instrumentation; prior to sucrose gradients, viscometry was used. Aside from their historical interest, it is often worth knowing about older technology, as it is occasionally useful to solve another new problem for which the newer technique is inappropriate. Maurice Wilkins Maurice Hugh Frederick Wilkins CBE FRS (15 December 1916 – 5 October 2004)

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