It is in the possession of the University of Turbingen, Germany. Credit: Alfons Renz. DNA is central to biotechnology and medicine by virtue of the fact that it not only provides the basic blueprint for all life, it is a fundamental determinant of how the body functions and the disease process. It is also critical to the identification of pathogens. Aside from its medical uses, the fact that DNA is unique to each individual makes it a vital forensic tool identifying criminals, the remains of a missing person, and determining the biological parent of a child.
Within agriculture DNA is also used to help improve animal livestock and plants. The discovery of DNA stretches back to , when Friedrich Miescher, a Swiss physician and biologist, began examining leucocytes, a type of white blood cell, he had sourced from pus collected on fresh surgical bandages. This he did while working in the laboratory of Felix Hoppe-Seyler in Tubingen, Germany as part of project to determine the chemical building blocks of cells.
On looking through the microscope he observed that a substance separated from the solution of the cells whenever he added an acid and then dissolved again once alkali was added. The compound bore no resemblance to any known protein. Believing the substance to originate from the nuceli of the cell, Miescher nicknamed it 'nuclein'. On investigating further he discovered nuclein to be present in many other tissues. While possessing only simple tools and methods, by Miescher had come close to working out the genetic role of nuclein.
He lacked sufficient communication skills, however, to convey the importance of what he had found to the wider scientific world. In Albrecht Kossel, a German biochemist, renamed Miescher's compound deoxyribonucleic acid DNA based on the fact that he had discovered it to be a nucleic acid. Following this, he began working out its chemical composition. By he determined it to be made up of five nitrogen bases: adenine A , cytosine C , guanine G , thymine T and uracil U.
For many decades DNA remained little studied because it was assumed to be an inert substance incapable of carrying genetic material because of its simple structure. Proteins were instead thought to be the carriers of genetic material. In part this was because they had a more complex structure, being made up of 20 different amino acids.
It would not be until the mid 20th century that attitudes towards DNA began to change. From the early s, Avery began to investigate how a type of non-infectious bacteria associated with pneumonia could transform into dangerous virulent forms if mixed with dead cells from the virulent strain and carried this trait into their offspring.
The phenomenon had been first observed by Fred Griffith, a British physician, in While not universally accepted at the time, Avery's finding helped kindle a new interest in DNA. By the s a number of researchers had begun to investigate the structure of DNA in the hope that this would reveal how the molecule worked.
Their work determined DNA to be a long linear molecule made up of two strands coiled around each other in a spiral configuration later known as the 'double helix'. Each strand was made up of four complementary nucleotides, chemical subunits: adenine A , cytosine C , guanine G and thymine T. The two strands were oriented in opposite directions so that adenine always joined thymines A T and cytosines were linked with guanines C G.
Watson and Crick argued this structure helped each strand to reconstruct the other and facilitate the passing on of hereditary information. The analysis of DNA is pivotal to understanding both the biological mechanisms of life and diseases that arise when this process goes wrong. Many different applications have been developed to understand this process. Today scientists can analyse the molecule through a range of techniques, including DNA sequencing which helps work out its structure, through to PCR, which rapidly amplifies tiny quantities of DNA into billions of copies.
Such techniques underpin all tests carried out today to for example identify a genetic mutation that causes cancer, or to determine whether a person carries a gene for a hereditary disease that can be passed on to their offspring. In addition, scientists have found ways to manipulate and construct new forms of DNA, known as recombinant DNA or gene cloning.
Such technology is crucial to the mass production of many drugs, such as interferon, and the development of gene therapy. A nucelotide called tuberculinic acid found to bind to the protein tuberculin. It is now regarded as the precursor to the discovery of DNA methylation. Johnson and R. Coghill reported detecting a minor amount of methylated cytosine derivative as byproduct of hyrdrolysis of tuberculinic acid with sulfuric acid but other scientists struggled to replicate their results.
Barbara McClintock and Harriet Creighton, her graduate student, provided first experimental proof that genes are positioned on chromosomes. Erwin Schrodinger proposed that life was passed on from generation to generation in a molecular code.
Victor Ingram breaks the genetic code behind sickle-cell anaemia using Sanger's sequencing technique. Francis Crick presented the theory that the main function of genetic material is to control the synthesis of proteins. First comprehensive protein sequence and structure computer data published as 'Atlas of Protein Sequence and Structure'.
Chromosome with a specific gene isolated from hybrid cells produced from fused mouse and human cells. Process called repair replication for synthesising short DNA duplexes and single-stranded DNA by polymerases is published. Janet Mertz forced to halt experiment to clone recombinant DNA in bacteria after safety concerns raised. Temporary moratorium called for on genetic engineering until measures taken to deal with potential biohazards.
DNA methylation proposed as important mechanism for the control of gene expression in higher organisms. Proto-oncogenes suggested to be part of the genetic machinery of normal cells and play important function in the developing cell. Nobel Prize given in recognition of discovery of restriction enzymes and their application to the problems of molecular genetics.
University of Edinburgh scientists published the successful isolation and cloning DNA fragments of the hepatitis B virus in Escherichia coli. Biogen applied for European patent to clone fragment of DNA displaying hepatitis B antigen specificity. First chimeric monoclonal antibodies developed, laying foundation for safer and more effective monoclonal antibody therapeutics. Carol Greider and Elizabeth Blackburn announced the discovery of telomerase, an enzyme that adds extra DNA bases to the ends of chromosomes.
Results released from first small-scale clinical trial of recombinant interferon-alpha therapy for post-transfusion chronic hepatitis B. BRCA1, a single gene on chromosome 17, shown to be responsible for many breast and ovarian cancers.
Method devised to isolate methylated cytosine residues in individual DNA strands providing avenue to undertake DNA methylation genomic sequencing. FDA approved the use of genetically engineered interferon-alpha, Intron A, for the treatment of hepatitis B. First experimental evidence showing links between diet and DNA methylation and its relationship with cancer. First evidence published to demonstrate reduced DNA methylation contributes to formation of tumours.
Publication of complete genome sequence of the first multicellular organism, the nematode worm Caenorhabditis elegans. Complete sequences of the genomes of the fruit fly Drosophila and the first plant, Arabidopsis, are published. Oxford Nanopore Technology decides to focus its resources on developing nanopore sequencing for DNA sequencing. DNA sequencing proves useful to documenting the rapid evolution of Streptococcus pneumococci in response to the application of vaccines.
DNA sequencing utilised for identifying neurological disease conditions different from those given in the original diagnosis. Respond to or comment on this page on our feeds on Facebook , Instagram or Twitter. Facebook Twitter Donate to WiB. DNA Definition DNA is a complex, long-chained molecule that contains the genetic blueprint for building and maintaining all living organisms.
Importance DNA is central to biotechnology and medicine by virtue of the fact that it not only provides the basic blueprint for all life, it is a fundamental determinant of how the body functions and the disease process. Discovery The discovery of DNA stretches back to , when Friedrich Miescher, a Swiss physician and biologist, began examining leucocytes, a type of white blood cell, he had sourced from pus collected on fresh surgical bandages.
Application The analysis of DNA is pivotal to understanding both the biological mechanisms of life and diseases that arise when this process goes wrong. He did not know they played role in heredity.
This he did in The significance of his work, first published in , was initially missed by the scientific community. Miescher later suggested that nucleic acids could carry the genetic blueprint for life. In addition to his work on nucleic acids, Miescher demonstrated carbon dioxide concentrations in blood regulate breathing. He worked out how chromosomes divide during cell meiosis. Based on studies of an intestinal worm found in horses, he also showed that fertilisation involves the union of two half-nuclei, one form the male sperm cell and one from the female egg, each containing half the the number of chromosomes found in all cells.
He later demonstrated that the chromosome number is constant for every body cell in each species. Originally calling this substance nuclein, Miescher's discovery paved the way for the identification of what we today call nucleic acids and the understanding of DNA as the carrier of inheritance.
He also idenfitied the components of DNA: adenine, guanine, thymine, cytosine, deoxyribose and a phosphate group and showed that these components were linked together by nucleotides, phosphate-sugar base units. Born to Jewish parents, Levene emigrated to the US in as a result of anti-semitic progroms.
He was appointed the head of the biochemical laboratory at the Rockefeller Institute of Medical Research in where he spent the rest of his career.
In he and colleagues conducted a series of experiments in mice using two sets of bacteria, one smooth virulent and the other rough nonvirulent , associated with pneumonia. In the first instance they injected the virulent bacteria into the mouse, which went on to die. Next they injected the non-virulent bacteria into a mouse, which survived. They then heated the virulent bacteria to kill it and injected it into a mouse, which survived.
Following this they injected a mixture of heat-killed bacteria with the virulent bacteria into the mouse, which died. Finally they injected a mixture of harmless bacteria with DNA extracted from the heated lethal bacteria in a mouse which died.
The experiment showed that the harmless bacteria became lethal when mixed with DNA from the virulent bacteria. It was discovered by Walther Flemming with the help of analine dyes. He also described the behaviour of chromosomes during cell division. Flemming first published a comprehensive outline of is findings in his book Zellsubstanz, Kern und Zelltheilung Cell substance, nucleus and cell division in Miescher, was the first person to isolate nucleic acids from the nuclei of white blood cells.
In addition to his work on nucleic acids, Miescher demonstrated that carbon dioxide concentrations in blood regulate breathing. It is now regarded as the precursor to the discovery of DNA methylation Ruppel Philipps University of Marburg Pauling was a chemist and biochemist who helped to pioneer quantum chemistry and mechanics.
He combined methods from x-ray crystallography, molecular model building and quantum chemistry. Pauling was the first to find the alpha helix structure of proteins. In he won the Nobel Prize in Chemistry for his 'research on the nature of the chemical bond and its application to the elucidation of the structure of complex structures. Pauling also won the Nobel Peace Prize in , which was awarded to him for his opposition to nuclear weapons.
The terms are published in his paper Om arvelighed i samfund og i rene linie. This lays the foundation for the study of genetics. He was one of the first scientists to show the pivotal role of high energy phosphates, like adenosine triphosphate, in the storage and release of energy.
During this work he discovered the enzyme polynucleotide phosphorylase, which plays an important role in the synthesis of ribonucleic acid RNA.
This enzyme provided the foundation for the subsequent synthesis of artificial RNA and the breaking of the human genetic code. He also synthesised two important biochemical compounds: adenosine triphosphate ATP and flavin adenine dinucleotide FAD. The book becomes the founding text of genetics. Together with Mahlon Hoagland and Mary Stephenson he showed that protein synthesis was activated by adenosine 5'-triphosphate and that ribosomes were the site of protein assembly.
He also subsequently helped to discover transfer RNA and is credited with laying the foundation for the development of antisense therapies, a type of gene therapy. He is credited with improving the nucleic acid hybridisation technique.
It is now used for analysing the organisation of the genome, studying gene expression and for developing recombinant DNA. He also developed the central dogma of molecular biology which explained how genetic information flowed within a biological system, moving from DNA to RNA and then protein.
His subsequent work looked at the way in which the brain works and the nature of consciousness. He obtained the first x-ray patterns on DNA in This work led to his winning the Nobel Prize in Following his work on DNA, Wilkins directed his attention to studying the structure of various forms of RNA and a wide group of genetic problems, like ageing.
In his younger years, Wilkins was recruited to work on the Manhattan atomic bomb project during the war. Wilkins became profoundly disillusioned with nuclear weapons after the bombing of Japan and was the president of the British Society for Social Responsibility in Science from to In he and his team isolated the first enzyme known to be involved in the replication of DNA.
It would be called DNA polymerase I. For this work Kornberg shared the Nobel Prize for Medicine. The Prize was given for the discovery of the 'mechanisms in the biological synthesis of ribonucleic acid and deoxyribonucleic acid. He was also pivotal to the development of the dideoxy chain-termination method for sequencing DNA molecules, known as the Sanger method.
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.
She is best known for having taken photo 51, in , which provided the first evidence of the double helix structure of DNA. She took the photo using x-ray crystallography. Sadly Franklin died too early to receive the Nobel Prize for her work. She helped elucidate the first co-ordinated stress response.
This she did by studying the response of bacteria to UV radiation. Witkins was one of the first few women to be elected to the US National Academy of Sciences, in She was also awarded the National Medal of Science in This was based on some experiments he pursued with mutant T4 bacteriophages, known as r mutants. In he spotted abnormal behaviour in one mutant strain and a year later devised a technique to measure the recombination frequency between different r mutant strains to map the substructure of a single gene.
His work laid the path to determining the detailed structure of viral genes. Benzer also coined the term cistron to denote functional subunits of genes. Together with Ronald Konopka, his student, Benzer also discovered the first gene to control an organism's sense of time, in He helped demonstrate that the chemical composition and function of a new cell is determined by four nucleotides in DNA and that the nucleotide code is transmitted in groups of three, called codons, and these codons instruct the cell to start and stop the production of proteins.
His work also laid the foundation for the development of polymerase chain reaction PCR , a technique that makes it possible to make billions of copies of small fragments of DNA. One of the few to realise the importance of nucleic acids before Watson and Crick uncovered the structure of DNA in , Smith helped to elucidate the structure of ribonucleic acid molecules RNA , the genetic material of many plant and animal viruses.
This was helped by his development of paper chromatographic methods for analysing nucleosides and other units which make up DNA. He also helped to discover rare and unexpected modifications of DNA bases in bacterial genomes which are now understood to prevent attack from DNA viruses.
This was based on some experiments he performed with Edward Tatum in which involved mixing two different strains of bacteria. Their experiments also demonstrated for the first time that bacteria reproduced sexually, rather than by cells splitting in two, thereby proving that bacterial genetic systems were similar to those of multicelluar organisms.
Later on, in , working with Norton Zinder, Lederberg found that certain bacteriophages viruses that affect bacteria could carry a bacterial gene from one bacterium to another. In Lederberg shared the Nobel Prize for Medicine for 'discoveries concerning genetic recombination and the organisation of the genetic material of bacteria. Johnson, R. This he did as part of his work to study viral chromosomes. He was awarded the Nobel Prize in for this work.
His technique paved the way to the development of genetic engineering and the modern biotechnology industry. Berg was also instrumental in the setting up of the Asilomar Conference on Recombinant DNA, in , which drew up the first guidelines for experiments with genetic engineering. The Prize was given on the back of some experiments Nirenberg conducted in and which identified particular codons 3 chemical units of DNA that specified each of the 20 amino acids that make up protein molecules.
On the basis of this he hypothesises that some transforming principle from the heat-killed strain is responsible for making the harmless strain virulent.
Watson also helped set up the Human Genome Project, which he headed up between to He left the project after campaigning against the NIH patenting the human genome. In he became the second person to publish his fully sequenced genome online.
This he did to encourage the development of personalised medicine. He was also instrumental in the application of genetic engineering to agricultural plants to improve their output and resistance to pests, salt and drought. His work inspired the use of restriction enzymes for many different biotechnology applications, including DNA sequencing and the construction of recombinant DNA.
He was awarded the Nobel Prize in Physiology or Medicine in for his work on restriction enzymes. 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. Together with Matthew Medelsohn, Stahl showed that the double-stranded helix molecule of DNA separates into two strands and that each of these strands serve as a template for the production of a new strand of DNA.
They did this in Following this work, Stahl did extensive work on bacteriophages, viruses that infect bacteria, and their genetic recombination.
In he established that DNA in T4 bacteriophages is circular rather than linear. Eight years later he and his wife, Mary, found a DNA sequence in the lambda bacteriophage necessary to initiate genetic recombination. This laid the foundation 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.
In he found a way to make Escherichia coli acquire a plasmid that made it resistant to the antibiotic tetracycline. He also discovered with Herbert Boyer a restriction enzyme that could cleave a circular plasmid at a single site. This laid the foundation for their joint experiment in which demonstrated the feasibility of combining and replicating genetic information from different species.
Their experiment involved inserted a gene for frog ribosomal RNA into bacterial cells which then expressed the gene. The nucleotides combine with each other by covalent bonds known as phosphodiester bonds or linkages. Other scientists like Linus Pauling and Maurice Wilkins were also actively exploring this field.
Pauling had discovered the secondary structure of proteins using X-ray crystallography. Unfortunately, by then Franklin had died, and Nobel prizes are not awarded posthumously. Figure 2. Scientist Rosalind Franklin discovered b the X-ray diffraction pattern of DNA, which helped to elucidate its double helix structure.
Watson and Crick proposed that DNA is made up of two strands that are twisted around each other to form a right-handed helix. Base pairing takes place between a purine and pyrimidine; namely, A pairs with T and G pairs with C. Adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs.
The base pairs are stabilized by hydrogen bonds; adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds.
The sugar and phosphate of the nucleotides form the backbone of the structure, whereas the nitrogenous bases are stacked inside.
Each base pair is separated from the other base pair by a distance of 0. Therefore, ten base pairs are present per turn of the helix. The diameter of the DNA double helix is 2 nm, and it is uniform throughout.
Only the pairing between a purine and pyrimidine can explain the uniform diameter. The twisting of the two strands around each other results in the formation of uniformly spaced major and minor grooves Figure 3. Figure 3. DNA has a a double helix structure and b phosphodiester bonds. The genetic information of an organism is stored in DNA molecules. How can one kind of molecule contain all the instructions for making complicated living beings like ourselves?
What component or feature of DNA can contain this information? It has to come from the nitrogen bases, because, as you already know, the backbone of all DNA molecules is the same. The sequence of these four bases can provide all the instructions needed to build any living organism. But think about the English language, which can represent a huge amount of information using just 26 letters.
Even more profound is the binary code used to write computer programs. This code contains only ones and zeros, and think of all the things your computer can do. The DNA alphabet can encode very complex instructions using just four letters, though the messages end up being really long.
A gene from any cell of any living thing can be copied, transferred and understood by any other living thing to make the same protein. For example, human insulin is now made by microbes genetically engineered with the human DNA recipe for human insulin. That is, a copy of the human insulin gene is transferred to microbes, and those microbes read the human insulin gene recipe and make insulin, even though the microbes — having no blood or blood sugar — have no use for insulin.
Similarly, most hard cheeses now are made with chymosin a milk clotting enzyme generated by genetically modified microbes. From a scientific perspective, we can confidently state that life began at least once, about 3.
Answer: unlikely. The evidence is based on DNA being the sole common feature of all living things. More importantly, the language DNA uses to convey information is common to all; the same language is read and understood by all living things.
And most importantly, the DNA language is not just the common language used by all species; it is the only language used by any species. When considering the number of potential languages DNA might have used instead, the fact that all known life forms use the same language of DNA to communicate the same information is compelling evidence that life arose only once.
The fact that all living things use DNA as their physical hardware, and share a single language of DNA as their intellectual software, is evidence that all living things derive from a common ancestor way back when. Other evidence includes gene homology a similar DNA base sequence of similar genes in diverse species and a common synteny the linear order of adjacent genes in the DNA of a chromosome.
The consensus in the scientific community is that life started once and that evolution provided our current diversity of living things.
To be sure, scientists argue strenuously over the mechanics of evolution, and timing, and duration, and other minutia concerning evolutionary processes. Curious humans have always been interested in heredity, pondering how children acquired the features of their parents. More recently, molecular geneticists have learned not only how to read the information carried by a DNA strand, but also how to edit or supplement it.
These innovations allow development of a number of commercial products such as the aforementioned insulin and cheese. The sequence of these four bases can provide all the instructions needed to build any living organism. But think about the English language, which can represent a huge amount of information using just 26 letters. Even more profound is the binary code used to write computer programs. This code contains only ones and zeros, and think of all the things your computer can do. The DNA alphabet can encode very complex instructions using just four letters, though the messages end up being really long.
For example, the E. The human genome all the DNA of an organism consists of around three billion nucleotides divided up between 23 paired DNA molecules, or chromosomes. The information stored in the order of bases is organized into genes : each gene contains information for making a functional product. The genetic information is first copied to another nucleic acid polymer , RNA ribonucleic acid , preserving the order of the nucleotide bases.
In order for DNA to function effectively at storing information, two key processes are required. First, information stored in the DNA molecule must be copied, with minimal errors, every time a cell divides. This ensures that both daughter cells inherit the complete set of genetic information from the parent cell.
Second, the information stored in the DNA molecule must be translated , or expressed. In order for the stored information to be useful, cells must be able to access the instructions for making specific proteins, so the correct proteins are made in the right place at the right time.
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