How did the work of other scientists help Crick and Watson to develop their theory for the structure of DNA?
By Ash Modha, SF-HCJames Watson and Francis Crick are the two scientists credited with discovering the structure of DNA They published their theory on the double helical structure in 1952 and in 1962, along with Maurice Wilkins, received the Nobel Prize in Physiology or Medicine (The Nobel Prize Organisation).
However, while it is a common misconception, they did not discover DNA itself. It was Swiss chemist Friedrich Miescher who discovered nucleic acids back in 1869; nearly 100 years before Crick, Watson and Wilkins received their Nobel Prize Originally called ‘nuclein’, Miescher’s discovery came about while researching the chemical composition of leukocytes. He noticed an unknown precipitate which was neither a lipid, nor a protein and, on further analysis, was shown to contain large amounts of phosphorus. Meischer’s further experiments and hypotheses for the roles of ‘nuclein’ were remarkably accurate; he noted how the amount increased preceding cell division, hinting at DNA’s role in this process, and even theorised that ‘nuclein’ may have a role in transmitting genetic traits, although he later rejected this possibility (Dahm 565-81)
Another scientist who laid the groundwork for Crick and Watson was Phoebus Levene Levene furthered our understanding of nucleic acids massively, experimenting on the nucleic acid of yeast. He worked out the three components of a nucleotide (a pentose sugar, a nitrogenous base and a phosphate group), discovered both ribose and deoxyribose and correctly determined the fashion in which RNA and DNA molecules are put together (Pray) In 1919 he published his paper on the structure of yeast nucleic acid and concluded that nucleic acids were polymers composed of nucleotides with one of 4 nitrogenous bases (Levene 415–424). While some aspects of his theories were wrong, most were correct,
making his work integral to later research on nucleic acids
While more and more was being discovered about DNA, its purpose was still unproven, until, in 1944, Oswald Avery published his paper that showed how genes, and therefore genetic traits, were passed on through and encoded in deoxyribonucleic acid (Cobb R55–R60)
Avery’s paper was perhaps ahead of his time - while today we know his theory to be correct, Avery did not win a Nobel Prize or any major award that would have solidified his status as one of the most integral scientists in our modern understanding of genetics (Ghose 135–144).
Following behind, and inspired by Avery, was Erwin Chargaff. Chargaff set out to work out if there were differences between DNA in different organisms Using a new method of paper chromatography, he noticed that
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the order of nucleotides varied between different species and that, even though the nucleotide order was different, in all organisms DNA had shared properties - namely that there were the same 4 nitrogenous bases present with nucleotides always having the same structure and components The other, and perhaps most important, discovery of Chargaff's base pairing Whilst it wasn’t until Watson and Crick that this was fully understood, Chargaff’s analysis revealed that the amounts of adenine and thymine in DNA were roughly equal, and the amounts of cytosine and guanine were also roughly equal We know now that this is due to hydrogen bonds occurring between complementary base pairings of A&T and C&G (Pray)
Finally, we come to Watson and Crick and how much they did (or didn’t do) The work of the aforementioned scientists laid the groundwork for Watson and Crick to create their theory for the structure of DNA. Levene showed that DNA was a polynucleotide, each nucleotide with one of 4 possible nitrogenous bases, a pentose sugar and a phosphate group. Avery proved the importance of DNA, its role in genetics and thus, the reason why, as Meischer originally noted, the amount of DNA in a cell doubles before cell division Chargaff’s work into base pairing also eliminated certain possible structures for DNA and this gave Watson and Crick some of the rules that their model had to follow
While it is true that Crick and Watson did publish the correct theory for the structure of DNA, their final work was massively impacted by the work of another scientist who did not receive proper credit. Rosalind Franklin was a scientist working in the biophysical department of King’s College London, investigating DNA and imaging it using X-Ray crystallography While she was not the only person working on DNA imagine, she was unique in that she focused on DNA fibres instead of crystals. During her work she discovered two forms of DNA molecule, type A and B, with the latter occurring at high humidity Type B DNA’s structure was slightly different; this meant it was more easily imaged and that later, it would be imaging of this DNA that changed science forever (Klug 808–810)
Eventually Franklin took ‘Photo 51’, a photograph of a fibre of type B DNA that indicated the 3D structure of DNA and became one of the most important photographs in scientific history
Yet Franklin’s name is not commonly associated with the discovery of the structure of DNA This is in part due to the betrayal of one of her junior colleagues working under her at King’s College London. In 1953, Maurice Wilkins, without Franklin’s permission, showed photograph 51 to James Watson and Francis Crick Credit
where credit is due, they had theorised a helical structure to DNA but Franklin's work was the final piece in the puzzle The cross shaped structure the image showed brought Watson and Crick closer and closer to proving their theory for the structure of DNA. Unfortunately, the photograph was not enough information and, once again without Franklin’s permission, they obtained the data from her full reports on her experiments with X-Ray crystallography on type B DNA Franklin’s numbers allowed Watson and Crick to complete the calculations they needed to prove the double helix structure of DNA. (Danylova and Komisarenko 154–165)
Rosalin Franklin died of ovarian cancer in 1958 while those who had, in effect, stolen her work went on to win a Nobel Prize. Franklin lived long enough for her findings to change history, but not long enough to be awarded a Nobel Prize for it - even though Wilkins, who was jointly awarded said prize and worked under her instructions, was recognised for his work That is not to discredit anyone involved in the discovery of the structure of DNA’s hard work; Watson, Crick, Wilkins and many others did experiments of their own and advanced science in their own right, but that Rosalind Franklin, a rare female scientist in a male dominated field, was unfairly left out of the history books
Bibliography
Cobb, Matthew “Oswald Avery, DNA, and the Transformation of Biology.” Current Biology, vol. 24, no. 2, Jan 2014, pp R55–R60
Dahm, Ralf “Discovering DNA: Friedrich Miescher and the early years of nucleic acid research.” Human genetics vol 122,6 (2008): 565-81 doi:10.1007/s00439-007-0433-0
Danylova, T V, and Komisarenko, S V “Standing on the Shoulders of Giants: James Watson, Francis Crick, Maurice Wilkins, Rosalind Franklin and the Birth of Molecular Biology” The Ukrainian Biochemical Journal, vol 92, no 4, 10 Sept 2020, pp 154–165
Ghose, Tarunendu. “Oswald Avery: The Professor, DNA, and the Nobel Prize That Eluded Him ” Canadian Bulletin of Medical History, vol 21, no 1, Apr 2004, pp 135–144, doi: 10.3138/cbmh.21.1.135.
KLUG, A Rosalind Franklin and the Discovery of the Structure of DNA. Nature 219, 808–810 (1968).
Levene, P A The structure of yeast nucleic acid IV Ammonia hydrolysis Journal of Biological Chemistry 40, 415–424 (1919)
Pray, L (2008) Discovery of DNA structure and function: Watson and Crick Nature Education 1(1):100
The Nobel Prize in Physiology or Medicine 1962. NobelPrize org Nobel Prize Outreach AB 2022 Thu 13 Oct 2022nobelprize org/prizes/medicine/1962
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The Fourier Series: the lens to see the mysteries of the world
By Daria Gal, 11GHave you ever thought about how many circles make a cat?
This Hocus-Pocus can be easily accomplished with the magic of the Fourier transform (FT), which went through a long period of evolution, starting from the Fourier Formula The beauty of the Fourier formula is in its simplicity: where
les corps solides [1] (Treatise on the propagation of heat in solid bodies)
Interestingly, in the same year the Brothers Grimm published a collection of stories, amongst which one can find the well-known tale of Snow White We note that image and sound processing, which later is developed based on the Fourier Series, is used by the evil stepmother to talk to her magic mirror and spy on her stepdaughter Since the 19th Century the Fourier Series has been used in applied mathematics to investigate Brownian motion [2] and later the Thermal Diffusivity in polymers [3], although its general applicability to efficiently solving scientific problems was limited until the arrival of modern electronic computation
Fourier’s formula is founded on the idea of representing the irregular distribution of temperature with the frequencies of many component sinusoidal waves In this way, Joseph Fourier solved the Heat Equation, which brought him a prize from the Academy in 1812 for his essay Mémoire sur la propagation de la chaleur dans
Before we can begin our exciting expedition into understanding and applying Fourier’s mathematical representation of the phenomena around us, we shall consider the events and advances, which preceded Fourier’s discovery In the beginning of the 18th century Brook Taylor proved that vibrating strings could be represented by a simple sinusoid [4], to which Daniel Bernoulli added that instead of one simple function, one could superpose two or more simple functions to represent a more complex function, for which solutions can be found [5] Thus, the very foundations of Analysis were built
When investigating the propagation of heat, Fourier elaborated on existing ideas and investigated how to
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calculate the coefficients (Eq 1) for the decomposition of a complex function, which had previously been overlooked The heat equation considers the propagation of heat from one material to another, with different temperatures. For simplicity, we shall consider the temperatures 1 and -1 Fourier used the superposition of sine and cosine waves as a solution of (Eq 2)
This was a significant event in the world of mathematics, as the original distribution of temperatures was a discontinuous step function We can note that the more terms taken, the more accurate the representation of this function (Fig 2, Fig 3) This is the reason why in the general formula (Eq 1) we have the sum to infinity Based on the boundary conditions, a system of equations is formed By solving the system of equations, we obtain the values of the coefficients
by Augustine Louis Cauchy in 1822 [6] According to the Euler Formula [7], an exponential can be used to express cosines and sines
Therefore, the can be used to represent a vector in �� ������ the complex plane, as the radius of a circle (Fig.1). The more such vectors, and thus circles, used the more accurate the depiction of the initial function (Fig 2, Fig 3) The advantage of FT over the Fourier Series is that FT can represent an arbitrary function (Fig 2) However, a large spectrum of problems still remained inaccessible with FT, due to computational complexity To the rescue came the “Fast Fourier Transform” (FFT) [8] algorithm in 1965, developed by professors James Cooley and John Tukey at IBM’s Watson Research centre, which exponentially reduces the computational time This was another crucial event for the practical application of the Fourier transform
Signal Processing
It is difficult to imagine modern life without signal processing, which would not be possible without Edward Charles Titchmarsh’s Theorem 85, presented in his work in 1937 [9], which is greatly relied upon in problems of image processing For us to understand signal processing in a nutshell, we shall consider the two dimensional Fourier Transform, let this be . Here, the grey scale image in Fig 4 is represented by function , which assigns the value of intensity (Fig 4) to each
Whilst the Fourier Series allows to represent a periodic function, it has been further generalised in the form of Fourier Transform (FT)
coordinate Function is real valued ��= (����,����) ��(����,����) and defined in the range [0, 1] The transformed function assigns a value to each special frequency pair, ��(ω��,ω��)
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In order to manipulate the frequency
domain, we shall introduce the function , such ��(ω��,ω��) that one can increase or decrease certain frequencies. The inverse Fourier, of the product gives the �� 1 [�� · ��] desired distribution of new values of intensity The schematic representation of the process can be seen in Fig.5.
Applications
Nowadays the Fourier Transform plays a vital role in audio and image processing and compression The Fourier Transform was initially used in audio processing, in order to improve the signal-noise ratio Society developed to transmit a great deal of information through photos and film. For example, the Fourier transform was used on 19 November 1949 at Cheltenham, Maryland [10] in a recording of cosmic waves to remove the background noise of the photograph and increase the contrast (Fig 6a) Also, the images received from electron (Fig.6b) and atomic microscopes, which are widely used to examine structures, are enhanced, using the Fourier transform In recent decades the Fourier transform has become increasingly useful to process large amounts of biomedical data that are the result of advancements of the emerging biomedical sensing and imaging technologies, including magnetic resonance imaging (MRI), x-ray computed tomography (CT) imaging [11] (Fig 6c), and ultrasound imaging
even rigour” and for being “nothing short of impossible”
Little did they know that future society would be dependent on Fourier’s formula, with applications that were well ahead of Fourier’s time
Bibliography:
1. Mémoire sur la théorie analytique de la chaleur, Written 1807, Distributed in 1812, Joseph Fourier
2 Series Expansion Approximations of Brownian Motion for Non-Linear Kalman Filtering of Diffusion Processes, IEEE Transactions on Signal Processing, vol. 62, no. 6, pp. 1514-1524, March 2014, Lyons, Simon M J , Sarkka, Simo, Storkey, Amos J
3. Thermal diffusivity and mechanical properties of polymer matrix composites, Journal of Applied Physics 112, 093513, 2012, Bernd Weidenfeller, Mathias Anhalt, and Stefan Kirchberg
4 Methodus Incrementorum Directa et Inversa, 1715 , Brook Taylor
5. Wave propagation in Periodic Structures: Electric Filters and Crystal Lattice, 1946, Brillouin L
6. A. L. Cauchy, “Théorie de la propagation des ondes a la surface d’un fluide pesant d’une profondeur indéfinie, Note XIX, Sur les fonctions réciproques,” Mémoires présentés par divers savants á l’Académie Royale des Sciences de l’Institut de France et imprimés par son ordre Sciences mathématiques et physiques. Tome I. Imprimé par autorisation du Roi a l’Imprimerie royale; 1827 Œuvres Complètes d’Augustin Cauchy, Series 1, Tome 1, 1882.
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Introductio in analysin infinitorum, 1748, Leonhard Euler
The Fast Fourier transform and its applications, Prentice Hall, 1988, Oran Brigham
Fourier’s work, written more than 200 years ago, was initially heavily criticised by Poisson, Biot and Lagrange for lacking “something [ ] on the score of generality and
9.
Introduction to the theory of Fourier integrals (2nd ed ), Oxford University, 1937, E Titchmarsh 10
Adaptive frequency domain filtering of legacy cosmic ray recordings, 2008, Gunther Drevin
11 Deformable CT Registration Using Fourier Basis Functions in 3D, 2010, A R Osorio, Roberto A Isoardi, German Mato, Conference on Graphics, Patterns and Images (SIBGRAPI), 2010 23rd SIBGRAPI
γ= (ω��,ω��)
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The Demon That Almost Broke Physics
By Adeline Goh, 9GImagine if one demon broke all laws we currently believe to govern our universe It sounds preposterous, but a thought experiment proposed by James Clerk Maxwell did just this; scientists were left baffled for 115 years over a seemingly simple problem The problem is called Maxwell’s demon
The experiment goes something like this: there is a room full of gas split into two chambers, separated by a trapdoor A demon sits in the chamber with the gas It lets the fastest moving particles through the door, whereas the slower particles stay in the first chamber The second chamber, as a result of this, will have a higher average energy than the first, equating to a higher temperature. This breaks the second law of thermodynamics, but how and why does one demon cause such unrest?
energies so they can break their intermolecular bonds, but solids cannot and are therefore very ordered This randomness is entropy.
The second law of thermodynamics states that the amount of entropy, or energy, in an isolated system, will only increase over time By an isolated system, we mean one in which neither energy nor mass can pass (hence it cannot lose energy to its surroundings) This is the case because the isolated systems will lead towards thermal equilibrium, a state where the energy is more or less uniform throughout the structure, meaning that the entropy cannot decrease A thermal flask is an example of an isolated system; when the lid is closed, the energy will not transfer to its surroundings (more or less), therefore maintaining its entropy When the lid is open, it is not an isolated system as the energy can now get out and transfer to its surroundings
^ The chambers before the demon has separated the particles against the chambers once the particles have been separated.
For us to understand how the law is broken, we must first understand what the second law of thermodynamics is and how it works In thermodynamics, one of the key concepts is the idea of entropy, a measure of the system’s energy and therefore temperature (a system being any collection of objects) This measure of energy is equally a measure of randomness, as the more energy the particles have, the more disordered they will be Put simply, the higher the energy of the particles, the higher the randomness in which they move. Taking the example of states of matter, a gas is randomly arranged whereas a solid is in a very ordered structure, otherwise it wouldn’t have all the properties a solid has Gases have higher
So how does Maxwell’s demon violate this law? Maxwell designed the thought experiment so that entropy would decrease within the system; as he decreased the randomness of the system, he essentially decreased entropy This should be impossible, if the 2nd law were true
But fear not! Following developments in information theory, the Erasure principle was discovered and it was established that there would need to be information stored and recorded in order to establish when to open and close the door; periodically, this information would need to be erased. The erasure principle states that there would be some sort of rise in entropy from this erasure, and this would compensate for the decrease in entropy
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The principle, discovered by a man called Landauer, works by this equation:
E = kB T ln (2)
Which came from Boltzmann’s earlier entropy formula:
S = kB ln (W)
In the second equation, the S is the entropy, kB is the Boltzmann constant, ln is the natural logarithm and W is the number of possible states of the system The Boltzmann constant is the relation between relative kinetic energy of particles in a gas and the temperature, which, expressed numerically, comes to about 1.38 x 10-23 . ln is the natural logarithm: the logarithm (a base, or a number multiplied to a power) of the base to e (the mathematical constant). The number of states in the system is W (and the base of the aforementioned natural logarithm), in this case being 2: fast moving and slow moving.
Hence, we can see how this equation is taken into the first equation: it is ln (2) instead of W, fitting Boltzmann’s equation but instead also calculating the corresponding energy increase (E) and factoring in T, being the temperature of the heat sink: the flow of energy through the gas This means that the operation of erasing a single bit increases the amount of entropy, thereby increasing the amount of energy
Maxwell’s demon demonstrates the fragility of our laws: how one relatively simple thought experiment can destroy the fundamentals which we believe our universe to be built on This demon came dangerously close to doing so! Although the experiment did turn out to be
impossible, it was by no means a waste of time and instead helped to further our understanding of quantum information theory and erasure While we are no longer haunted by this particular demon, no doubt there will be more to come that will either cement or change our understanding of the universe as we know it
Bibliography: [1]
quantamagazine org/how-maxwells-demon-continues-tostartle-scientists-20210422/
[2] chem libretexts org/Bookshelves/Physical and Theoretic al Chemistry Textbook Maps/Supplemental Modules ( Physical and Theoretical Chemistry)/Thermodynamics/ The Four Laws of Thermodynamics/Second Law of T hermodynamics#:~:text=The%20Second%20Law%20of% 20Thermodynamics,universe%20can%20never%20be%2 0negative
[3] britannica.com/science/entropy-physics
[4] en wikipedia org/wiki/Landauer%27s principle
[5] journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.040 602
[6] en.wikipedia.org/wiki/Laws of thermodynamics
[7] physics aps org/articles/v8/127
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How influential was Rosalind Franklin’s "Photo 51"?
By Emily Ames, SF-CMCDeoxyribose nucleic acid (DNA) is said to have been discovered by James Watson and Francis Crick in the 1950s, however many argue with this statement as it is shown that several other scientists contributed far more greatly to the discovery, therefore deserve more recognition Undoubtedly, the discovery was not just down to a single scientist’s work, and that a plethora of work was done with DNA, and that Watson and Crick were responsible for congregating the work of many, and ultimately presenting the double helix structure.
In 1951, 23-year-old James Watson, a Chicago-born American, arrived at the Cavendish Laboratory in Cambridge¹, where he was presented with a talk on the molecular structure of DNA, which fascinated him greatly. Furthermore, Crick, who was a physicist working in the biological field, was writing a dissertation on the X-ray crystallography of haemoglobin where he met Watson who shared the same fascination over the structure and properties of DNA Both scientists put together several models of DNA and incorporated an abundance of evidence from other scientists, gathered through their research. After several failed attempts at building the model, such as a three-stranded version, and one in which the same bases were paired, such as thymine and thymine, they achieved their break-through in 1953². This model showed that DNA is a double-stranded, helical molecule which consists of two sugar-phosphate backbones on the outside of the helices, and the strands being held together by hydrogen bonds between pairs of complementary nitrogenous bases on the inside The bases are either adenine, thymine, guanine or cytosine, and pairing always occurs between A & T, and C & G ³ This work was then awarded the Nobel Prize in Physiology or Medicine in 1962, along with Maurice Wilkins who also contributed to their discovery
One of the scientists' work which inspired and helped Crick and Watson the most was the work of Rosalind Franklin. She studied at Newnham Women's College at Cambridge University where she read chemistry and gained her PhD, later accepting a job at King's College London where she studied X-ray crystallography.⁴ This process involved the shining of high energy x-rays onto small crystals of DNA, producing images which could be used to study and investigate the structure Franklin used X-ray crystallography to obtain an image of the double-helix structure of DNA, with her most famous picture being Photo 51, which demonstrated the
double-helix structure of deoxyribonucleic acid: the molecule containing the genetic instructions for the development of all living organisms ⁵ This X-ray diffraction picture of the DNA molecule was shown to Watson, by Maurice Wilkins, who worked closely with Franklin at King's College, and was initially Watson's inspiration regarding the idea that DNA had a helix structure and there were two strands which intertwine Using Franklin's photograph and their own data, Watson and Crick created their famous DNA model primarily thanks to her work Furthermore, Watson and Crick published their findings in a one-page paper, with the title "A Structure for Deoxyribose Nucleic Acid," in the British scientific weekly Nature on April 25, 1953, however did not credit the work of Franklin, thus missing her out of the The Nobel Prize ⁶
A scientist who assisted Franklin on her discovery regarding the structure of DNA was a scientist named Maurice Wilkins Wilkins began studying nucleic acids and proteins through X-ray imaging as well, in which he was very successful in isolating single fibres of DNA He then gathered more data about the nucleic acid structure when Rosalind Franklin joined him, as they worked together on the x-ray crystallography ⁷ Wilkins involvement in the formative x-ray diffraction work on DNA allowed him to show the first crystalline symmetrical patterns of DNA, which helped show the symmetry in which the two strands of DNA had, as they are parallel to each other in the double helix structure This, alongside Franklin’s photo 51, helped Watson and Crick develop their model of the DNA structure. Thus Wilkins was credited and awarded The Nobel Prize for his involvement within the discovery of the deoxyribose nucleic acid structure Wilkins was the one who showed Watson Franklin’s work on x-ray crystallography, therefore can be credited majorly for helping piece together the different theories around the actual structure of the nucleic acid
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Friedrich Miescher, another scientist involved with the discovery of DNA, was the first person to isolate nuclein from the cell nuclei, thus, this allowed him to identify DNA as a distinct molecule ⁸ Miescher originally examined leukocytes (types of white blood cells) and obtained the cells for his experiments from the pus on fresh surgical bandages ⁹ He focused on the various types of proteins that make up the leukocytes, as they were considered to be the most promising way of understanding how cells function, furthermore he discovered that proteins and lipids were the main components of the cytoplasm. However, during these tests, Miescher noticed that a substance precipitated from the solution when acid was added and dissolved again when alkali was added, and he realised he had obtained a precipitate of nuclein,
which is now to be known as DNA and chromatin Watson and Crick were able to study DNA thanks to Miescher’s original identification of the biological molecule in 1869, therefore without Miescher, their research and other scientist’s research around the structure would not have been possible.
Erwin Chargaff, a biochemist in the mid 1900s, worked on the organic nitrogenous bases in DNA Chargaff knew that DNA was made up of four different bases: adenine, cytosine, guanine and thymine In his experiments on these bases, he observed that the ratio of cytosine to guanine was one to one, and the ratio of adenine to thymine was also one to one, meaning that the complementary bases always had the same percentage
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to each other¹⁰ This made him question whether the aperiodic order of bases might provide a "genetic code”, as since the percentage of each nitrogenous base was different in every species’ DNA, it could be related to genetic variation. This work on the percentage of bases, and pairing of them, allowed Watson and Crick to develop their theory around the structure of DNA, as they could see how the percentages of bases affects the coil in the double helix The complementary base-pairing enables the base pairs to be packed in the energetically most favourable arrangement in the interior of the double helix, and in this arrangement, each base pair is of similar width, thus holding the sugar-phosphate backbones an equal distance apart along the DNA molecule ¹¹
It is evident that whilst Watson and Crick made a significant discovery surrounding the structure of DNA and how the molecule is designed and what it contains, it is shown that many other scientists contributed greatly to this discovery, and that they are not the only people responsible for discovering the structure of DNA.
Photo 51 taken by Rosalind Franklin in 1952 https://www.bbc.co.uk/news/health-18041884
Bibliography:
¹https://www.sciencehistory.org/historical-profile/james-w atson-francis-crick-maurice-wilkins-and-rosalind-franklin ²https://profiles nlm nih gov/spotlight/sc/feature/doublehe lix
³https://www mun ca/biology/scarr/Watson-Crick Model h tml
⁴https://www nature com/scitable/topicpage/rosalind-fran klin-a-crucial-contribution-6538012/ ⁵https://www.kcl.ac.uk/the-structure-of-dna-how-dr-rosalin d-franklin-contributed-to-the-story-of-life-2#:~:text=The%2 0discovery%20of%20the%20structure,development%20 of%20all%20living%20organisms. ⁶https://wwwyoutube com/watch?v=BIP0lYrdirI ⁷https://www nature com/scitable/topicpage/maurice-wilki ns-behind-the-scenes-of-dna-6540179/
⁸https://wwwyoutube com/watch?v=UFChDmR65kE ⁹https://www sciencedirect com/science/article/pii/S00121 60604008231 ¹⁰ https://wwwyoutube com/watch?v=2TdSnpcDCVc ¹¹Molecular Biology of the Cell. 4th edition. Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter
Reliability of the sources: ⁵https://www kcl ac uk/the-structure-of-dna-how-dr-rosalin d-franklin-contributed-to-the-story-of-life-2#:~:text=The%2 0 discovery%20of%20the%20 structure,development%20of%20all%20li
This website is an accurate and reliable source, as it is the website of King's college London, the university in which Rosalind Franklin attended. They have her work and discoveries in their archives, therefore present accurate information regarding her findings and have a secure and trusted platform to do this on.
⁸https://wwwyoutube com/watch?v=UFChDmR65kE
This video is a less reliable source as whilst their facts are correct, they have not referenced any information stated in the video and they have not shown where any of their facts have come from Whilst this is the case, the video is still informative and contains reliable information, yet it may not be the most reliable source to use surrounding Friedrich Miescher's research
¹¹Molecular Biology of the Cell. 4th edition.
Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter This source is a reliable source of information as the book has been proofread by many scientists and experts in the field of biology and cellular microbiology, thus all the information and facts inside the book are accurate to the time in which it was published and written However, as the book was written in 2002, the scientific analysis will have been updated and studied since then, so some of the information is outdated
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How is antibiotic resistance caused
By Klea Alushani, SF-RGAntibiotics are a type of medication that affect bacterial pathogens They can either kill the bacteria (bacteriocides), or slow the spread (bacteriostatics) Antibiotics can do this by either damaging cell walls (through preventing bonds forming between murein molecules, in turn weakening the cell wall), or preventing protein synthesis (through binding to ribosomes) [1] Following their discovery, antibiotics were used liberally, despite the long term effects of this being unknown, which is now known to be resistance. Antibiotic resistance is when bacteria are able to withstand the effects of antibiotics. This problem is exacerbated through the overuse of antibiotics and not taking a complete course
Before knowing that the overuse of antibiotics could lead to resistance, they were often prescribed unnecessarily This, however, means that more bacteria were exposed to antibiotics, creating a selection pressure. By survival of the fittest, only the bacteria with the advantageous characteristics (in this case, not being affected by the antibiotic) survive, leading them to multiplying, possibly leading to a new generation of this resistant form of the bacterium [2]
Not completing a full course of antibiotics increases antibiotic resistance as it means that some bacteria may not be killed This means that the remaining bacteria are exposed to the antibiotic; these are likely to have advantageous alleles, which, as above, survive and reproduce, increasing the spread of the resistant bacterium
Bacteria can become resistant through mutations in genes, which occur randomly These genes can be found on the plasmids of bacterial cells. Bacteria can pick up plasmids from one another, meaning some bacteria become multi-resistant [3].
Bacteria that are resistant to antibiotics are known as superbugs. Examples include Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile (CD)
MRSA commonly causes skin infections, but can also lead to more life threatening diseases such as lung infections or sepsis Being in contact with surfaces that have touched infected skin, such as towels or skin-on-skin contact, can lead to someone contracting it [4].
CD can cause diarrhoea, stomach ache, and fever It normally lives in the bowel, but can cause an infection due to the disruption of the balance of bacteria following a course of antibiotics [5].
These bacteria present challenges to healthcare systems As a result, it is necessary for hospitals to control and prevent these infections. The methods that they can employ to do this are: controlling antibiotic use; taking hygiene measures; isolating patients; preventing the infection entering the hospital; monitoring levels of healthcare-acquired infections.
As antibiotic overuse has had a vast impact on antibiotic resistance, controlling their usage is therefore imperative By controlling usage, the damaging effects of using them unnecessarily are reduced Studies have shown that increased exposure increases the risk of MRSA isolation [6]. It has also been shown that the ‘overuse of antibiotics led to [a] outbreak of severe diarrhoea caused by [CD]’, and that this was stopped by reducing the use of the antibiotics [7] The reason behind this, in the case of CD, was that the overuse of antibiotics killed off other competitors that the resistant CD faced, meaning it was consequently able to thrive [7]. The problems caused by MRSA and CD are exacerbated by the overuse of antibiotics, and so measures such as making antibiotics only available on prescriptions and completing a full course are vital in promoting the prevention of infection by these bacteria
Hygienic measures can prevent MRSA through reducing transmission and cross-contamination [8], decreasing the likelihood of another person being infected by the bacterium They can prevent CD by maintaining a person’s health, so they do not need a course of antibiotics (which can trigger a CD infection) Measures can include hand washing, not touching nose and mouth, and sanitising surfaces
Isolating patients is when people affected with an illness are separated from those who are not By preventing their contact with non-infected individuals, they are less likely to pass on pathogens as the individuals are not directly exposed In the case of MRSA, this will reduce the spread of it directly; in the case of CD, this can reduce other types of bacterial infections, so that a course of antibiotics is not needed, so the risk of being infected with CD is decreased.
and how are hospitals preventing these infections? The examples of C difficile and MRSA.
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Preventing an infection from entering a hospital can be difficult. If someone is being treated for an illness in a hospital, then that hospital is at a risk of being contaminated. However, wider prevention in society can lead to fewer incidences in hospitals This can be done by promoting individual hygiene, such as discouraging the sharing of towels, which can prevent transmission of MRSA and other (resistant) bacteria
Monitoring levels of healthcare-acquired infections (HAIs) is critical in preventing infections By doing this, it can be seen if current techniques are adequate, or if they need improvements to stop avoidable infections. HAI surveillance can also aid doctors in prescribing the correct antibiotics [9], to reduce unnecessary usage and therefore hinder antibiotic resistance
It is clear that antibiotic resistance poses a huge threat to treating diseases. MRSA and CD are just two examples of the consequences of inappropriate antibiotic use However, the mechanisms discussed can be used in an attempt to limit the harmful effects of these bacteria
Source Evaluation:
[5] can be said to be a highly reliable source This is due to the fact that it comes from the NHS website This means that the nature of it is to educate and promote awareness of different issues in healthcare, which therefore makes it unlikely to misconstrue any information, and not include facts Moreover, as a national establishment, they also have a legal responsibility to not spread misinformation, meaning it can be said to be a trustworthy source.
[7] can also be said to be a reliable source This is because it is an article written by the University of Leeds The source comes from an educational institution, meaning, as above, it is unlikely to misconstrue any information, as it seeks to educate people on their findings Additionally, they have included the paper in which the article was based off of, which clearly displays their methodology and findings, showing transparency in their research, thereby displaying its reliability
[9] can be argued to be a less reliable source This is because it was published in 1998, which makes it relatively old in comparison to the other sources used However, despite the original publishing date, it may still be regarded as valid as the content is not necessarily outdated When determining the source’s credibility, the content appears to still be relevant, justifying its use despite it being an older source
References:
[1] “Antibiotics and Drug Testing (A Level) the science hive” the science hive, https://www.thesciencehive.co.uk/antibiotics-and-drug-te sting-a-level Accessed 5 November 2022
[2] “What is antibiotic resistance? – YourGenome” YourGenome, 25 January 2016, https://wwwyourgenome org/facts/what-is-antibiotic-resis tance/ Accessed 6 November 2022
[3] “Plasmids and co-selection – Antibiotic resistance –ReAct.” ReAct - Action on Antibiotic Resistance, https://www reactgroup org/toolbox/understand/antibiotic -resistance/plasmids-and-co-selection/. Accessed 6 November 2022
[4] “General Information | MRSA ” CDC, https://www.cdc.gov/mrsa/community/index.html. Accessed 6 November 2022
[5] “Clostridium difficile (C diff) infection ” NHS, https://www nhs uk/conditions/c-difficile/ Accessed 6 November 2022
[6] Tacconelli, Evelina. “Does antibiotic exposure increase the risk of methicillin-resistant Staphylococcus aureus (MRSA) isolation? A systematic review and meta-analysis.” 2007, pp 26-38 National Library of Medicine, https://pubmed.ncbi.nlm.nih.gov/17986491/.
[7] Crook, Derrick. “Overuse of antibiotics the main cause of C diff epidemic ” University of Leeds, 25 January 2017, https://www leeds ac uk/news-1/news/article/3978/overus e-of-antibiotics-the-main-cause-of-c-diff-epidemic Accessed 7 November 2022
[8] “Personal hygiene in health care can prevent spread of health care-associated infections | Infection prevention ” ABENA UK, https://www.abena.co.uk/knowledge-center/personal-hyg iene Accessed 6 November 2022
[9] Huovinen, Pentti “Control of antimicrobial resistance: time for action.” BMJ., vol. 317(7159), 1998, pp. 613–614, https://www ncbi nlm nih gov/pmc/articles/PMC1113829/ Accessed 6 November 2022.
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Year 8 Chemistry poems
By Anna James, Aneira Barrett, Eve Comish and Ajuni Arneja
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Editor’s note
Editing the Franklin has been a great experience as I have both got to contribute and read about the fascinating scientific and mathematical topics everyone has chosen. I am looking forward to editing further issues.
Adeline Goh, 9G
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