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- 130 Biology Research Topics for Students in 12222
A study has shown that miRp is highly expressed in proliferative diabetic retinopathy. However, the exact biological functions and mechanisms of miRp in diabetic retinopathy DR progression are cu Flotillin-2 Flot2 is a lipid raft scaffold protein that is thought to be related to neural differentiation. Flot2 is phosphorylated by Fyn, a Src kinase, and causes raft-dependent endocytosis; however, the e Authors: Kei Hanafusa and Nobuhiro Hayashi.
Novel selective EP 4 receptor agonists would assist to further elucidate receptor sub-type function and Authors: Melissa C. Holt, Chi S. Ho, M. Barrett and Adam J. Whole-proteome distributions of protein isoelectric point pI values in different organisms are bi- or trimodal with some variations. It was suggested that the observed multimodality of the proteome-wide pI d Authors: Atsushi Kurotani, Alexander A. Stefanov, Yutaka Yamada and Tetsuya Sakurai.
HPV16 infection is one of the main risk factors involved in the development of cervical cancer, mainly due to the high oncogenic potential of the viral proteins E6 and E7, which are involved in the different p Association of Epstein-Barr virus EBV encoded latent gene products with host ribosomal proteins RPs has not been fully explored, despite their involvement in the aetiology of several human cancers. To gain Authors: J. Riley, Andrew P. Nolin, Larissa C. Wolf and David E. Content type: Methodology article. Endothelial cells ECs play a key role in tissue homeostasis, in several pathological conditions, and specifically in the control of vascular functions.
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ECs are frequently used as in vitro model systems for c Authors: Olli-Pekka A. Korpela, Juho J. The discovery of thermostable DNA polymerases such as Taq DNA polymerase revolutionized amplification of DNA by polymerase chain reaction methods that rely on thermal cycling for strand separation. These metho Several human cancers, especially cervical cancer are caused by the infection of high risk strains of human papillomaviruses HPV , notably HPV It is implicated that the oncoprotein E6 expressed from HPV, i Authors: Maria A.
Iyer, Russell A. Judge, Marc Lake, Denise C. Metabolites are genetically and environmentally determined.
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Consequently, they can be used to characterize environmental exposures and reveal biochemical mechanisms that link exposure to disease. To explore di Podocyte plays an important role in maintaining the integrity and function of the glomerular filtration barrier. Various studies reported that forkhead transcription factor Fox O1 played a key role in anti-o Content type: Review article. The processes of DNA supercoiling and transcription are interdependent because the movement of a transcription elongation complex simultaneously induces under- and overwinding of the DNA duplex and because the Authors: Charles J.
Cardiac stem cells CSCs exhibit age-dependent characteristics. Cited2 has been implicated in the regulation of heart development; however, there is little known about how Cited2 affects CSC aging. Content type: Publisher Correction. During production of the original article , there was a technical error that resulted in author corrections not being rendered in the PDF version of the article. Authors: Gera A. Pavlova, Alyona V. Razuvaeva, Julia V. Popova, Evgeniya N. Andreyeva, Lyubov A.
Yarinich, Mikhail O. It is involved in the regulation of several ce Erdmann and Raphael Stoll. Wntless Wls is a protein that regulates secretion of Wnt signaling molecules from Wnt-producing cells. Wnt signaling is known to be critical for several developmental and homeostatic processes. However, Wnt To-date, no claim regarding finding a consensus sequon for O -glycosylation has been made. Thus, predicting the likelihood of O -glycosylation with sequence and structural information using classical regression ana Authors: Rajaram Gana and Sona Vasudevan.
A popul Authors: Dorothy M. Johnson and Deborah J. Content type: Database. The manual classification of protein domains is approaching its 20th anniversary. ECOD is our mixed manual-automatic domain classification. Over time, the types of proteins which require manual curation has ch Authors: R. The forkhead transcription factor FOXL2 plays a crucial role in blepharophimosis-ptosis-epicanthus inversus syndrome BPES , sex determination, ovary growth and development, and cell cycle regulation.
Colon cancer affects 1. The only curative treatment is surgical resection, but a significant number of Authors: D. Yonar, A. Hypertrophic cardiomyopathy occurs along with pathological phenomena such as cardiac hypertrophy, myocardial fibrosis and cardiomyocyte activity. However, few of the specific molecular mechanisms underlying th In this expo Authors: Helen C. Ghandhi, Sally A. Amundson, David J. Brenner and Igor Shuryak. MicroRNAs miRNAs are increasingly being identified as modulatory molecules for physiological and pathological processes in muscle.
Here, we investigated whether miRNAs influenced the expression of the stress Authors: Bilal A. Russell and Victoria C. Nuclear lamins are type V intermediate filament proteins that maintain nuclear structure and function. The ancient Greek scholars formulated the idea of spontaneous generation of life in which insects and other small animals were thought to arise spontaneously from mud or decaying organic matter.
This idea persisted throughout the Middle Ages with descriptions of successful demonstrations of spontaneous generation of worms, flies, eels, frogs, and other organisms from mud and decaying materials. For example, mice were believed to arise spontaneously from cheese wrapped in rags and kept in a dark place. Frogs were said to form from decaying vegetation in ponds. The appearance of maggots in rotten meat seemed a particularly clear case of spontaneous generation.
The overthrow of the doctrine of spontaneous generation began in the late s with the experiments of Francesco Redi, an Italian physician. In his most famous experiment he showed that maggots did not appear in rotting meat when the meat was protected from flies.
On meat exposed to the open air, maggots develop from eggs laid by flies. The debate reached a peak in the s and was led by an Englishman, John Needham, and an Italian, Lazzaro Spallanzani. These two men did similar experiments but obtained different results. A solution of organic matter, for example mutton gravy, was boiled in a glass vessel, and the vessel was sealed. Needham sealed his vessels with corks and consistently observed the growth of microorganisms several days after boiling the solution. He concluded that the microorganisms had originated spontaneously out of the organic matter.
Spallanzani boiled the organic solutions longer and sealed them more carefully. In some experiments he sealed vessels containing organic solutions by melting the neck of the glass vessel and then boiled the contents. The pressure in the closed vessels was increased by the heating, and therefore the boiling point of the enclosed organic solution was raised. Spallanzani consistently observed that his organic solutions remained free of microorganisms. He concluded that the microorganisms that appeared in solutions heated and left open came from the air. We must conclude that these experimenters were less careful than Spallanzani and had not achieved sterilisation of their solutions.
Many kinds of bacteria and fungi develop into spores when conditions are unfavorable for growth. In the form of a spore the cell is dehydrated, metabolically inert, and enclosed by a thick, tough cell wall. When placed in an environment that is favorable for growth, spores germinate into a metabolically active form and resume growth and reproduction.
Spores can survive for many years in a dried state. They are not killed by brief treatment with boiling water but can be destroyed by prolonged boiling or by autoclaving. Bacterial and fungal spores are everywhere in our environment and are a common component of airborne dust. They are a major nuisance to those who work with animal and plant cell cultures, since a single contaminating spore germinates and grows rapidly in the nutrient media required for cell culture. A further complication is that autoclaving breaks down some of the components in nutrient media required for growth of animal cells.
To avoid the deleterious effects of heat, sterilisation is now often achieved by passing media through an extremely fine filter that removes any microorganisms or their spores. The argument about spontaneous generation was settled to the satisfaction of most scientists only by the experiments of Louis Pasteur in the s. One of his experiments consisted of sterilising nutrient broth by prolonged boiling in a flask with an S-shaped neck.
The flask was open to the air, but airborne spores were trapped in the S-shaped neck, and the broth remained sterile. When the neck of the flask was subsequently broken off, allowing airborne dust to enter, microorganisms began to grow in the broth. Pasteur also showed that microorganisms presumably in spore form could be collected by passing air through a filter made of cotton. The disproof of spontaneous generation leaves us with an enigma.
If cells can arise only from preexisting cells, where did the first cell on Earth come from? The experiments by Spallanzani and Pasteur showed that cells could not arise spontaneously from organic matter, at least under the conditions of their experiments. Modern experiments on this problem are designed to test the hypothesis that under certain conditions, particularly those that might have existed on Earth before the appearance of life, a simple primitive cell might have formed spontaneously.
Thus, biologists accept that cells do not now arise spontaneously from organic material, but most believe that given the right conditions and sufficient time many millions of years , spontaneous generation of a cell did happen at least once, and all contemporary cells have descended from that first cell. In considering the current thinking and experimentation on the origin of life it is necessary to order real and postulated events onto a time scale beginning with the formation of the Earth.
Until the late s the oldest known fossils had been found in sedimentary rocks about million years old. These represented highly evolved invertebrate animals such as trilobites, whose hard shells readily gave rise to fossils.
Term Paper on Cell Biology | Cell | Biology
The fossil record indicates that small invertebrates and plants were the only multicellular organisms in existence from about to million years ago. This interval of million years is called the Cambrian period. The Cambrian period was followed by a succession of periods that are defined by the fossils of progressively more highly evolved plants and animals, extending to the Quaternary period, in which we now live. The period before the appearance of the first fossilised invertebrates, extending from the origin of the Earth 4.
Six hundred million years is an underestimate of the time of appearance of the first multicellular organisms. Multicellular organisms that were structurally simpler, lacking hard shells, and leaving no apparent fossil record undoubtedly preceded the appearance of such highly evolved forms as hard-shelled invertebrates.
Recently, worm tracks have been discovered in rocks at least million years older than fossils from hard-shelled animals, showing that soft bodied multicellular organisms were present at least million years before the start of the Cambrian period, or million years B. We do not know when the first multicellular animals evolved, but it must have been longer than million years ago. Also, however long ago the first multicellular animal evolved, it must have been preceded by an interval in which all organisms were unicellular prokaryotes and eukaryotes.
Furthermore, this interval was most likely preceded by a period in which only progenotes existed. All of this was largely supposition until the late s, when the electron microscope was used in a successful search for microfossils of unicellular organisms in ancient rocks. Many descriptions of microfossils in rocks formed far back in Precambrian times have been published in scientific journals in the last 20 years.
The oldest microfossils discovered so far are filamentous and spherical structures that strongly resemble bacteria, including blue- green bacteria. These microfossils occur abundantly in flint like rocks called chert in South Africa and in rocks of Western Australia, both of which are 3. Cherts formed in Precambrian times also typically contain 0. On the basis of these studies it is now generally believed that life existed on Earth at least 3. It is generally believed that the first cells were highly heterotrophic in their nutrition, obtaining energy and nutrients from an abundance of organic molecules in the environment.
Evolution of photosynthetic prokaryotic organisms followed sometime later. Thus, we may conclude that the first cells, which were probably prokaryotic-like, arose sometime before 3. The fossil record provides an estimate of when eukaryotes originated. This chert is million years old, and unicellular eukaryotes therefore seem to have been well established by that time. Fossils of possibly nucleated cells have also been discovered in Beck Spring dolomite in California, which is about 1. The oldest microfossils that might be remnants of eukaryotic cells have been found in rocks 1. These microfossils are similar in form to existing kinds of unicellular green algae.
Shale from Montana about 1. From these and similar discoveries it is generally believed that eukaryotes originated at least 1.
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Thus, the origin of pre-prokaryotes progenotes preceded the origin of eukaryotes by about 2. Many differences separate contemporary prokaryotes and eukaryotes. They both probably evolved from progenotes, and it is virtually certain that not all the differences arose simultaneously.
130 Biology Research Topics for Students in 12222
Modern prokaryotes probably do not differ in structure nearly as much from the progenote ancestor as do modern eukaryotes. The origin of eukaryotes must have occurred with a single change, and this was followed by subsequent evolution of a succession of changes that now make eukaryotes very different from prokaryotes. We have little idea of which difference represents the first step in divergence of eukaryotes from the progenote.
It might have been the acquisition of any one of a number of properties-new kinds of genes, multiple chromosomes, a larger content of DNA, a nuclear envelope, histones, a new principle of gene regulation, and so forth. The cell and molecular biology of only a small fraction of extant eukaryotes, but it is unlikely that any primitive eukaryotic cells have survived to give us insight into the origin of the eukaryotic cell line. Nevertheless, increased knowledge of the function and structure of contemporary eukaryotic cells may someday provide an indication of the origin and evolution of the eukaryotic cell.
Continued study of microfossils will no doubt result in more accurate estimates of the timing of such events as the origin of the first cells progenotes , the evolution of the prokaryote and eukaryote lines, and evolution of the first simple multicellular organisms from unicellular eukaryotes. Once the first cell had formed 3. We know little about the particular steps, such as the evolution of regulatory genes, the evolution of photosynthesis, the evolution of the first eukaryotic cell, or the evolution of those genetic mechanisms that made possible the first multicellular organisms.
Future research in molecular biology, genetics, and cell biology may yet give us a better idea of these processes of cellular evolution. However, we are faced with a conceptually far more difficult problem than cellular evolution, and that is the matter of how the cell came into existence in the first place. It is impossible to formulate any reasonable scheme by which a cell might have formed directly from the inorganic materials present on the primitive Earth.
The jump from inorganic chemicals to organic molecules capable of self-replication is simply too enormous. A solution to this conceptual dilemma was first proposed by the Russian biochemist, Alexander I. Oparin, and the British biologist J. Haldane beginning in the s, and is now generally called the organic soup concept.
The great contribution of Oparin and Haldane to the subject of the origin of life was based on the idea that in the period before life arose the atmosphere of Earth contained hydrogen H 2 , methane CH 4 , ammonia NH 3 , and water H 2 O , but no free oxygen O 2. Thus, Oparin and Haldane proposed that the pre-life atmosphere of Earth was highly reducing in a chemical sense.
From a variety of evidence, geologists, cosmologists, and chemists now generally agree that primitive atmosphere was chemically reducing in nature. As an example of these lines of evidence, early Precambrian rocks contain ferrous iron, which is unstable in the presence of O 2.
Therefore, the early Precambrian rocks must have been laid down in the absence of atmospheric O 2.
Oparin and Haldane both reasoned that a reducing atmosphere consisting of H 2 , CH 4 , NH 3 , and H 2 O would be favorable for the spontaneous formation of simple organic molecules and these might then polymerise spontaneously into macromolecules. These macromolecules might then accumulate in the oceans and lakes of the time, giving rise to organic soups. It is doubtful that the accumulation would have been great because many kinds of organic molecules are unstable in aqueous solutions and are slowly and spontaneously hydrolysed. However, one may suppose that organic molecules may have become concentrated by adsorption to solid surfaces a common phenomenon or through the rapid evaporation of lakes.
Fifteen years later, in , the Oparin-Haldane proposal about the spontaneous formation of organic molecules was tested directly. With the apparatus shown in Figure 1. Water was first added to the flask. The air was pumped out with a vacuum pump and the apparatus was then filled with a mixture of hydrogen, methane, and ammonia.
The electric discharges, which were common in the primitive atmosphere as lightning provided, energy for the synthesis of molecules from the four starting components. The water in the flask was boiled to cause circulation through the apparatus and remove any reaction products from the spark zone. Reaction products collected in the condensing water in the condenser and accumulated in the water phase. The experiment was run for one week, and the water then analysed for any organic compounds that might have formed.
A complicated mixture of small amounts of hundreds or even thousands of compounds is theoretically possible and might have reasonably been expected. Instead a small number of compounds accounted for most of the reaction products. Second, the molecules produced included several of major biological importance, particularly the amino acids glycine, alanine, aspartic acid, and glutamic acid.
Fifteen percent of the carbon added as CH 4 to the apparatus was recovered in the compounds identified in Table 1. Additional carbon was converted into unidentified, tarlike, high-molecular-weight, organic polymers. This experiment has been repeated with various modifications many times in other laboratories. In recent years radio-astronomy has provided evidence by microwave spectroscopy that abiological synthesis of large quantities of biologically important molecules occurs commonly in the universe outside the Earth.
This list is striking because it includes the very compounds that are the most important for the abiological synthesis of amino acids, purines, pyrimidines, and sugars. For example, formaldehyde, acetaldehyde, and hydrocyanic acid HCN react to form glutamic acid. Cyanoacetylene is a precursor of pyrimidines, and in particular can form a large amount of cytosine. Ribose, glucose, and other sugars are formed spontaneously in an alkaline solution of formaldehyde.
Hydrocyanic acid is a precursor of glycine and purines. A group of meteorites known as carbonaceous chondrites also contain organic molecules. The Murchison meteorite, which fell near Murchison, Australia in , contains two percent carbon, much of which is present as a complex mixture of organic molecules. Among these are glycine, alanine, valine, proline, glutamic acid, and aspartic acid. Similar findings have been made with the Murray meteorite, which fell in the U.