Portal:Biotechnology/Selected articles

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Selected articles of Portal:Biotechnology[edit]


Gel electrophoresis is a group of techniques used by scientists to separate molecules based on physical characteristics such as size, shape, or isoelectric point. Gel electrophoresis is usually performed for analytical purposes, but may be used as a preparative technique to partially purify molecules prior to use of other methods such as mass spectrometry, PCR, cloning, DNA sequencing, or immuno-blotting for further characterization.

The first part, "gel", refers to the matrix used to separate the molecules. In most cases the gel is a crosslinked polymer whose composition and porosity is chosen based on the weight and composition of the target of the analysis. When separating proteins or small nucleic acids (DNA, RNA, or oligonucleotides) the gel is usually made with different concentrations of acrylamide and a cross-linker, producing different sized mesh networks of polyacrylamide. When separating larger nucleic acids (greater than a few hundred bases), the preferred matrix is purified agarose (which is a seaweed extract). In both cases, the gel forms a solid but porous matrix that looks and feels like clear Jell-O. Acrylamide, in contrast to polyacrylamide, is a neurotoxin and needs to be handled using Good Laboratory Practices (GLP) to avoid poisoning.

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Escherichia coli

Escherichia coli, usually abbreviated to E. coli, discovered by Theodor Escherich, a pediatrician and bacteriologist, is one of the main species of bacteria that live in the lower intestines of warm-blooded animals, including birds and mammals. They are necessary for the proper digestion of food and are part of the intestinal flora. Its presence in groundwater is a common indicator of fecal contamination. The name comes from its discoverer, Theodor Escherich. It belongs among the Enterobacteriaceae, and is commonly used as a model organism for bacteria in general. One of the root words of their family's scientific name, "enteric", refers to the intestine, hence "gastroenteritis" (from 'gastro-', stomach, 'entero-' intestine, '-itis', disease). "Fecal" is the adjective for organisms that live in feces, so it is often used synonymously with "enteric".

The number of individual E. coli bacteria in the feces that one human passes in one day averages between 100 billion and 10 trillion. All the different kinds of fecal coli bacteria and all the very similar bacteria that live in the ground (in soil or decaying plants, of which the most common is Enterobacter aerogenes are grouped together under the name coliform bacteria. Technically, the "coliform group" is defined to be all the aerobic and facultative anaerobic, non-spore-forming, Gram-negative, rod-shaped bacteria that ferment lactose with the production of gas within 48 hours at 35°C (95°F). In the body, this gas is released as flatulence).

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Entire and hydrolised lactose

The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. It consists of three adjacent structural genes, a promoter, a terminator, and an operator. The lac operon is regulated by several factors including the availability of glucose and of lactose. Gene regulation of the lac operon was the first genetic regulatory mechanism to be elucidated and is often used as the canonical example of prokaryotic gene regulation.

The lac operon consists of three structural genes, a promoter, a terminator, and an operator. The three structural genes are: lacZ, lacY, and lacA. lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose. lacY encodes β-galactoside permease (LacY), a membrane bound transport protein that pumps lactose into the cell. lacA encodes β-galactoside transacetylase (LacA), an enzyme that transfers an acetyl group from acetyl-CoA to β-galactosides. Only lacZ and lacY appear to be necessary for lactose catabolism.

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Dr. Venter (right) on his visit in Hong Kong in December 2004

John Craig Venter (born October 14, 1946, Salt Lake City) is an American biologist and businessman. He began his academic career at a community college, College of San Mateo (California), after enlisting in the navy and serving a tour of duty during the Vietnam War. On returning, he received his bachelor's degree in biochemistry in 1972, and his Ph.D. in physiology and pharmacology in 1975, both from the University of California, San Diego. After working at the University at Buffalo, The State University of New York, he joined the National Institutes of Health in 1984.

While at NIH, Venter learned of a technique for rapidly identifying all of the mRNAs present in a cell, and began to use it to rapidly identify human brain genes. The short cDNA sequence fragments discovered by this method are called Expressed sequence tags, or ESTs, a name coined by Anthony Kerlavage at The Institute for Genomic Research. In a controversial court case, Venter tried to patent these gene fragments and lost the case.

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Dolly (5 July 1996 – 14 February 2003), a ewe, was the first mammal to have been successfully cloned from an adult cell. She was cloned at the Roslin Institute in Scotland and lived there until her death when she was 6. Her birth was announced on 22 February 1997.

The sheep was originally code-named "6LL3". The name "Dolly" came from a suggestion by the stockmen who helped with her birth, in honour of Dolly Parton, because it was a mammary cell that was cloned[1]. The technique that was made famous by her birth is somatic cell nuclear transfer, in which a cell is placed in a de-nucleated ovum, the two cells fuse and then develop into an embryo. When Dolly was cloned in 1996 from a cell taken from a six-year-old ewe, she became the centre of much controversy that still exists today.

On 9 April 2003 her stuffed remains were placed at Edinburgh's Royal Museum, part of the National Museums of Scotland.

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Mouse embryonic stem cells.

Stem cells in animals are primal undifferentiated cells that retain the ability to divide and differentiate into other cell types. In higher plants this function is the defining property of the meristematic cells. Stem cells have the ability to act as a repair system for the body, because they can divide and differentiate, replenishing other cells as long as the host organism is alive.

Medical researchers believe stem cell research has the potential to change the face of human disease by being used to repair specific tissues or to grow organs. Yet there is general agreement that, "significant technical hurdles remain that will only be overcome through years of intensive research."[1]

The study of stem cells is attributed as beginning in the 1960s after research by Canadian scientists Ernest A. McCulloch and James E. Till.

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A mug of golden lager beer

Beer is an alcoholic beverage produced through the fermentation of cereal sugars, and which is not distilled after fermentation. The unfermented sugar solution, called wort, is obtained from steeping, or "mashing," malted cereal grains, usually barley. Alcoholic beverages made from the fermentation of sugars derived from non-grain sources — fruit juices or honey, for example — are generally not called "beer," despite being produced by the same yeast-based biochemical reaction.

The process of beer production is called brewing. Brewing dates back to at least the 5th millennium BC (prior even to writing), and is recorded in the written history of Ancient Egypt and Mesopotamia.

Because the ingredients and procedures used to make beer can differ, beer characteristics such as taste and colour may also vary. While local names for beers made with the same methods and ingredients may vary, the similarities of method and ingredients can be detected to form a study of the nature of beer styles.

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Agrobacterium tumefaciens galls

Agrobacterium tumefaciens is a species of bacteria that causes tumors (commonly known as 'galls' or 'crown galls') in dicots (Smith et al., 1907). This Gram-negative bacterium causes crown gall by inserting a small segment of DNA (known as the T-DNA, for 'transfer DNA') into the plant cell, which is incorporated at a semi-random location into the plant genome.

Agrobacterium is an alpha proteobacterium of the family Rhizobiaceae, which includes the nitrogen fixing legume symbionts. Unlike the nitrogen fixing symbionts, tumor producing Agrobacterium are parasitic and do not benefit the plant. The wide variety of plants affected by Agrobacterium makes it of great concern to the agriculture industry (Moore et al., 1997).

Note that Agrobacterium is not the only or most common source of galls on plants. Many are caused by insect larvae that secrete plant growth hormones and have the same effect.

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DICER protein

Small interfering RNA (siRNA), are a class of 20-25 nucleotide-long RNA molecules that play a variety of roles in biology. Most notably, this is the RNA interference pathway (RNAi) where the siRNA interferes with the expression of a specific gene. While this article largely deals with siRNAs in the RNAi pathway, it should be noted that siRNAs play additional roles in RNAi-related pathways, e.g. as an antiviral mechanism or in shaping the chromatin structure of a genome; the complexity of these pathways is only now being elucidated. SiRNAs were first discovered by David Baulcombe's group in Norwich, England, as part of post-transcriptional gene silencing (PTGS) in plants[2]. Shortly thereafter, in 2001, synthetic siRNAs were then shown to able to induce RNAi in mammalian cells by Thomas Tuschl and colleagues[3]. This discovery led to a surge in interest in harnessing RNAi for biomedical research and drug development.

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A handful of compost

Compost is the decomposed remnants of organic materials (those with plant and animal origins, see compostable). Compost is used in gardening and agriculture, mixed in with the soil. It improves soil structure, increases the amount of organic matter, and provides nutrients. Biodegradation is the means by which organic matter is recycled in its environment (see composting).

Compost is a common name for humus, which is the result of the decomposition of organic matter. Decomposition is performed primarily by microbes, although larger creatures such as nematode and oligochaete worms (see vermicomposting), and ants, contribute to the process. Decomposition occurs naturally in all but the most hostile environments, such as buried in landfills or in extremely arid deserts, which prevent the microbes and other decomposers from thriving.

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Cloning diagram

Cloning is the process of creating an identical copy of an original. A clone in the biological sense, therefore, is a single cell (like bacteria, lymphocytes etc.) or multi-cellular organism that is genetically identical to another living organism. Sometimes this can refer to "natural" clones made either when an organism reproduces asexually or when two genetically identical individuals are produced by accident (as with identical twins), but in common parlance the clone is an identical copy by some conscious design. Also see clone (genetics). The term clone is derived from κλων, the Greek word for "twig". In horticulture, the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o". Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively.

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Golden rice is a variety of rice (Oryza sativa) produced through genetic modification to biosynthesise of the precursors of beta-carotene (pro-vitamin A) in the edible parts of rice. The scientific details of the rice were first published in Science in 2000.1 Golden rice was developed as a fortified food to be used in areas where there is a shortage of dietary Vitamin A. In 2005, a new variety called golden rice 2 was announced, it produces up to 23 times more beta-carotene than the original variety of golden rice.2 Neither variety is available for human consumption.

Although golden rice was developed as a humanitarian tool it has met with significant opposition from environmental and anti-globalization activists.

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More selected articles[edit]

Now, there are 12 selected articles, but in the future could be more (one for each week). Meanwhile, we can list these articles here: