number

Y chromosome

...esearchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. The Y chromosome likely contains between 70 and 300 genes. Because only males have ...

Xylem

...ions, such as nitrate , although it can contain a number of organic chemicals as well. Mechanism Xylem sap always moves from the roots to the leaves . It travels by bulk flow , like water in a series of pipes, rather than by diffusion through cells. Two phenomena cause xylem sap to flow: The soi...

X chromosome

...esearchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. The X chromosome likely contains between 900 and 1,200 genes. Genes on chromosome ...

Astrobiology

...relevance to xenobiologists. Some contend that the number of planets with intelligent extraterrestrial life can be estimated from the Drake equation if and when we ascertain the values of its variables. However uncertainties in the term of the equation make it impossible to predict whether life is rare or...

Wobble base pair

... The genetic code makes up for disparities in the number of amino acids (20) for codons (64) by using modified base pairs in the first base of the anti-codon. One important modified base is inosine which can basepair with three bases including uracil , adenine , and cytosine . Another critical bas...

Wavelength

...as an inverse relationship to frequency f , the number of peaks to pass a point in a given time. The wavelength is equal to the speed of the wave type divided by the frequency of the wave. When dealing with electromagnetic radiation in a vacuum, this speed is the speed of light c , for signals (wave...

Vitamin

...sential amino acids . Nor is it used for the large number of other nutrients that are merely health-furtheri...s , scientists were able to isolate and identify a number of vitamins by depriving animals of them. Human vitamins Vitamin name Water/fat soluble ...

Virus

...ure from multiple copies of a single protein. The number of proteins required to form a spherical virus capsid is denoted by the 'T-number' whereby 60t proteins are necessary. In the case of hepatitis B virus the T-number is 4, therefore 240 proteins assemble to form the capsid. As in the helical viruses...

Yellow fever

...ol methods have proved effective in decreasing the number of cases. Treatment There is no specific cure ...nch company) were thwarted in part due to the huge number of deaths amongst workers caused by the Yellow Fever. The vaccination for the fever was first formul...

Varicella zoster virus

...ochlorite . Within the body it can be treated by a number of drugs and therapeutic agents including aciclovir , zoster immunoglobulin (ZIG), and vidarabine . A live attenuated VZV Oka/Merck strain vaccine is available and is marketed under the trade name Varivax . It was developed by Merck, Sharp &...

Vacuole

... big vacuole is the most common case, the size and number of vacuoles may vary in different tissues and stages of development. Cambium cells, for example, have many small vacuoles in winter, and a large one in summer. The central vacuole's main role (besides being a storage center) is to keep a turgor ...

Vaccine

...is used in the United States very infrequently. A number of innovative vaccines are also in development and... vaccination campaigns: [2] . Prior to 1997 , a number of vaccines, including those given to very young children, used thimerosal , a preservative that me...

Tumor

...ot enough for a tumor to occur. A combination of a number of mutations is necessary. DNA microarrays can be used to determine if oncogens or tumor repressor gens have been mutated. Possibly in the future tumors can be treated better by using DNA microarrays to determine the exact characteristics of the ...

Transformation

...hout limit. Normal cells can divide only a certain number of times before they will stop dividing. Cells that have been transformed no longer have such a limit (for example, cancer cells) are able to grow and divide potentially forever. In mathematics , a transformation is any of a variety of differe...

Tobacco mosaic virus

...ncluding tobacco, tomato, pepper, cucumbers, and a number of ornamental flowers. There are many different strains. External links Electron microscope image of TMV Several EM images and schematic drawings Images of the TMV coat protein...

Tobacco mosaic virus

...ncluding tobacco, tomato, pepper, cucumbers, and a number of ornamental flowers. There are many different strains. External links Electron microscope image of TMV Several EM images and schematic drawings Images of the TMV coat protein...

Thomas Malthus

...considered an economic plus since it increased the number of workers available to the economy. Malthus, however, looked at fertility from a new perspective and convinced most economists that even though high fertility might increase the gross output it tended to reduce output per capita. Many 20th century ...

Thermoregulation

...erature regulation In addition to human beings, a number of animals also maintain their body temperature by physiological and behavioral adjustments. For example, a desert lizard alters their location continuously during a day. In the morning, some portion of its body, which is head, emerges from its burro...

Systems biology

... and in fact are now becoming a reality as a small number of forward-thinking biotechnology companies are using this cell-biology driven approach to the development of next-generation therapeutics. However, these predictions rely upon our ability to understand and quantify the roles that specific genes pos...

Synapse

...osphorylation of the proteins involved. The size, number and replenishment rate of vesicles also are subject to regulation, as are many other elements of synaptic transmission. The drugs known as selective serotonin re-uptake inhibitors or SSRIs affect certain synapses by inhibiting the re-uptake of the ...

Stoma

...ly, upper epidermis is directly illuminated. Less number of stomata on the upper epidermis can then prevent...eaves are held vertically, they will have the same number of stomata on the two epidermis. If the plant has floating leaves, there will be no stomata on the ...

Stem cell

...ng the course of a lifetime. However, there are a number of clinically proven adult stem cell successes. ...er for older people. Although normally scarce, the number of peripheral blood cells can be increased by a course of drugs, which release the stem cells from...

Spliceosome

...have been used to account for the relatively small number of genes in the human genome . For years the estimate was 100,000 genes, but now, thanks to the Human Genome Project we know the figure is closer to 30,000 genes. However, almost every human gene is thought to have at least two isoforms . S...

Species

...tions , not individual organisms, and that a small number of exceptional individuals within a population may...y comparing the colour of flowers, bark, and buds, number of flowers for a given size of tree, and the shape of the leaves and fruit. When using a combinatio...

Sociobiology

...y pointed out that Wilson had personally adopted a number of liberal political stances and had attracted progressive sympathy for his outspoken environmentalism . They argued that as scientists they had a duty to uncover the "truth" whether that was politically correct or not. They argued that sociobio...

Skin

...The dermis lies below the epidermis and contains a number of structures including blood vessels, nerves, hair follicles, smooth muscle , glands and lymphatic tissue . It is made up of dense connective tissue - collagen , elastin and reticular fibres are present. Erector muscles, attached betw...

Signal transduction

...on. In many transduction processes, an increasing number of enzymes and other molecules become engaged in t...e by phosphorylation ; also, the variation of the number of receptors can vary the total signal strength in the recipient cell. Signal transduction of tr...

Rudolf Steiner

...ous theatres throughout the world. There are now a number of Eurythmy schools where a full four-year trainin...nds of copies. Today around the world there are a number of innovative banks, companies, charitable institutions, and schools for developing new cooperative ...

Redox

...all processes in which atoms have their oxidation number (oxidation state) changed.This can be a simple re... → 2F - Elements always have an oxidation number of zero. In the first half reaction hydrogen is oxidized from an oxidation number of zero to an oxid...

Pyrimidine

... 20 - 22 C Boiling point 123 - 124 C CAS number 289-95-2 SMILES C1=NC=NC=C1 Pyrimidine is a heterocyclic aromatic organic compound , which is similar to benzene and pyridine and that contains two nitrogen atoms at positions 1 and 3 of the six-membered ring. Three n...

Purine

...s 120.11 g/mol Melting point 214 C CAS number 120-73-0 SMILES C1(NC=N2)=C2C=NC=N1 ...components of DNA and RNA, and are also found in a number of other important biomolecules, such as ATP , GTP , cyclic AMP , NADH , and coenzyme A . ...

Pseudopod

...cytosis . Phagocytosis pseudopods have arisen in a number of different protist groups, but also in some cells ( phagocytes ) in multicellular organisms. Morphology Pseudopods can be classified into several varieties according to their appearance: Lobopodia are bulbous, short and blunt in form, ve...

Proteomics

...Bank External link MIT - Reduction in the number of human genes from previous estimates. Proteomic World - Resources for proteomics research. Yeast GFP Localization Database - Database of microscope images and quantitation for most of the yeast proteome. References Twyman, R. M. 2004....

Protein biosynthesis

...n of disulfide bridges or attachment of any of a number of biochemical functional groups , such as acetate , phosphate , various lipids and carbohydrates . Enzymes may also remove one or more amino acids from the leading (amino) end of the polypeptide chain, leaving a protein consisting of two pol...

Prion

...ommonly accepted that prions are responsible for a number of previously known but little-understood diseases generally classified under transmissible spongiform encephalopathy diseases (TSEs) , including scrapie (a disease of sheep ), kuru (found in members of the cannibalistic For tribe in Papu...

Primer

...primers and their melting temperature depends on a number of considerations. The melting (or annealing) temp...erature (T M ) of primers. (A, G, C and T are the number of nucleotides in the primer, respectively. [Na + ] is the concentration of Na + in the PCR vial.) ...

Potential energy

...ing about potential energy is that you can add any number to all points in space and it doesn't affect the p...ber, positive or negative, but it must be the same number for all points] then the work done going from as before. In practical terms, this means that...

Population

...cies . Population density is a measure of the number of people or organisms per unit of area. Variants may express the population per unit of habitable, inhabited, productive (or potentially productive), or cultivated area. A particular geographic area of land is said to have a carrying capacity , r...

Plant

...into many different land environments. They have a number of adaptations that allowed them to overcome the l...nd are an important source of building material. A number of plants are used decoratively, including a variety of flowers . Growth Simple plants like alg...

Plant

...into many different land environments. They have a number of adaptations that allowed them to overcome the l...nd are an important source of building material. A number of plants are used decoratively, including a variety of flowers . Growth Simple plants like alg...

Photon

... i the possible momenta of the modes and the number of photons in this mode. Molecular absorption A typical molecule , M , has many different energy levels . When a molecule absorbs a photon, its energy is increased by an amount equal to the energy of the photon. The molecule then enters an ...

Polymerase chain reaction

...check for errors) and can significantly reduce the number of mutations that occur in the copied DNA sequence...rs and their melting temperature (Tm) depends on a number of considerations. The melting temperature of a primer--not to be confused with the melting temperat...

Patau syndrome

...ng in a mixed population of cells with a differing number of chromosomes, such cases are called Mosaic Patau... can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 13. If one of...

Parasitology

...ies has its own unique species of parasite, so the number of parasitic species greatly exceeds the number of free living species. Contents showTocToggle("show","hide") 1 Fields 1.1 Medical...

Paleontology

...ogist Jarmila Kukalova-Peck . History includes a number of prominent paleontologists. Charles Darwin collected fossils of South American mammals during his trip on the Beagle and examined petrified forests in Patagonia. Thomas Jefferson took a keen interest in mammoth bones. Besides looking at mammal ...

Redox

...all processes in which atoms have their oxidation number (oxidation state) changed.This can be a simple re... → 2F - Elements always have an oxidation number of zero. In the first half reaction hydrogen is oxidized from an oxidation number of zero to an oxid...

Outbreak

...s infection control measures and a relatively high number of infections are observed where no cases or spora...urring in a region), epidemic (an unusually high number of cases in a region), or pandemic (a global epidemic). Major human epidemic viruses include inf...

Operator

...operators Operators are described usually by the number of operands: monadic or unary operators tak...ry/tertiary operators take three arguments. The number of operands is also called the arity of the operator. If an operator has an arity given as n -a...

Olfaction

...s; the other genes have nonsense mutations . This number was determined by analyzing the genome in the Human Genome Project ; the number may vary among ethnic groups, and does vary among individuals. For example, some people can smell am...

Nutrition

...ctly regulated and all waste must be analyzed. The number of active variables involved in this type of experimentation is very high. This makes scientifically valid nutritional study very time consuming which accounts for why a proper science of human nutrition is rather new. History and recent dev...

Nucleon

...he components of an atom 's nucleus . The total number of nucleons in an atom is the mass number on the atom, as nucleons each have a mass very close to one amu . See also List of partic...

Neutral theory of molecular evolution

...e of human families. The test compares the actual number of differences between two sequences and the number that the neutral theory predicts given the independently estimated divergence time. If the actual nu...

Natural selection

... twenty years, he shared it with only a very small number of acquaintances, while he amassed evidence in its favor. In 1858, Alfred Russel Wallace independently discovered the principle, and wrote a letter to Darwin, explaining his hypothesis. This prompted a reading, at the Linnean Society , of tracts f...

Mutagen

...lly DNA ) of an organism and thus increases the number of mutations above the natural background level. Mutagens are usually chemical compounds or radiation . The Ames test is one method to determine how mutagenic an agent is. See also DNA repair Genetics Teratogen...

Muscle

...scle has been implicated to play a role in a large number of diseases affecting blood vessels , the respiratory tract (e.g. asthma ), the digestive system (e.g. irritable bowel syndrome ) and the urinary tract (e.g. urinary incontinence ). These disease processes are not usually confined to the mu...

Antibiotic resistance

...at patterns of antibiotic usage greatly affect the number of resistant organisms which develop. Overuse of broad-spectrum antibiotics , such as second and third generation cephalosporins , greatly hastens the development of methicillin resistance, even in organisms that have never been exposed to the sele...

Monoclonal antibody

...e sufficiently diluted and grown, thus obtaining a number of different colonies, each producing only one type of antibody. The antibodies from the different colonies are then tested for their ability to bind to the antigen (for example with a test such as ELISA ), and the most effective one is picked out. ...

Molecular evolution

...comparing their DNA, deduces elapsed time from the number of differences. The technique was inspired by the ...they assumed first, that there were a large enough number of alleles so that any mutation would lead to a different allele (that is the probability of back ...

Mitochondrion

...s hundreds or thousands of mitochondria. The exact number of mitochondria depends on the cell's level of met...thesis ). This nonchromosomal DNA encodes a small number of mitochondrial peptides (13 in humans) that are integrated into the inner mitochondrial membrane, ...

Mitochondrion

...s hundreds or thousands of mitochondria. The exact number of mitochondria depends on the cell's level of met...thesis ). This nonchromosomal DNA encodes a small number of mitochondrial peptides (13 in humans) that are integrated into the inner mitochondrial membrane, ...