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Random in Biological Definition

Barr body

... This happens early in embryonic development at random in mammals , except in marsupials and in some ... passed on to daughter cells during mitosis. Since random chromosomes are selected for inactivation early ... important in chromosome counting: ensuring that random inactivation only takes place when two ...

Diffusion

... diffusion This is the process whereby the random thermally activated hopping of atoms in a ... be observable (). The direction of the motion is random and thus constantly changing. In principle, ... path of any given photon's path is effectively a random walk . The behavior of a large ensemble of ...

Genetic fingerprinting

... discriminating outcome, with the chance of a random match being in the 1 in a billion region. PCR is ... is not sound unless the suspect was drawn at random from the population of the country. In fact, a ... should be asked: Could it be an accidental random match? If not, could the DNA sample have been ...

Polymerase chain reaction

... in the primers used for the PCR program. random mutagenesis, on the other hand, is based on the ... polymerases in the PCR process. In the case of random mutagenesis, the location and nature of the mutations cannot be controlled. One application of random mutagenesis is to analyze structure-function ...

Artificial life

... create new "organisms" identical to itself, so long as there was a random pool of new boxcars to draw from. Edward F. Moore proposed "Artificial ... A Report from the Frontier Where Computers Meet Biology . Vintage Books: random House, New York. ISBN 0-679-74389-8 External links ...

Diabetes mellitus

... test varies according to circumstances and local policy and may be a random glucose, a fasting glucose and insulin, a glucose 2 hours after 75 g of ... two hours after a 75 g glucose load; or symptoms of diabetes and a random glucose above 11 mmol/l (200 mg/dl). While not used for diagnosis, ...

Ewens's sampling formula

... Ewens , states that under certain conditions (specified below), if a random sample of n gametes is taken from a population and classified ... that of the integer partition induced by a uniformly distributed random permutation . As the probability that no two of the n genes are the ...

Genetic drift

... over time. It is a stochastic effect that arises from the role of random sampling in the production of offspring . Like selection, it acts on ... in real populations are not probability distributions; rather, they are a random sample, and are thus subject to the same statistical fluctuations ...

Genetic recombination

... to each offspring. Even without recombination, each gamete contains a random assortment of chromatids, choosing randomly from each pair of chromatids available. With recombination, however, the gamete can receive a (mostly) random assortment of individual genes, as each chromosome may contain genetic ...

James D. Watson

... James D. Watson, Genes, Girls, and Gamow: After the Double Helix , random House, January, 2002, hardcover, 259 pages, ISBN 0375412832 James D. Watson and Andrew Berry, DNA: The Secret of Life , random House, April, 2003, hardcover, 464 pages, ISBN 0375415467 External ...

Patau syndrome

... syndrome. Most cases of Patau syndrome are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An ... cells. Mosaic Patau syndrome is also not inherited. It occurs as a random error during cell division early in fetal development. As a result, some ...

Secondary structure

... of the Myoglobin protein. alpha helices are shown in colour, and random coil in white, there are no beta sheets in shown. This protein was the ... of a protein includes alpha helices , beta sheets , turns , and random coil , among other less common structure. Such structures often can be ...

Y chromosome

... Chromosomes have robust and accurate repair mechanisms. Over time random mistakes - mutations - occur throughout all chromosomes, and the existence ... existed within this chromosome at all. Without any such machinery, random errors in copying would logically and inevitably cause the destruction and ...

Abiogenesis

... made since the Miller-Urey experiment , abiogenesis is under constant attack from creationists, who continually claim that the origin of life by random natural processes is so unlikely as to be, for all practical purposes, impossible." [2] The above link contains some articles that challenge ...

Ames test

... nutrients to grow. If the mutation screened for has in fact occurred dense spots in the colonies will form. A certain number of spots may form due to random mutation not caused by the agent; therefore, data analysis using control dishes is necessary. Occasionally a tested agent will be toxic enough to ...

Apoptosis

... fit with an astounding number of precise molecular shapes. This means that most of these immature cells can be either ineffective (because the almost random shapes of their receptors do not engage any antigen of significance), or dangerous to their own organism, because their receptors could make a good ...

Cell growth

... . However, in organisms with more than one set of chromosomes at the main life cycle stage, sex may also provide an advantage because, under random mating, it produces homozygotes and heterozygotes according to the Hardy-Weinberg ratio . Related articles Bacterial growth ...

Common descent

... years ago (see: origin of life ). History The first suggestion that all organisms may have had a common ancestor and diverged through random variation and natural selection was made in 1745 by the French mathematician and scientist Pierre-Louis Moreau de Maupertuis (1698-1759) in his ...

Digital organism

... at Los Alamos National Laboratory took the idea from Core War one step further in his core world system. He introduced mutations, in the form of random changes in the instructions of the programs inhabiting the core world. However, Rasmussen did not observe the evolution of complex and stable ...

Enzyme

... new enzymes than would having the functionally related amino acids of the active site widely dispersed throughout the amino acid chain, with random mutation occurring anywhere. Enzymes can couple two or more reactions, so that a thermodynamically favourable reaction can be used to "drive" a ...

Evolution

... in some alleles disappearing from the population. Two separate populations that begin with the same allele frequency might, therefore, "drift" by random fluctuation into two divergent populations with different allele sets (for example, alleles that are present in one have been lost in the other). ...

Fitness landscape

... of deliveries per hour on route s . The best, or at least a very good, solution is then found in the following way. Initially, a population of random solutions is created. Then, the solutions are mutated and selected for those with higher fitness, until a satisfying solution has been found. ...

Gamete

... produced through crossover (a form of genetic recombination ) of chromosomes, something that takes place in meiosis. This hybridization has a random element and the chromosomes tend to be a little different in every gamete an individual produces. This recombination, and the fact that the two ...

Hardy-Weinberg principle

... ) (also Hardy–Weinberg equilibrium ( HWE ), or Hardy–Weinberg law ) states that, under certain conditions, after one generation of random mating , the genotype frequencies at a single gene locus will become fixed at a particular equilibrium value. It also specifies that those ...

Kinetic energy

... to work in that it represents a change in internal energy . The energy that heat represents specifically refers to the energy associated with the random translational motion of atoms and molecules in some identifiable matter within a system . The conservation of heat and mechanical work form the ...

Life

... Urey-Miller experiment . Phospholipids spontaneously form lipid bilayers , the basic structure of a cell membrane . Procedures for producing random RNA molecules can produce " ribozymes ", which are able to produce more of themselves under very specific conditions. There are many different ...

Lynn Margulis

... , which challenges a central tenet of neodarwinism . She argues that inherited variation, significant in evolution, does not come mainly from random mutations. Rather new tissues, organs, and even new species evolve primarily through the long-lasting intimacy of strangers. The fusion of genomes in ...

Max Delbr

... Bruce, with whom he had four children. In 1942, he and Salvador Luria demonstrated that bacterial resistance to virus infection is caused by random mutation and not adaptive change. For that, they were awarded the Nobel Prize in Physiology or Medicine in 1969 , sharing it with Alfred ...

Memory

... long- and short-term memories is arbitrary, and is merely a reflection of differing levels of activation within a single store. If we are given a random seven-digit number, we may remember it only for a few seconds and then forget (short-term memory). On the other hand, we can remember telephone ...

Metapopulation

... of the other populations and eventually goes extinct as a consequence of demographic stochasticity (fluctuations in population size due to random demographic events); the smaller the population, the more prone it is to extinction. Although individual populations have finite life-spans, the ...

Molecular genetics

... organisms, such as yeast and mice , it is possible to induce the deletion of a particular gene, creating a gene knockout . Alternatives include the random induction of DNA deletions and subsequent selection for deletions in a gene of interest, the application of RNA interference and the creation of ...

Natural selection

... discoveries in genetics explain several mechanisms that occur in the process of reproduction: in the case of both asexual and sexual reproduction, random mutation (including DNA transcription errors); in the case of sexual reproduction (which mixes the DNA of two parents into an offspring), gene ...

Operator

... which may itself consist of vectors or functions , rather than just numbers. The expectation operator in probability theory , for example, has random variables as domain (and is also a functional ). To draw attention to the fact that the domain consists of pairs or tuples of some sort, in ...

Origin of life

... C. Urey in 1953 . Phospholipids spontaneously form lipid bilayers , the basic structure of a cell membrane . Procedures for producing random RNA molecules can produce " ribozymes ", which are able to produce more of themselves under certain specific conditions. The origin (see ...

Osmosis

... the use of table salt to kill leeches and slugs depends on osmosis. Chemical potential When a solute is dissolved in a solvent, the random mixing of the two species results in an increase in the entropy of the system, which corresponds to a reduction in the chemical potential. For the ...

Protein

... water . A protein that loses its native state is said to be denatured . Denatured proteins generally have no secondary structure other than random coil. A protein in its native state is often described as folded . One of the more striking discoveries of the 20th century was that the native ...

Red Queen

... arctic and white in order that the bear can stalk seals for food. For the first case the selection pressure is likely to be constant or subject to random change, in the second case the selection pressure is likely to increase steadily as selection for cautiousness in seals makes the average seal harder ...

Speciation

... ancestor) splits into two (or more) reproductively-isolated populations, each of which then accumulates changes from sexual reproduction and/or random mutation (in addition to any other various contributors to genetic change) until the populations are no longer capable of interbreeding ( ...

Symbiogenesis

... Species , Lynn Margulis argued that symbiogenesis was the primary force in evolution . According to her theory, acquisition and accumulation of random mutations are not sufficient to explain how inherited variations occur, and new organelles , bodies, organs , and species arise from ...
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