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Frequency in Biological Definition

Allele frequency

... Allele frequency is a term of population genetics that is used ... the richness of its gene pool . Allele frequency is defined as follows: Given a) a particular ... variant or allele of the gene, then the allele frequency of that allele is the fraction or percentage of ...

Evolution

... been defined more specifically as a change in the frequency of alleles in a population from one generation ... synthesis, "evolution" means a change in the frequency of an allele within a gene pool . This change ... create new alleles , other factors influence the frequency of existing alleles. These factors mean that some ...

Genetic drift

... selection, it acts on populations , altering the frequency of alleles and the predominance of traits ... in a breeding population, if an allele has a frequency of p , probability theory dictates that (if ... parents the next one only once. Therefore the frequency of an allele among the offspring often differs ...

Hardy-Weinberg principle

... haploid for that gene. So the genotype frequency at equilibrium is therefor p and q for the ... is caused by an X-linked recessive allele. The frequency in males is about 1 in 12, (or 0.083) whereas it ... different allele frequencies, then the allele frequency of the male population follows that of the female ...

Molecular evolution

... 2.1 Mutations 2.2 Causes of change in allele frequency 2.3 Molecular study of phylogeny 2.4 The ... theory. Causes of change in allele frequency Main article: Population genetics There ... of a characteristic; or, more specifically, the frequency of an allele (variant of a gene ): ...

Magnetic resonance imaging

... a temporary non-aligned high-energy state. The frequency of the pulses is governed by the Larmor Equation ... memory termed K-space ; this is the spatial frequency weighting in two or three dimensions of a real ... fields and non-ionizing radiation in the radio frequency range. Compare this to CT scans and ...

Wavelength

... λ has an inverse relationship to frequency f , the number of peaks to pass a point in a ... to the speed of the wave type divided by the frequency of the wave. When dealing with electromagnetic ... sound in air = 343 m/s at 20 C (68 F) f = frequency of the wave For radio waves this relationship ...

Absorption spectrum

... of energy. Using E = hf , a photon's energy is directly related to its frequency (and hence its wavelength). Only those wavelengths that correspond to a ... higher orbit and falls back down, emitting a photon of exactly the same frequency as the one absorbed. However, this is emitted in all directions, not just ...

Genetic recombination

... However, there is an exception that requires further discussion. The frequency of recombination is actually not the same for all gene combinations. This ... The nicks are then removed by ligases . See also recombinant frequency References Alberts, B. et al., Molecular Biology of the Cell , ...

Microsatellite

... hypervariability arises because the repeated simple sequences cause a high frequency of loss or insertion of additional repeats by confusing the DNA ... be damaged, microsatellites may be gained or lost at an especially high frequency during each round of mitosis . Hence a tumour cell line might show a ...

Photon

... radiation that can exist is one photon whatever its wavelength , frequency , energy , or momentum . Photons are fundamental particles . Their ... by the equation: where ( lambda ) is the wavelength f is the frequency (the symbol ( nu ) is often used instead, but f is used here to avoid ...

Blood type

... Rare phenotypes 4.1 Bombay phenotype 5 Compatibility 6 frequency 7 Other blood types 8 Social significance 9 References ... O- X frequency Blood types are not evenly distributed throughout the human population. ...

Bacterial conjugation

... recipients DNA by recombination. Bacteria with an integrated F-plasmid do recombine unusually often, which is why they are also called Hfr- (high frequency recombination-) strains . See also biology genetics plasmid ...

Biomechanics

... of muscles: Skeletal Muscle (striated) Unlike cardiac muscle, skeletal muscle can develop a sustained condition known as tetany through high frequency stimulation, resulting in overlapping twitches and a phenomenon known as wave summation. At a sufficiently high frequency, tetany occurs, and the ...

Chromosomal crossover

... over was first demonstrated by Harriet Creighton and Barbara McClintock in 1931 . See also Genetic recombination Recombinant frequency ...

Computed axial tomography

... scans are adequate. For evaluation of chronic interstitial processes ( emphysema , fibrosis , and so forth), thin sections with high spatial frequency reconstructions are used. For evaluation of the mediastinum and hilar regions for lymphadenopathy , IV contrast is administered. CT angiography ...

DNA

... per 10 bp of sequence. This is also the approximate length of sequence in which the double helix makes one complete turn about its axis. This frequency of twist (known as the helical pitch ) depends largely on stacking forces that each base exerts on its neighbors in the chain. Supercoiled ...

Enzyme

... position the active regions correctly. Because the precise structure of each region tends to be fairly critical to correct function, and because the frequency of a mutation which would produce a nonfunctional active region is proportional to the length of the chain separating the amino acids involved, ...

Hfr cell

... called hfr strain ) is a bacterium with a conjugative plasmid (often F ) integrated into its genomic DNA. Hfr is the abbreviation for high frequency recombination . Unlike a normal F+ cell, hfr strains will, upon conjugation with a F- cell, attempt to transfer their entire DNA through the pilus ...

Major histocompatibility complex

... invoke balancing selection , a broad term which identifies any kind of natural selection in which no single allele is absolutely most fit. frequency dependent selection and heterozygote advantage are two types of balancing selection that have been suggested to explain MHC allelic diversity. ...

Natural selection

... Selection (computer game) . Natural selection is the primary mechanism within the scientific theory of evolution , i.e. it alters the frequency of alleles within a population . After a century of obscure and vague preliminary formulations, it was proposed as the main mechanism of ...

Plasmid

... are mobilisable , and carry only a subset of the genes required for transfer. These plasmids can 'parasitise' another plasmid, transferring at high frequency in the presence of a conjugative plasmid. Figure 4 : Schematic drawing of bacterial conjugation. 1 Chromosomal DNA . 2 Plasmids . 3 ...

Sociobiology

... be problematic, because a simple statistical correlation can be open to charges of circularity. Circularity can occur if the measurement of gene frequency indirectly uses the same measurements that describe the strategy. Though difficult, this overall process finds favour. As a successful example, ...

Synapse

... of a synapse may in effect diminish as a train of action potentials arrive in rapid succession--a phenomenon that gives rise to the so-called frequency dependence of synapses. The nervous system exploits this property for computational purposes, and apparently tunes its synapses through such means ...

Thomas Hunt Morgan

... about genes and their location on chromosomes helped transform biology into an experimental science." The centimorgan , a unit of recombinant frequency used in gene mapping, was named in his honor. External links http://www.columbia.edu/cu/alumni/Magazine/Morgan/morgan.html Thomas ...

Vestibular system

... humans, the time constants T 1 and T 2 are approximately 3 msec and 5 sec, respectively. As a result, for typical head movements, which cover the frequency range of 0.1 Hz and 10 Hz, the deflection of the cupula is approximately proportional to the head-velocity (!). This is very useful, since the ...

Optical spectrum

... could be detected - the presence of planets was revealed by their gravitational influence on the motion of the stars analysed. See also frequency Wavelength Rydberg formula Tetrachromat Trichromat ...

X-ray crystallography

... crystalline structure, the photons are diffracted by corresponding electrons in many symmetrically arranged molecules. Because waves of the same frequency whose peaks match reinforce each other, the signal becomes detectable. To determine a structure, one must first grow crystals of the molecule of ...

Y chromosome

... previously observed on a small scale over long evolutionary timescales between repeated sequences on the same chromosome, but not at the dramatic frequency apparently employed by the Y chromosome. A research team, led by David C. Page, M.D., a Howard Hughes Medical Institute investigator at the ...
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