Migration

The migration of different cell types, such as leucocytes and tumour cells, involves cellular strategies to overcome the physical resistance of three-dimensional tissue networks, ...
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Branch migration in naked DNA
From bacteria transformed with circular plasmids, one can isolate figure 8 type molecules.
Electron microscopy of these DNAs restricted at low temperatures reveals half chiasma (above).
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Migration is often an important density-dependent factor in reducing populations. As the population increases, many of its members emigrate.
Predation ...
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Migration
Movement of individuals between otherwise reproductively isolated populations.
Related Terms: Population ...
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Migration into or out of a population can breakdown genetic differences between populations. Mutations developing in one population may be spread to other populations by migration. This serves, like mutation, to introduce new alleles into populations.
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Migration patterns
Evolutionarily stable mitochondrial DNA and Y chromosomes have allowed bioanthropologists to begin to trace human migration patterns around the world and identify family lineages. An example:
Native Americans ...
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migration A seasonal movement from one location to another.
Milankovitch cycles Periodic variations in tilt, eccentricity, and wobble in the earth's orbit; Milutin Milankovitch suggested that it is responsible for cyclic weather changes.
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Emigration. The departure of individuals from a given area
Endosymbiotic. Being symbiotic and living within the body of an individual of the associated species ...
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Emigration moving out of a location
(e- = out; migrare = to move depart)
Empedocles person who lived around 490 to 444 BC and thought there were four original elements: Earth Air Fire and Water ...
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Immigration and emigration are present, but are usually not measured.
All of these are measured to determine the Harvestable surplus, which is the number of individuals that can be harvested from a population without affecting long term stability, ...
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the migration of individual cells from surface layers into the interior of the embryo.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ...
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Human Migration Hypotheses
Most scientists agree that an early hominid species evolved in Africa and spread across the Old World.
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Branch migration
A "zipper-like" pairing of two homologous DNA strands during genetic recombination.
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In 1924, the Immigration Restriction Act was passed, with eugenicists for the first time playing a central role in the Congressional debate, as expert advisers on the threat of "inferior stock" from Eastern and Southern Europe.
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Law -- the concept that both gene frequencies and genotype frequencies will remain constant from generation to generation in an infinitely large, interbreeding population in which mating is at random and there is no selection, migration or mutation.
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Modern historians now acknowledge that this presents an incomplete portrait of a complex time of migration.
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Differentiation between subpopulations, followed by migration among them, could contribute to adaptations amongst populations. Wright also came up with the idea of the adaptive landscape -- an idea that remains influential to this day.
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The loss or gain of alleles from a population due to the emigration or immigration of fertile individuals, or the transfer of gametes, between populations.
gene pool
The total aggregate of genes in a population at any one time.
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volvo - to roll]. A process of cellular migration involving movement of a sheet of cells over an edge and then spreading inwards in the opposite direction. This occurs, for example, during amphibian gastrulation.
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Another alternative is to migrate south in the winter, like birds do. Reptiles and amphibians are few or absent because of the extremely cold temperatures. Because of constant immigration and emigration, the population continually oscillates.
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centriole: a cylinder-like organelle that assists in chromosomal migration during mitosis.
centromere: the place of attachment of the two homologous chromatids during prophase in mitosis.
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: In an infinitely large population, gene and genotype frequencies remain stable as long as there is no selection, mutation, or migration. For a bi-allelic locus where the gene frequencies are p and q: p2+2pq+q2 = 1 (
Online HWE Analysis
; ...
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PULSED-FIELD GEL ELECTROPHORESIS (PFGE) - Separation of large (>50 kb) pieces of DNA, including complete chromosomes and genomes, by rapidly alternating the direction of electrophoretic migration in agarose gels.
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A complete break in the DNA puts the plasmid in a linear form. Supercoils, relaxed circular DNA, and linear DNA all have different migration properties in agarose gels, even though they contain the same number of base pairs.
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cointegrate An intermediate in the migration of certain DNA transposons in which the donor DNA and target DNA are covalently attached.
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