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Ratchet

ratchet

1. A pawl, click, or detent, for holding or propelling a ratchet wheel, or ratch, etc.

2. A mechanism composed of a ratchet wheel, or ratch, and pawl. See Ratchet wheel, below, and 2d Ratch. Ratchet brace, a circular wheel having teeth, usually angular, with which a reciprocating pawl engages to turn the wheel forward, or a stationary pawl to hold it from turning backward.

In the cut, the moving pawl c slides over the teeth in one direction, but in returning, draws the wheel with it, while the pawl d prevents it from turning in the contrary direction.

Origin: Properly a diminutive from the same word as rack: cf. F. Rochet. See Ratch, Rack the instrument.


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Re: Camouflage in nature

... that will increase survival and reproduction, RELATIVE TO OTHER MEMBERS OF THE BUG POPULATION that are all competing for not getting eaten, will ratchet through successive generations towards perfection, which nothing ever actually reaches. Survival of the fittest (greenest). Another factor, ...

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by Gavin
Sat Nov 12, 2011 3:34 pm
 
Forum: Evolution
Topic: Camouflage in nature
Replies: 16
Views: 12679

Recombination in RNA viruses,Ruzic,Kovac

... the removal of deleterious genes (for a review see Hurst & Peck, 1996). This second explanation is often linked to the notion of `Muller's ratchet ' ± the random loss of those individuals in a population having the fewest deleterious alleles (Muller, 1964). Muller's ratchet predicts the ...

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by anakovacevic
Sat Jun 12, 2010 8:28 pm
 
Forum: Cell Biology
Topic: Recombination in RNA viruses,Ruzic,Kovac
Replies: 2
Views: 35270

The Hitchhiking Gene

... and so avoid separation by chromosomal crossovers. While very rare, it does also apply to the non-recombinational sex Y chromosome. Thus, Muller's ratchet still holds true for sexually reproductive societies. Hitchhiking could pose a real problem for Evolution by natural selection if the deleterious ...

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by Morphoeclectic
Fri May 02, 2008 2:07 pm
 
Forum: Genetics
Topic: The Hitchhiking Gene
Replies: 0
Views: 2537

The Fiber Disease

... 20 nm. The thin and thick filaments are interdigitated and upon muscle contraction, the thick filaments are pulled along the thin filaments in a ratchet-like mechanism. Linear motion is achieved by the myosin head, which is attached to the thick filament via flexible hinge and binds to the actin ...

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by Nadas Moksha
Fri Oct 27, 2006 9:34 am
 
Forum: Human Biology
Topic: The Fiber Disease
Replies: 7403
Views: 5479439


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