One of the key ways in which new genes appear is following a type of mutation known as a 'gene duplication'. During cell duplication, sections of DNA are often copied by accident onto the same or a different chromosome. If a segment of DNA contains an intact *gene*, then you end up with a second copy of the same gene. Sometimes this is lethal, as it results in the overproduction of some protein, or production of some protein or structure at the wrong time during development. But often these duplicated genes have no effect at all, as the production of the protein or structure they produce, is controlled by some regulator (like another protein, such as a hormone).
<span>In short, a duplicated gene can be lethal, but it may have no immediate effect at all. It is neither harmful nor beneficial, and can persist in the population for generations. </span>
<span>Once a duplicate copy of a gene gets produced this way, then *any* other kind of mutation (a substutition, inversion, frameshift error, etc.) can alter one of the two copies, and alter the resulting protein. The result is a *new gene*. </span>
<span>Note that this second mutation may occur *at the same time* as the gene duplication (i.e. a duplication where an error occurs during the creation of the second copy) ... or this second mutation may occur hundreds or thousands of generations later. </span>
<span>The end result is the same. A new gene that produces a new protein with different properties. </span>
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<span>Example: </span>
<span>The gene that codes for the production of the third pigment (protein) in the retina of humans, apes, and the monkeys of Africa and Asia that gives them all three-color vision, has been traced to a gene duplication of the second of these proteins. (Other mammals, including the monkeys of Central and South America, do not have this gene, which is why they have two-color vision ... commonly called 'color-blind.') </span>
<span>"The evolution of trichromatic color vision by opsin gene duplication in New World and Old World primates." </span> http://www.ncbi.nlm.nih.gov/pubmed/10413...
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<span>Other examples: </span>
<span>"The birth of new genes by RNA- and DNA-mediated duplication during mammalian evolution." </span> http://www.ncbi.nlm.nih.gov/pubmed/19803...
<span>"Further examples of evolution by gene duplication revealed through DNA sequence comparisons." </span> http://www.ncbi.nlm.nih.gov/pubmed/78961...
<span>"Molecular evidence that the H-2D and H-2L genes arose by duplication." </span> <span>http://www.ncbi.nlm.nih.gov/pubmed/2351932
i tried to put all evidence and details! </span><span> </span>
The first thing that the nurse should do is TO START CHEST COMPRESSION. Cardiopulmonary arrest refers to a sudden loss of blood flow, which occur as a result of the failure of the heart to actively pump blood. Performing chest compress on a victim of cardiopulmonary attack will help to restore the pumping function of the heart again.
Answer: Directional selection occurs when individuals with traits on one side of the mean in their population survive better or reproduce more than those on the other. ... Directional selection does the “heavy lifting” of evolution by tending to move the trait mean toward the optimum for the environment.
