In the course of 525 million years of vertebrate evolution, the opsin gene has gone from 5 opsins in lampreys to 4 opsins in fish, reptiles, and birds to 2 opsins in non-primate mammals and finally to 3 opsins in primates. Does the high frequency of the opsin gene’s deletion and duplication during vertebrate evolution indicate that the opsin gene is a transposon? Discuss other incidents where the duplication and/or modification genes contributed to an organism’s success.
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"A transposon, also called a transposable genetic element, is a piece of DNA that can move from one location to another in a cell's genome. Unlike an episome or prophage, transposons never exist independently. Instead, transposon movement (transposition) occurs as a type of recombination between the transposon and another DNA site - a target site - that comes in contact with the transposon," (Campbell 345). Transposons are known to jump from a genomic location to another one while other transposons have been known to copy and insert themselves elsewhere. The elements that identify an opsin for being duplicated and deleted so frequently does make it seem that it is a transposable element. Other incidents where a duplication and/or modification genes contributed to an organism's success includes that of the sickle-cell disease. Sickle-cell disease increases resistance to malaria where evolution of the sickle cell gene had taken place. Even further "evidence of the link is that the sickle cell mutation, which is caused by a single change in the sixth triplet of the gene (from GAG to GTG)," (Carroll 177) seems to be found in East Africans where malaria harbors. Thus, the frequency of the opsin gene's deltion and duplication during evolution does indicate it may be a transposable element and sickle-cell disease, through the biological theme of evolution, has caused the human species (Homo sapiens) to survive through diseases such as malaria through natural selection.
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