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A paramutation is an trans-mutational occurrence known in epigenetics to cause a heritable change on one allele as a result of another (also found between homologous sequences), normally occuring at a single loci. The allele in which a variation occurs is coined paramutant, while the allele inducing the variation is known as paramutagenic. The mechanism of this interaction is not entirely known, however it is believed to be similar in mechanism to other epigenetic interactions such as genomic imprinting. Paramutations have the ability to alter multiple phenotypes of an organism due to altered levels of gene expression. Although a paramutagenic allele may no longer be present, the offspring of an paramutated organism can still maintain the paramutated allele and thus present the altered phenotype. Paramutation has the capability to result in the maintenance of an entire array of phenotypes by one single allele of a gene. Similar allelic interactions have been discovered in other organisms such as mice and tomatoes.

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Recent experiments provide evidence for these paramutational occurences as RNA-mediated heritable chromatin alterations via RNAi pathway genes. This being said, not all paramutations can be distinguished and clarified with the mechanisms of RNAi-mediated transcriptional silencing. 



REFERENCES:

Paramutation. (2013, February 28). In Wikipedia, The Free Encyclopedia. Retrieved 14:06, September 6, 2013, from http://en.wikipedia.org/w/index.php?title=Paramutation&oldid=541306774

Mario Alberto Arteaga-Vazquez, Vicki Lynn Chandler. Paramutation in maize: RNA mediated trans - generational gene silencing. Current Opinion in Genetics and Development. 2010; 20(2): 156-163http://www.sciencedirect.com/science/article/pii/S0959437X10000213