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The retrotransposons and certain DNA-transposons, are "jumping" sequences which may be incorporated elsewhere in the genomic DNA of an organism, through varying mechanisms. This insertion is almost random in case of retrotransposons and most DNA-transposons, but some transposing enzymes show specificity in selection of insertion sites. In either case, the "copy-paste" mechanism of transposition is essentially a random process(considering the frequency and place of transposition) and therefore, the extent of transposition should vary among all individuals, and all cells of a single individual. My question is,

Is the extent of transposition random and varied among the different somatic cells of an individual or is there a regulatory mechanism which ensures that there is not much difference in the net content of DNA (caused by unequal transposition) by equalizing the extent of transposition in different individuals or different cells of the same individual? If not, does this unequal c-value in different cell cause any troubles?

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I'll have to find a reference before I can post an answer but I am pretty sure these will be independent processes in each cell. I would be fascinated to learn the opposite but I very much doubt it. –  terdon Nov 8 '13 at 4:11
    
@terdon If it isn't equalized, will not the net DNA content(amount i.e. C-value) vary among different cells, and different individuals of the species? –  Satwik Pasani Nov 10 '13 at 3:52
    
for germ cells, I know that transposition is very tightly controlled.. most of the times transposons are heterochromatinized which reduces the rate of transposition. Will look up if there is any limit for the increased DNA content (or maximum observed expansion) –  WYSIWYG Nov 10 '13 at 13:41
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Transposition may occur at any given time in life, and in any cell. There are several cases known where transposition interests somatic cells (give a look here for reference). However, the frequency of transposition events is low, and the difference in amount of DNA between different cells in an individual is low. When you reason at the level of different individuals, however, the proportion of genome affected by transposable elements may be relatively high (give a look here for a reference)

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