Before revision:  The tails are heavier -- i.e. the fraction of genes and the expression levels are much higher (lower) -- in tumors than in bacteria , presumably due to epigenetic factors . Different tissue tumors show remarkably similar tails, indicating a kind of universality in cancer phenomena.
After revision:  The tails are heavier -- i.e. the fraction of genes and the expression levels vary much more -- in tumors than in bacteria , presumably due to epigenetic factors . Different tissue tumors show remarkably similar tails, indicating a kind of universality in cancer phenomena.