שאלה | Not stated directly in the text, but among the 573 sites used as a biological clock, about ¼ of the sites increased in methylation levels with age. Why do you think methylation levels tend to increase more than to decrease with age?

Not stated directly in the text, but among the 573 sites used as a biological clock, about ¼ of the sites increased in methylation levels with age. Why do you think methylation levels tend to increase more than to decrease with age?

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		Because methylation is always required to maintain silencing while demethylation is needed mainly during reprograming in early development.
		Because older animals express fewer genes.
		Because changes in environment induce more gene repression than gene expression.
		Because methylation is a passive process and demethylation is an active process.