How many restriction sites fragments per genome?


Sun Jan 14 21:47:46 EST 1996


In article <jXI+TCA7Xj9wEwFM at advbtech.demon.co.uk>, Geoff Scopes
<geoff at advbtech.demon.co.uk> wrote:
> 
> I am planning to ligate linkers to restriction digested human genomic
> DNA. In order to ensure I am adding an excess of linkers I would like to
> do a rough calculation of the number of restriction fragments that will
> be generated.
> Does anybody know of a formula to calculate the number of restriction
> fragments given the size of the genome (I was going to use 3x10+9bp) and
> the size of the restriction site (6bp in this case)?
> Or is there a simpler method to calculate the amount of linkers required
> for a given amount of DNA?
> -- 
> Geoff Scopes

Try:

# frags = G / 4^c

where G is genome size in bp's and c is the number of bases in the
recognition sequence.  Of course, 4^c is really just an estimate of the
expected distance between sites and could be incorporated with an
empirically derived value for organisms in which it is available (that is
when enzymes cut more or less frequently than expected).  Tony



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