The Skew Diagram

Let’s see if we can take advantage of these peculiar statistics caused by deamination to locate ori even more accurately than the approach that we illustrated in the figure in the Peculiar Statistics of the Forward and Reverse Half-Strands lesson. As the table from Deamination illustrates, the difference between the total amount of guanine and the total amount of cytosine is negative on the reverse half-strand ($201634 − 219518 = −17884$) and positive on the forward half-strand ($211607 − 207901 = 3706$). Thus, our idea is to traverse the genome, keeping a running total of the difference between the counts of G and C. If this difference starts increasing, then we guess that we’re on the forward half-strand; on the other hand, if this difference starts decreasing, then we guess that we’re on the reverse half-strand.

See the figure below: