Total -(C+G)=A+T

So either you use C+G or you use A+T results will be same, you may use A+T.

CpG islands (CG rich regions) are of interest in a biological context because of epigenetic methylation effects. Also there is a higher incidence of nucleotide transversions /transitions in CG rich regions relative to AT rich regions.

I think that Bhoj may be thinking of Chargaff's rule that C=G and A=T but the sum C+G does not usually equal A+T

@stuart stephen,@paul Rutland,@Bohj R Singh

Thanks alot