Molcular weight of E.coli DNA is 3.1×109g∕mol. Molecular weight of DNA = Number of base pairs × average molecular weight of nucleotide pair. Therefore, number of base pairs = molecular weight of DNA / average molecular weight of nucleotide pair =3.1×109∕660=4.70×106. One base pair contributes of 0.34nm length. Hence, 4.70×106 base pair contributes to 4.70×106×0.34=1.6×106nm=1.6mm.