  In this work we investigate the interplay between coherent and incoherent
charge transport in cytosine-guanine (GC) rich DNA molecules. Our objective is
to introduce physically grounded approach to dephasing in large molecules and
to understand the length dependent charge transport characteristics and
especially the crossover from coherent tunneling to incoherent hopping regime
at different temperatures. Therefore, we apply the vibronic dephasing model and
compare the results to the B\"uttiker probe model which is commonly used to
describe decoherence effects in charge transport. Using the full ladder model
and simplified 1D model of DNA, we consider molecular junctions with
alternating and stacked GC sequences and compare our results to recent
experimental measurements.
