The human body is said to contain approximately 50.0 grams of DNA in the entire body. If the number of nucleotides in ONE STRAND of DNA is approximately 3.0 x 106, and the average molar mass of a nucleotide is 327 g/mol, what is the average molar mass of an entire DNA double helix?
You are off by 3 orders of magnitude. The number of base residues (not nucleotides, which are monomers) in a single polymeric strand of DNA is 109.
106 is just a million. That is nowhere close, let alone approximately, to the actual amount of DNA in a single strand of human DNA.