The molar concentration of DNA is the molar concentration of the total nucleotides present in one human cell. As the size of cell varies from cell to cell the whole calculation is an assumption.

Assuming the cell is of radius 0.05nm.

The volume of the perfect sphere would be 5.24 × 10^-4 or 5.24 × 10^-11 L

Total number of nucleotides:

In the nucleus: According to the Human Genome Project the 23 pairs of human chromosomes have about 3 billion base pairs that adds upto 6 billion bases = 6×10⁹ nucleotides

In the mitochondria: There are about 1500 mitochondria per cell. Each mitochondrion contains about 16000 nucleotides. Thus total mitochondrial genome per cell is 16000×1500 = 2.3×10⁷ nucleotides

Thus total DNA in a human cell is = (6 × 10⁹ + 2.3 × 10⁷) = 6 × 10⁹ nucleotides. (Mitochondrial DNA is negligible)

Therefore,

Mole = (6 × 10⁹)/(6.023 × 10²³) = 10^-14 mol (6.023 × 10²³ is the Avogadro number)

Thus,

Molarity = mole of solute/litre of solution

= 10^-14/5.24×10^-11

= 0.0002 M