optical density of a 400 base pair long 1ml DNA solution was found to be 0.052. How many DNA molecules are present in the solution

1 optical density is equal to 50μg/ml of dsDNA.
0.052 corresponds to 2.6μg/ml of dsDNA.
Average molecular weight of 1 nucleotide base pair is 650 dalton. So, mol. wt. of 400bp is 650x400=260000.
Number of moles of DNA is 2.6/260000=1x10​-11
One mole contain 6x1023 molecules. So, 1x10​-11 moles will contain 6x1023x1x10​-11=6x1012 DNA molecules.

  • 9
What are you looking for?