How do you calculate the molecular weight of DNA?

The molecular weight of DNA can be calculated by considering the molecular weights of its constituent nucleotides (adenine, guanine, cytosine, and thymine) and the backbone of phosphate and deoxyribose.

Here are the steps to calculate the molecular weight of DNA:

Determine the base sequence: The molecular weight of DNA depends on its base sequence, which includes the four nucleotides: adenine (A), guanine (G), cytosine (C), and thymine (T).

Find the molecular weight of each nucleotide: Each nucleotide consists of a nitrogenous base (adenine, guanine, cytosine, or thymine), a deoxyribose sugar, and a phosphate group. The average molecular weights of the four nucleotides are approximately:

Adenine: around 313.2 g/mol
Guanine: around 329.2 g/mol
Cytosine: around 289.2 g/mol
Thymine: around 304.2 g/mol
Calculate the total molecular weight: Multiply the molecular weight of each nucleotide by its frequency in the DNA sequence and sum them up.

Adjust for backbone and structure: The molecular weight of the sugar-phosphate backbone must also be taken into account. When calculating the molecular weight of DNA, consider the average molecular weight of the phosphate group and deoxyribose sugar, which is approximately 180 g/mol per base pair (including linkage between bases).

Combine the results: Add up the molecular weights of the bases and the sugar-phosphate backbone for the entire DNA sequence.

For example, if you have a DNA sequence with a known number of A, G, C, and T bases, multiply each base's molecular weight by its count, and sum these up. Then, multiply the total length of the DNA sequence (number of base pairs) by the average molecular weight of the sugar-phosphate backbone. Add the two results together to get the molecular weight of the DNA sequence.