Molecular Weight Calculator DNA and RNA

Molecular Weight Formula:

\[ MW = \sum(MW_{nuc}) \]

Molecular Weight (MW):

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1. What is Molecular Weight of DNA/RNA?

The molecular weight of a DNA or RNA sequence is the sum of the molecular weights of its constituent nucleotides. It's essential for various molecular biology applications including PCR, sequencing, and cloning.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ MW = \sum(MW_{nuc}) \]

Where:

\( MW \) — Molecular weight of the sequence (g/mol)
\( MW_{nuc} \) — Molecular weight of individual nucleotides

Nucleotide Weights:

DNA: A=331.2, T=322.2, C=307.2, G=347.2 g/mol
RNA: A=347.2, U=324.2, C=323.2, G=363.2 g/mol

Explanation: The calculator sums the weights of all nucleotides and subtracts 18.02 g/mol for each phosphodiester bond formed between nucleotides.

3. Importance of Molecular Weight Calculation

Details: Knowing the molecular weight is crucial for preparing solutions with specific molar concentrations, designing primers, and calculating yields in molecular biology experiments.

4. Using the Calculator

Tips: Enter the DNA or RNA sequence (case insensitive), select the molecule type (DNA or RNA). The sequence should only contain valid nucleotides (A,T,C,G for DNA; A,U,C,G for RNA).

5. Frequently Asked Questions (FAQ)

Q1: Why are DNA and RNA nucleotide weights different?
A: RNA nucleotides contain an additional hydroxyl group at the 2' position of the ribose sugar, making them slightly heavier than DNA nucleotides.

Q2: Does the calculator account for modifications?
A: No, this calculator only works with standard nucleotides. Modified bases would require adjusted molecular weights.

Q3: How accurate is this calculation?
A: It provides theoretical molecular weight based on average isotopic composition. For exact mass, isotopic distribution should be considered.

Q4: Why subtract water for each bond?
A: When nucleotides polymerize, a water molecule is lost with each phosphodiester bond formed.

Q5: Can I calculate molecular weight for both strands of DNA?
A: This calculator works for single strands. For double-stranded DNA, calculate each strand separately and sum the results.