HardChemistryHigh School (11–12)Organic Compounds with Functional Groups › BiomoleculesNumerical

A single strand of DNA reads 5′-ATGCGTAC-3′…

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A single strand of DNA reads 5′-ATGCGTAC-3′. The molar masses of the nucleotide residues, each one a nucleotide monophosphate minus a molecule of water, are: A $313.21\ \text{g/mol}$ , C $289.18\ \text{g/mol}$ , G $329.21\ \text{g/mol}$ and T $304.20\ \text{g/mol}$ . A strand with a 5′ phosphate group and a 3′ hydroxyl group has a molar mass equal to the sum of its residues plus one water ( $18.02\ \text{g/mol}$ ). Find the molar mass of this strand, its percentage of G and C, and the molar mass of the duplex it forms with its partner strand.

Need a reminder? The key ideaShow

In double-stranded DNA, A pairs with T and G pairs with C. So $A = T$ , $G = C$ and $A + T + G + C = 100\%$ . An A-T pair has 2 hydrogen bonds and a G-C pair has 3. A strand of $n$ nucleotides has $n - 1$ phosphodiester linkages. A chain of nucleotides has a molar mass equal to the sum of the nucleotide residues plus one water.

The worked solution

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