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Asked by: Cenaida Schafernicht
science geneticsWhy do hydrogen bonds form between purines and pyrimidines?
The purines on one strand of DNA formhydrogenbonds with the corresponding pyrimidines on theoppositestrand of DNA, and vice versa, to hold the two strandstogether.Within DNA molecules, this is their most importantfunction and isknown as base pairing.
Similarly, why does a pyrimidine only bond with a purine?
The molecular structure of both pyrimidinesandpurines allow them to only be able tobondwith each other and not within the group.Thymine(pyrimidine)and adenine (purine) both have twoatomsthat can either provide a H bond or receive it.Cytosine(pyr.) and guanine (pur.) can stablish threeHbonds.
Consequently, why do purines bond with pyrimidines in DNA?
Purines (adenine and guanine) have twocarbonnitrogen ring bases. I think purines bond withpyrimidinesin the DNA ladder because adenine moleculesonly pairthymine molecules and guanine molecules only pair withcytosinemolecules. A and T bond with 2 hydrogen bonds, C andGbond with 3 hydrogen bonds.
In the DNA helix, the bases: adenine,cytosine,thymine and guanine are each linked withtheircomplementary base by hydrogen bonding.Adenine pairswith thymine with 2 hydrogenbonds. This differencein strength is because of thedifference in the number of hydrogenbonds.