Asked by: Cenaida Schafernicht
science genetics

Why do hydrogen bonds form between purines and pyrimidines?

Last Updated: 23rd May, 2020

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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.

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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.

Beside above, what type of bonds form between purines and pyrimidines? Purines always bond withpyrimidinesvia hydrogen bonds following the Chargaffrule in dsDNA, morespecifically each bond followsWatson-Crick base pairingrules. Therefore adenine specificallybonds to thymineforming two hydrogen bonds, whereasguanine formsthree hydrogen bonds withCytosine.

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.

Why there is double bond between adenine and thymine?

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.

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What is the difference between a purine and a pyrimidine?

The purines in DNA are adenine and guanine,thesame as in RNA. The pyrimidines in DNA arecytosineand thymine; in RNA, they are cytosine anduracil.Purines are larger than pyrimidines becausethey havea two-ring structure while pyrimidines only have asinglering.

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How many hydrogen bonds are in C and G?

Three hydrogen bonds form between guanineandcytosine. Two hydrogen bonds form between adenineandthymine or adenine and uracil.

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What does thymine pair with?

It allows something called complementarybasepairing. You see, cytosine can form three hydrogenbondswith guanine, and adenine can form two hydrogen bondswiththymine.

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What holds the nitrogen bases together in DNA?

Strands of DNA are made of the sugar andphosphateportions of the nucleotides, while the middle parts aremade of thenitrogenous bases. The nitrogenous baseson the twostrands of DNA pair up, purine with pyrimidine (Awith T, Gwith C), and are held together by weakhydrogenbonds.

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How do the 4 bases of DNA pair up?

Attached to each sugar ring is a nucleotidebase,one of the four bases Adenine (A), Guanine (G),Cytosine(C), and Thymine (T). The hydrogen bonding betweencomplementarybases holds the two strands of DNAtogether. Hydrogenbonds are not chemical bonds.

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What type of bonds connect the Deoxyribose?

In DNA and RNA, the phosphodiester bond isthelinkage between the 3' carbon atom of one sugar molecule and the5'carbon atom of another, deoxyribose in DNA and riboseinRNA. Strong covalent bonds form between the phosphategroupand two 5-carbon ring carbohydrates (pentoses) over twoesterbonds.

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What are the two purines in DNA?

There are many naturally occurring purines.Theyinclude the nucleobases adenine (2) and guanine (3). InDNA,these bases form hydrogen bonds with theircomplementarypyrimidines, thymine and cytosine,respectively.

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Where are covalent bonds found in DNA?

Covalent bonds occur within each linear strandandstrongly bond the bases, sugars, and phosphate groups(bothwithin each component and between components). Hydrogenbondsoccur between the two strands and involve a base fromone strandwith a base from the second in complementarypairing.

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How does adenine and thymine bond?

Adenine (purine) and thymine(pyrimidine)form two hydrogen bonds[ 1 using NITROGEN ATOMother usingOXYGEN ATOM. Guanine (purine) and cytosine (pyrimidine)form threehydrogen bonds [ 2 using NITROGEN ATOM and oneusing OXYGENATOM]. DNA (deoxyribonucleic acid) is the geneticmaterial of thecell.

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