Structure of DNA (Basics)

  • Thread starter rwooduk
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I'm getting confused with the type of bonding (1) between the nucleotides and (2) between the nucleotide and the "sugar phosphate backbone".

This diagram:

http://tigger.uic.edu/classes/phys/phys461/phys450/ANJUM04/DNA_helix.jpg

Shows hydrogen bonds between the nucleotide bases. But then Wiki

The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. According to base pairing rules (A with T and C with G), hydrogen bonds bind the nitrogenous bases of the two separate polynucleotide strands to make double-stranded DNA.

Says they are joined by covalent bonds. Are they covalent hydrogen bonds?

Really just need to know the type of bonding (1) between the nucleotides and (2) between the nucleotide and the "sugar phosphate backbone".

If anyone can help please.
 

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  • #2
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Nucleotide: sugar & base & phosphate

Nucleoside: sugar & base

Nucleobase: base
 
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  • #3
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Nucleotide: sugar & base & phosphate

Nucleoside: sugar & base

Nucleobase: base

Ahh, think I see what you are saying, so the Nucleotide is the full thing and they are joined to each other via covalent bonds to make the backbone.

However the two backbones (nucleotide chains) need joining together, through bonding of nucleobases and that bond is a Hydrogen bond.

Does that sound right?

Thanks for the reply!
 
  • #4
Ygggdrasil
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Yes. DNA is a double helix consisting of two strands (sometimes we call one strand the Watson strand and the other the Crick strand). Each strand is a polymer of nucleotides connected via covalent bonds (phosphodiester bonds, to be precise). The Watson and Crick strands associate non-covalently through hydrogen bonding between the nucleobases.
 
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  • #5
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Yeah, they mean the joining of the nucleotides. They are covalently linked; sugar-phosphate backbone, phosophodiester, 3' and 5', that stuff.

So in DNA, every unit/nucleotide is linked to three others. The one before and the one after in the polymer-backbone(covalently), and the one it pairs up with in the other strand(hydrogen bridge interaction).

A picture that actually shows the phosphate part, the sugar part and the base part will make it clear, if it is not already.
 
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