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DNA questions

Can someone explain to me how the double helix is formed in DNA and the why it's important to DNA please -.-
Reply 1
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Mockery
17
The most important simplistic description of why DNA forms the double helices shape that it does is due to the hydrophobic effect. The DNA backbone, comprising of phosphates and ribose sugars, is hydrophilic and therefore content with being on the outskirts of the molecule subjected to the watery environment in which they are found. The nucleotide bases however are strictly hydrophobic and therefore are compelled to aggregate together and reduce the amount of space there is for water to be. As a result the bases are found in the centre of the molecule and double strands are more favourable.

The spiral or helices occurs due to the same reason. The bonding between the phosphates and ribose sugars will arrange themselves in a state which requires the least amount of energy to remain stable, therefore the more they are fighting to keep the hydrophobic bases in contact with water molecules, the more energy is needed to maintain that state. A bond angle of 180 degrees leaves huge gaps in between nucleotide base pairs in which the bases will come into contact with water (see figure 1 beautifully drawn using paint).


Figure 1


The best shape that allows the bonding between the phosphates and the ribose sugars to be at the least possible energy state is with the base pairs as close together as possible. Due to the fact that the bonding length/distance can't be 'squashed', staggering the ladder shape created by 180 degree bond angles into a shape more reminiscent of a set of stairs and then adding a twist or helices compacts the nucleotide bases as much as possible.
(edited 10 years ago)
Original post by kkboyk
Can someone explain to me how the double helix is formed in DNA and the why it's important to DNA please -.-


The DNA consists of phosphate groups, deoxyribose (a sugar molecule which is formed by five carbon atoms) and nucleobases by the names of guanine, cytosine, adenine and thymine.

The DNA double helix is formed by alternating phosphate groups and deoxyribose. Inside the DNA double helix guanine is linked with cytosine, while adenine is linked with thymine.

This DNA double helix contains the genetic information. If this genetic information is ruined by wrong linking nucleobases, it may cause genetic diseases.
(edited 10 years ago)
Reply 3
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kkboyk
OP
21
So it's due to the polarity if the phosphate group if one nucleotide and the deoxyribose of another nucleotide?
Original post by kkboyk
So it's due to the polarity if the phosphate group if one nucleotide and the deoxyribose of another nucleotide?


Nucleobases are linked by hydrogen bonds with each other, nucleobases and deoxyribose are linked by a nitrogen atom of a nucleobase and a carbon atom of deoxyribose and phosphate groups and deoxyribose are linked by an oxygen atom of a single phosphate and a carbon atom of the deoxyribose.

The hydrogen bonds consists of polarities, but I'm not entirely sure if this applies to the other compounds too.
(edited 10 years ago)

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