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Name: Don
Status: student
Grade: 9-12
Location: N/A
Date: October 2007

Question:
can you please explain why hydrogen bonds are used to hold the double helix DNA together. why would covalent bonds have a poor chance?



Replies:
Covalent bonds would do a fantastic job of holding the helix together -- too good a job, in fact. An organism is continually unzipping DNA to make proteins (RNA attaches to the unzipped DNA during a process called 'transcription'). If the DNA was held together with covalent bonds, the organism would need to use a lot more energy to break those bonds, and a lot more energy to recreate the bonds. This would be extremely inefficient, and may make errors happen more in DNA. Depending on the type of covalent bond, the shape of the DNA molecule may change or be more rigid. If DNA's shape were to change, it might work as well, but it might not work at all. Certainly the enzymes that exist now are specialized for DNA as it is -- they would not work with a differently shaped DNA molecule.

Hope this helps,

Burr



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