Why is DNA a double helix?
Wouldn't it be easier if it was just a single strand, like RNA? Transcription and replication would be much easier.
Is there a purpose for the base pairings? Why does a strand such as ATTGAGGTCA need a complementary strand TAACTCCAGT? Couldn't a single strand still code for proteins perfectly fine?
Comments
The DNA molecule is a long term molecule which has to be highly conserved in order to be able to continue to provide the code for protein synthesis. Its double strand offers some protection against mutations, and allows mRNA to copy information off both strands simultaneously, increasing the efficiency of the event. mRNA is used to copy the DNA code and transport it to the cytoplasm, where it interacts with other RNA molecules to produce a protein product. When the protein has been made the mRNA is no longer used - it is a short term molecule. The strand needs to be able to pass through the rRNA and allow tRNA to add complementary bases to form the protein product. Mutations in the single stranded mRNA are not too catastrophic for the cells, as the molecule does not last for a great length of time, and further copies of the DNA can be made that are not mutated in order to create the appropriate protein product.
Sorry for this long text block
Cheers,
Another thing that being double stranded does is allow for error checking and correction.
Certain enzymes can detect mismatched bases, where the base in one strand is not complementary to the base in the other strand. This information allows the cell to take action and remedy the mismatch. If DNA were single stranded, this information would not be available.
http://www.youtube.com/watch?v=HYS6EKnQcv0
A genetic material has to be some kind of permanent in nature as it has to pass from one generation to another. Single-strandedness will render it vulnerable to enzymatic attack.