Question

whats the advantage of storing information as DNA but using it as RNA ?

Answer 1

RNA is unstable while DNA is more stable. This is because RNA has ribose sugar and DNA has deoxyribose sugar. The deoxyribose sugar lacks a 2’ OH that is present in ribose sugar. The lack of this OH group makes DNA less prone to hydrolysis. Thus, free –OH in RNA can be easily oxidized making it unstable. RNA also has larger groves as compared to DNA which makes it. RNA is susceptible to alkaline degradation.

Deamination of cytosine can occur in DNA resulting in formation of uracil. Thus, the cell can determine whether there is cytosine deamination forming uracil. Hence, DNA repair enzymes can then repair this uracil deamination mutation. However, RNA also has uracil instead of thymine. Hence, if there is a deamination of cytosine in RNA, the cell cannot distinguish whether this uracil was naturally present or deaminated from cytosine. Thus, such mutations cannot be repaired by repair enzymes in RNA.

RNA is single stranded while DNA has a double stranded helical structure. If there is any mismatch in DNA, it can be easily detected due to base pairing rules. This is not possible in RNA due to its single stranded helix structure. The nucleobases in DNA are also protected as they are present in interior of the helix. Conversely, in RNA, the nucleobases are exposed to the external environment, making then susceptible for degradation. DNA is this able to store information more accurately and transfer it to next generation due to its stability. There is more accuracy for replication in DNA as mutation in one strand is easily detected by DNA repair enzymes. DNA is also less prone to mutation than RNA.

It is easier to transcribe RNA than DNA. DNA is complexed with histone proteins, making it inaccessible for transcription factors, unless these histones are removed. Further, DNA undergoes methylation to silence genes. RNA is not methylated and thus RNA polymerase and other transcription factors bind to it. mRNA also can be easily degraded. This will help in rapid turnover of mRNA which can regulate gene expression based on the needs of the cell. The Wobble hypothesis also accounts for the ability of mRNA to bind to tRNA coding for different amino acids. RNA also undergoes splicing to remove introns. This accounts for presence of introns. DNA cannot undergo alternative splicing mechanism. Thus, it is easy for DNA to store information due to its stability and easier for RNA to be used for transcription to produce proteins.