Question

Identify the disadvantages of RNA over DNA as a genetic material and explain it.

Answer 1

Hint: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) are the most important biomolecules in cell biology. The central dogma of biology states that the genetic information is present in the DNA which is transferred to mRNA and then finally expressed as proteins.

Complete answer:
DNA and RNA are both present as genetic materials in organisms. But over the course of evolution, DNA is the best choice among the two. There are a number of reasons for this. They are:
Stability:
DNA and RNA both contain ribose sugar. As the name suggests, deoxyribonucleic acid (DNA) is lacking one oxygen containing hydroxyl group. The extra oxygen atom in RNA makes it less stable when compared to DNA.
Reactivity:
Due to the same reason as above, RNA is a very reactive molecule. A genetic material should not be very reactive and should remain stable. RNA undergoes hydrolysis almost times faster than DNA.
DNA gets repaired faster than RNA due to the presence of cytosine only. Whereas in RNA, the cytosine is replaced by uracil due to a process called deamination and there can be cytosine or uracil in the position and cytosine deamination cannot be repaired in RNA unlike DNA.
Since DNA is double stranded the genetic information is protected very well than RNA. In RNA the bases are exposed and again can undergo chemical reaction very quickly.
Evolution:
A genetic material should undergo slow and gradual change to undergo evolution of a species. DNA has the capacity to undergo changes at a slower rate and RNA mutate at a very faster rate. Rapid mutations are unfavourable in most of the cases.

Note:
Even though RNA is not the first choice of organisms as genetic material it is vital in many processes including the expression of characters where the information stored in DNA has to be transcribed into mRNA and then expressed as proteins.
RNA has three main types namely – mRNA, rRNA and tRNA. The function of mRNA is already discussed above. t-RNA is useful at the time of protein synthesis to carry the right amino acids to the ribosome. One function of r-RNA is to catalyse the peptide bond formation between amino acids during protein synthesis. Some organisms that need to change really quickly and stay ahead of the immune system of the hosts have RNA as genetic materials. The best examples are viruses such as HIV and influenza.