Why uracil is present in RNA and not in DNA?

Answer 1

methylation protects the DNA. Beside using dT instead of dU, most organisms also use various enzymes to modify DNA after it has been synthesized. Two such enzymes, dam and dcmmethylate adenines and cytosines, respectively, along the entire DNA strand. This methylation makes the DNA unrecognizable to many Nucleases (enzymes which break down DNA and RNA), so that it cannot be easily attacked by invaders, like viruses or certain bacteria. Obviously, methylating the nucleotides before they are incorporated ensures that the entire strand of DNA is protected. Thymine also protects the DNA in another way. If you look at the components of nucleic acids, phosphates, sugars, and bases, you see that they are all very hydrophilic (water soluble). Obviously, adding a hydrophobic (water insoluble) methyl group to part of the DNA is going to change the characteristics of the molecule. The major effect is that the methyl group will be repelled by the rest of the DNA, moving it to a fixed position in the major groove of the helix. This solves an important problem with uracil - though it prefers adenine, uracil can base-pair with almost any other base, including itself, depending on how it situates itself in the helix. By tacking it down to a single conformation, the methyl group restricts uracil (thymine) to pairing only with adenine. This greatly improves the efficiency of DNA replication, by reducing the rate of mismatches, and thus mutations. To sum up: the replacement of thymine for uracil in DNA protects the DNA from attack and maintains the fidelity of DNA replication. Sunil Nagpal B.tech(h)Biotechnology 2nd year LPU-Jalandhar(punjab)(India)

Answer 2

No. Uracil is only found in RNA. Its counterpart in DNA is thymine.

Answer 3

That is the WAY that the two types of nucleic acids are distinguished, or identified from one another.

Answer 4

Yes it does.

Answer 5

Yes it does. In place of Thymine.