2007-05-06 22:35:11 · 7 answers · asked by naveen k 1 in Science & Mathematics ➔ Biology
The answer given by mad g g is correct.
I would simply like to simplify the whole thing by saying that this is related to half life of these two classes of macromolecules(DNA and RNA). DNA being the gene it has to have a longer half life than RNA which has to function for a while. Presence of thymine in DNA confers long life.
2007-05-09 15:23:08 · answer #1 · answered by Ishan26 7 · 1⤊ 0⤋
Rna Uracil
2016-10-03 07:28:56 · answer #2 · answered by ? 4 · 0⤊ 0⤋
In RNA thymine is replaced by uracil as the base complementary to adenine. This base is also a pyrimidine and is very similar to thymine. Uracil is energetically less expensive to produce than thymine, which may account for its use in RNA.
In DNA, however, uracil is readily produced by chemical degradation of cytosine, so having thymine as the normal base makes detection and repair of such incipient mutations more efficient. Thus, uracil is appropriate for RNA, where quantity is important but lifespan is not, whereas thymine is appropriate for DNA where maintaining sequence with high fidelity is more critical.
2007-05-08 01:43:36 · answer #3 · answered by The VIP 2 · 0⤊ 0⤋
The answer to your question would be clearer if a very closely related question is answered first. "Why Uracil is substituted by Thymine in DNA?"
Thymine is nothing but 5 - Methyl Uracil.
In DNA, thymine is preferred over uracil due to the following 2 main reasons:
1) Thymine base pairs only with Adenine. Although Uracil shows higher affinity for Adenine, it can also bind to cytosine, guanine and another uracil. Chances of errors during replication is possible if uracils were to be present in DNA.
2) The methyl group in thymine protects the DNA. When cytosine in the DNA molecules are found to undergo deamination to form uracil. This can lead incorrect genetic information. Use of prevents this. The DNA repair systems detects the presence of uracil in the DNA and changes it to cytosine. If uracil were to be present the repair system will have hard time recognising which is the correct uracil which is the deaminated cytosine!!!
Essentially, preservation of genetic information in DNA is done more efficiently by thymine than uracil.
Now, to answer your question...
The need for maintaining the genetic information for a long period of time does not arise in RNA. mRNA that carries the genetic information has a very short life span. As large numbers of mRNAs are synthesized in the cells, a few mistakes can be tolerated. Therefore thymine is not needed. Uracil will do! Also, the fact that dUMP is the substrate for the production of dTMP indicates that using uracil will be more economical metabolically. You don't have to spend a few ATPs in these reactions to synthesize thymidine from uridine.
It is probably for this reason, that TMP is never produced it is deoxy TMP that is produced!!!!
2007-05-09 07:53:55 · answer #4 · answered by mad g 2 · 5⤊ 0⤋
Uracil is appropriate for RNA, where quantity is important but lifespan is not, whereas thymine is appropriate for DNA where maintaining sequence with high fidelity is more critical.
i think you got it....
2007-05-07 00:22:23 · answer #5 · answered by uma 2 · 1⤊ 2⤋
"Why" is often an impossible question in science.
It just is!
RNA contains uracil, and DNA contains thymine. It's as simple as that.
2007-05-07 00:18:24 · answer #6 · answered by solver 3 · 0⤊ 5⤋
Mad G is correct. The rest are boastful pompous asses who for some reason, need to impress you with the fact they took biology in college - when they were sober - once.
2007-05-14 12:56:33 · answer #7 · answered by michaelhobbsphd 3 · 0⤊ 2⤋
Uracil is a component of several coenzymes that act in conjunction with enzymes in several processes of carbohydrate metabolism.
2007-05-07 02:36:33 · answer #8 · answered by bharu 3 · 0⤊ 3⤋