1. Why must DNA have thymine instead of Uracil?
2. Why is it necessary for RNA to have uracil instead of thymine?

Question

1. Why must DNA have thymine instead of Uracil?
2. Why is it necessary for RNA to have uracil instead of thymine?

anonymous · Answer

thymine has a methyl group  which is not found in uracil. Having a methyl group means it is more stable. That is why thymine is more stable that uracil. 

DNA is more stable than RNA because DNA has deoxyribose sugar and RNA has ribose sugar. So DNA has thymine base and RNA has uracil. Also, all genetic info is stored in DNA, so DNA has to be stable and 'long-lived' to stored the information. When you need a protein, you need this genetic info but DNA don't move out from nucleus, so you need RNA because after you get your protein made, you don't need this info anymore and RNA is degraded.

Correct me if i'm wrong.

kayne · Answer

@Natshane you'll find a nice discussion on this topic over here: http://openstudy.com/study#/updates/4f79c24de4b0ddcbb89ee158

anonymous · Answer

isn't it because of demethylation when your DNA is mutated.and can't be recognised

anonymous · Answer

@yukitou Yes, I do remember my lecturer mentioned something about that. And that RNA needed uracil because it is synthesis and degraded frequently that's why they have uracil that is energy saving. 

@Kayne thank you! That is a great link! I do gain a lot of new information from that discussion.

@jazrio hey! Fancy seeing you here =D Well, I think that only happens when there is mutation, but you have a point. Have to look it up again.

kayne · Answer

you're welcome @Natshane