Question

Why does DNA contain Thymine but RNA contains Uracil?

Answer 1

It's thought that RNA predates DNA as a hereditary material; following those lines, uracil is a simpler molecule to synthesize than thymine and is thus more likely evolve first along with RNA. However, DNA uses thymine because it is more stable than uracil. Cytosine mutates readily into uracil, but by having thymine, it's easier to find the errors and have them corrected.

Answer 2

Saw this :)

Answer 3

Welcome to Open Study ^_^