Why is thymine used in DNA rather than uracil?
A) Thymine is more hydrophobic, so it stacks better in the helix.
B) If cytosine is deaminated, it forms uracil, which can be easily distinguished from thymine.
C) Thymine is not capable of wobbling, so it pairs more accurately than uracil.
D) All of these are correct.

Question

Quizplus · Accepted Answer

The presence of thymine in DNA instead of uracil is primarily because when cytosine undergoes deamination, it converts into uracil. If uracil were normally present in DNA, the cell would not be able to distinguish between uracil that belongs there and uracil that appeared due to cytosine deamination. This could lead to errors in the DNA sequence. Thymine, on the other hand, does not arise from such a mutation, making it easier for repair mechanisms to recognize and correct errors.

Why Is Thymine Used in DNA Rather Than Uracil