Why did natural selection favor the use of thymine as a base in DNA instead of uracil even though uracil was presumably present in RNA, when it served as the genetic material during the early evolution of life?
A)Thymine was more stable.
B)Thymine paired better with adenine than did uracil.
C)Retention of uracil as a DNA base would make it hard to tell whether a uracil was supposed to be at a particular site or whether it resulted from damage to cytosine.
D)Thymine is resistant to all chemical treatments.
E)Retention of uracil as a DNA base would make it hard to tell whether a uracil was supposed to be at a particular site or whether it resulted from damage to guanine.

Question

Quizplus · Accepted Answer

Thymine is used in DNA instead of uracil because cytosine can deaminate to form uracil, which would lead to mutations if uracil were a normal component of DNA. Using thymine allows cells to recognize and repair such mutations.

Why Did Natural Selection Favor the Use of Thymine as a Base