Which of the Following is NOT True of a Pyrimidine

Question

Which of the following is NOT true of a pyrimidine dimer?
A) It can be repaired by photoreactivation.
B) The pyrimidines are base-paired one to another.
C) It is produced by ultraviolet light.
D) It blocks DNA replication.
E) It blocks transcription.

Accepted Answer

A pyrimidine dimer occurs when two adjacent pyrimidine nucleotides on the same strand of DNA form covalent bonds with each other, causing a kink in the DNA strand. Therefore, the pyrimidines are not base-paired one to another, making choice B incorrect. Pyrimidine dimers are produced by ultraviolet light, can block DNA replication and transcription, and can be repaired by photoreactivation.