Question

Which of the following statements is NOT an accurate statement about thymine dimers?:

A. Thymine dimers can cause the DNA replacement machinery to stall
B. Thymine dimers are covalent links between thymines on opposite DNA strands.
C. Prolonged exposure to sunligt causes thymine dimers to form.
D. Repair proteins recognize thymine dimers as a distortion in the DNA backbone.

Answer 1

Thymine dimers are incorrectly described as forming between strands; they form between two adjacent thymines on the same DNA strand due to UV light and can cause replication issues, but they are normally repaired by nucleotide excision.

Step-by-step explanation:

The statement that thymine dimers form between thymines on opposite DNA strands is not accurate. In reality, thymine dimers are covalent links between two adjacent thymine molecules on the same DNA strand. These structures can result from excessive exposure to ultraviolet (UV) light and are a form of DNA damage that can stall DNA replication and transcription machinery. Normally, these dimers are recognized by repair proteins that identify the distortion in the DNA double helix and correct it through a process called nucleotide excision repair, where the affected DNA is removed and replaced with the correct nucleotides.