Question

Which of these promoter elements has a high propensity of developing mutation given the eukaryotic gene was inserted in prokaryotes?

(a) CCAAT box

(b) CPG islands

(c) TATA box

(d) Enhancer

The question was posed to me in an interview for job.

Origin of the question is Transcription in Eukaryotes : Activators and Repressors topic in section Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

Correct answer is (b) CPG islands

The explanation: This is because prokaryotic methylases would methylate the C bases of the CPG region. Then it there is a de-amination of C base, it will resemble a T base which is not as easily distinguishable as U by UDG. So, this region is very mutagenic.