本题目来源于试卷: Continuity and Change D.5 Gene Expression，类别为 IB生物学
[单选题]
Which of the followi/tzzj cc0 r8m *+kiq-tgowfa+7s 8a ;hng statements is / are correct regswwk; qllm tex5 rf.m/t.5n6( arding the epigenetic regulation of gene expressw5.5lmtnxe/;tswl6q( k fr m.ion?
I. The base that undergoes most frequent methylation is adenine.
II. Gene transcription is inhibited by methylation of DNA
III. Methylation of histones only causes activation of transcription
A. II only
B. I and II only
C. II and III only
D. I, II and III
参考答案: A
本题详细解析:
When DNA is methylated at promoter regions, it leads to a closed chromatin structure and prevents transcription factors from binding to the promoter (Statement II). This inhibits the initiation of gene transcription and results in reduced gene expression. The most frequently methylated base in epigenetic regulation is cytosine, not adenine (Statement I). Methylation of histones does not just activate transcription (Statement III), it can both activate and repress gene transcription, depending on the specific histone residue being methylated and the context of other epigenetic modifications. Choice A is therefore the correct answer. Choices B, C and D are incorrect as they include Statements I or III or both.
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