AAMC FL Practice Exam

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Study for the AAMC FL Exam. Prepare with comprehensive flashcards and multiple-choice questions, each equipped with hints and explanations. Gear up for your medical school entrance exam!

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What is the effect of acetylation on histones?

  1. Increases DNA binding

  2. Decreases histone attraction to DNA

  3. Promotes apoptosis

  4. Inhibits transcription

The correct answer is: Decreases histone attraction to DNA

The correct choice regarding the effect of acetylation on histones is that it decreases histone attraction to DNA. This modification typically occurs at specific lysine residues on histone proteins. When histones are acetylated, the positively charged lysine residues lose their positive charge due to the addition of the acetyl group. This reduction in positive charge weakens the interaction between the histones and the negatively charged DNA. As a result, the DNA becomes less tightly bound, facilitating a more open chromatin structure that is accessible for transcription and other nuclear processes. The broader context of this mechanism is that acetylation is associated with transcriptional activation. When histones are acetylated, it generally promotes gene expression by allowing transcription machinery greater access to the DNA.

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