Textbook Question
What is chromatin?a. the histone-containing protein core of the nucleosomeb. the 30-nm fiberc. the complex of DNA and proteins found in the nucleusd. the histone and non-histone proteins in eukaryotic nuclei
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3. Energy & Cell Processes
Organization of DNA in the Cell
0:35 minutesProblem 7
Textbook Question
The following statements are about the control of chromatin condensation. Select True or False for each.T/F Reducing histone acetylase activity is likely to decrease gene transcription.T/F Mutations that reduce the number of positively charged amino acids on histones should promote open chromatin.T/F Chromatin remodeling complexes add chemical groups to histones.T/F Adding an inhibitor of DNA methylation is likely to reduce gene transcription.
Verified step by step guidance1
Identify the role of histone acetylase in chromatin structure: Histone acetylase adds acetyl groups to histones, which reduces the positive charge on histones, leading to a less compact chromatin structure and promoting gene transcription.
Analyze the effect of reducing histone acetylase activity: By reducing the activity of histone acetylase, fewer acetyl groups are added to histones, which maintains the positive charge, leading to tighter chromatin packing and potentially decreasing gene transcription.
Understand the impact of amino acid charge on histone interaction: Histones are positively charged due to the presence of amino acids like lysine and arginine. Reducing the number of these positively charged amino acids would decrease the electrostatic interaction between histones and the negatively charged DNA, potentially leading to a more open chromatin structure.
Examine the function of chromatin remodeling complexes: Chromatin remodeling complexes primarily function to change the position of nucleosomes on DNA rather than adding chemical groups to histones. They use energy from ATP hydrolysis to slide nucleosomes along the DNA, thereby altering the accessibility of the DNA for transcription.
Evaluate the role of DNA methylation in gene transcription: DNA methylation typically acts to repress gene transcription by adding methyl groups to cytosine bases in DNA, leading to a more closed chromatin configuration. Using an inhibitor of DNA methylation would prevent this methylation, likely resulting in a more open chromatin structure and potentially increasing gene transcription.
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35sKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Histone Acetylation
Histone acetylation is a post-translational modification where acetyl groups are added to the lysine residues of histone proteins. This modification reduces the positive charge on histones, leading to a more relaxed chromatin structure, which facilitates gene transcription. Conversely, reducing histone acetylase activity typically results in increased histone compaction and decreased gene expression.
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Chromatin Structure and Charge
Histones are rich in positively charged amino acids, which interact with the negatively charged DNA backbone. Mutations that reduce these positively charged residues can lead to a less compact chromatin structure, promoting an open configuration that is more accessible for transcription factors and RNA polymerase, thereby enhancing gene expression.
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Chromatin Remodeling Complexes
Chromatin remodeling complexes are multi-protein assemblies that alter the structure of chromatin, making it more or less accessible for transcription. They do not add chemical groups to histones; instead, they reposition or evict nucleosomes, allowing transcription machinery to access DNA. Their activity is crucial for regulating gene expression in response to various cellular signals.
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