True/False: The post-translational modifications of histone proteins have functi

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True/False: The post-translational modifications of histone proteins have functional roles in gene expression.
21.11: Some viruses, such as SV40, contain closed circular DNAs carrying nucleosomes. If the SV40 viral chromosome is treated with topoisomerase, and the histone is then removed, it is still supercoiled. If histones are removed before topoisomerase treatment, however, the DNA is relaxed. Explain. (Answer choices below)
21.12:

Explain these features in terms of the special requirements for histone synthesis.

Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

Problem 21.11 Some viruses, such as SV40, contain closed circular DNAs carrying nucleosomes. If the SV40 viral chromosome is treated with topoisomerase, and the histone is then removed it is still supercoiled. lfhistones are removed before topoisomerase treatment, however, the DNA is relaxed. Part A Explain Topoisomerase tums whole sections of DNA-linkers and nucleosomes. With the removal of histones windings that was hidden under compactization are revealed and mimic the original twists. The DNA makes superhelical turns about each nucleosome. These turns are constrained by binding to histone octamers and cannot be unwound by topoisomerase action. Recognition and activity sites of topoisomerases are hidden by the binding of DNA nucleosomes. With the DNA release of the histones this sequences open and relax occurs. Gaps produced by topoisomerase cannot move on DNA molecule, stopping in places of binding with nucleosomes, and are ligated at that position thereby not remove the supercoiling Submit My Answers Give U

Explanation / Answer

10. True

Histone acetylation = Activation of gene expression

Histone methylation = repression of gene expression

11. Option B is correct.

The DNA makes superhelical turns about each nucleosome. These turns are constrained by binding to histone octamers and cannot be unwound by topoisomerase action.

12.

i. S-Phase

ii. Nucleosome

iii. Transcription

iv. Introns

v. Processing

vi. Cytoplasm

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