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Ch. 12 - DNA Organization in Chromosomes
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All textbooksKlug 12th EditionCh. 12 - DNA Organization in ChromosomesProblem 27

Chapter 12, Problem 27

Spermatogenesis in mammals results in sperm that have a nucleus that is 40 times smaller than an average somatic cell. Thus, the sperm haploid genome must be packaged very tightly, yet in a way that is reversible after fertilization. This sperm-specific DNA compaction is due to a nucleosome-to-nucleoprotamine transition, where the histone-based nucleosomes are removed and replaced with arginine-rich protamine proteins that facilitate a tighter packaging of DNA. In 2013 Montellier et al. showed that replacement of the H2B protein in the nucleosomes with a testis-specific variant of H2B called TSH2B is a critical step prior to the nucleosome-to-nucleoprotamine transition. Mice lacking TSH2B retain H2B and their sperm arrest late in spermatogenesis with reduced DNA compaction. Based on these findings, would you expect that TSH2B-containing nucleosomes are more or less stable than H2B-containing nucleosomes? Explain your reasoning.

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Hey everyone. Let's take a look at this question together to fit the DNA inside the nucleus. The DNA is wrapped around the his stones forming the structure called nuclear zones. What makes the D. N. A. Strongly attached to the his stones. So let's recall what we've learned about the makeup of DNA. To try to figure out why it's strongly attached to his stones. So we know that one key characteristic about DNA is that it is negatively charged. And this is due to the phosphate groups found within D. N. A. And this is important because when we're talking about its strong attachment to his stones, the reason for that being his stones are actually positively charged. And we know that when we have one thing being negative and one thing being positive we have that strong attachment between the two. And so the reason why D. N. A. Is strongly attached to the his stones is due to their charge differences or answer choice. A The correct answer because we know that D. N. Is entirely negatively charged because of its phosphate groups and his stones are positively charged. So we get this attraction between the two because of those opposite charges. And that allows D. N. A. To be strongly attached to the his stones due to their charge differences or answer choice. A. I hope you found this video to be helpful. Thank you and goodbye
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While much remains to be learned about the role of nucleosomes and chromatin structure and function, recent research indicates that in vivo chemical modification of histones is associated with changes in gene activity. One study determined that acetylation of H3 and H4 is associated with 21.1 percent and 13.8 percent increases in yeast gene activity, respectively, and that histones associated with yeast heterochromatin are hypomethylated relative to the genome average [Bernstein et al. (2000)]. Speculate on the significance of these findings in terms of nucleosome–DNA interactions and gene activity.
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An article entitled 'Nucleosome Positioning at the Replication Fork' states: 'both the 'old' randomly segregated nucleosomes as well as the 'new' assembled histone octamers rapidly position themselves (within seconds) on the newly replicated DNA strands' [Lucchini et al. (2002)]. Given this statement, how would one compare the distribution of nucleosomes and DNA in newly replicated chromatin? How could one experimentally test the distribution of nucleosomes on newly replicated chromosomes?
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