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Ch. 19 - Epigenetics
All textbooksKlug 12th EditionCh. 19 - EpigeneticsProblem 22
Chapter 18, Problem 22

From the data in Table 19.3, draw up a list of histone H3 modifications associated with gene activation. Then draw up a list of H3 modifications associated with repression.

Are there any overlaps on the lists?

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1
span>Step 1: Understand the role of histone modifications in gene expression. Histone modifications can either activate or repress gene expression by altering chromatin structure and accessibility.</span
span>Step 2: Identify the specific histone H3 modifications that are known to be associated with gene activation. Common modifications include acetylation (e.g., H3K9ac, H3K14ac) and methylation (e.g., H3K4me3).</span
span>Step 3: Identify the specific histone H3 modifications that are known to be associated with gene repression. Common modifications include methylation (e.g., H3K9me3, H3K27me3) and deacetylation.</span
span>Step 4: Compare the lists of modifications associated with activation and repression to identify any overlaps. Consider whether any modifications can have dual roles depending on context or additional factors.</span
span>Step 5: Reflect on the biological significance of any overlaps or dual roles in histone modifications, considering how they might contribute to the dynamic regulation of gene expression.</span

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Histone Modifications

Histone modifications refer to the chemical changes made to the histone proteins around which DNA is wrapped. These modifications, such as methylation and acetylation, can influence gene expression by altering the accessibility of the DNA to transcription machinery. Understanding these modifications is crucial for analyzing their roles in gene activation and repression.
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Gene Activation and Repression

Gene activation involves the processes that increase the expression of a gene, often facilitated by specific histone modifications that promote a more open chromatin structure. Conversely, gene repression refers to mechanisms that decrease gene expression, typically associated with histone modifications that lead to a more compact chromatin configuration. Recognizing these processes is essential for interpreting the data in the context of histone modifications.
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Overlap in Histone Modifications

The overlap in histone modifications refers to the phenomenon where certain modifications can be associated with both gene activation and repression, depending on the context. This dual role can complicate the interpretation of histone modification patterns, as the same modification may have different effects based on the specific genes or cellular conditions involved. Identifying these overlaps is key to understanding the regulatory complexity of gene expression.
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Related Practice
Textbook Question

Prader–Willi syndrome (PWS) is a genetic disorder with a clinical profile of obesity, intellectual disability, and short stature. It can be caused in several ways. Most common is a deletion on the paternal copy of chromosome 15, but it can also be caused by an epigenetic imprinting disorder, and uniparental disomy, an event in which the affected child receives two copies of the maternal chromosome 15. A child with PWS comes to your clinic for a diagnosis of the molecular basis for this condition. The gel below shows the results of testing with short tandem repeats (STRs) from the region of chromosome 15 associated with the disorder.

Is this case caused by a deletion in the paternal copy of chromosome 15? Explain.


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Textbook Question

Prader–Willi syndrome (PWS) is a genetic disorder with a clinical profile of obesity, intellectual disability, and short stature. It can be caused in several ways. Most common is a deletion on the paternal copy of chromosome 15, but it can also be caused by an epigenetic imprinting disorder, and uniparental disomy, an event in which the affected child receives two copies of the maternal chromosome 15. A child with PWS comes to your clinic for a diagnosis of the molecular basis for this condition. The gel below shows the results of testing with short tandem repeats (STRs) from the region of chromosome 15 associated with the disorder.

Based on your interpretation of the data, what is the cause of PWS in this case? Explain your reasoning. 

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Textbook Question

Because the degree of DNA methylation appears to be a relatively reliable genetic marker for some forms of cancer, researchers have explored the possibility of altering DNA methylation as a form of cancer therapy. Initial studies indicate that while hypomethylation suppresses the formation of some tumors, other tumors thrive. Why would one expect different cancers to respond differently to either hypomethylation or hypermethylation therapies?

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Textbook Question

From the data in Table 19.3, draw up a list of histone H3 modifications associated with gene activation. Then draw up a list of H3 modifications associated with repression.

Are these overlaps explained by different modifications?

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Textbook Question

From the data in Table 19.3, draw up a list of histone H3 modifications associated with gene activation. Then draw up a list of H3 modifications associated with repression.

If not, how can you reconcile these differences?

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Textbook Question

Amino acids are classified as positively charged, negatively charged, or electrically neutral.

Which category includes lysine?

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