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Ch. 19 - Control of Gene Expression in Eukaryotes
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
All textbooksFreeman 8th EditionCh. 19 - Control of Gene Expression in EukaryotesProblem 9
Chapter 19, Problem 9

In the follow-up work to the experiment shown in Figure 19.6, the researchers used a technique that allowed them to see if two DNA sequences are in close physical proximity (association). They applied this method to examine how often an enhancer and the core promoter of the Hnf4a regulatory gene were near each other. A logical prediction is that compared with rats born to mothers fed a healthy diet, the Hnf4a gene in rats born to mothers fed a protein-poor diet would



a. Show no difference in how often the promoter and enhancer associated
b. Never show any promoter–enhancer association
c. Show a lower frequency of promoter–enhancer association
d. Show a higher frequency of promoter–enhancer association

Verified step by step guidance
1
Examine the hypothesis and null hypothesis presented in the image. The hypothesis suggests that protein-deprived mothers will produce offspring with abnormal histone modifications, while the null hypothesis suggests normal histone modifications.
Review the experimental setup. Rat mothers were provided with either a normal or low-protein diet during pregnancy and nursing. After weaning, rat pups were fed a normal diet and raised to old age. Histone modifications and transcription levels of the Hnf4a gene were measured.
Analyze the results shown in the image. The graph indicates that offspring of mothers fed a low-protein diet have higher levels of histone modifications promoting condensed chromatin and lower levels of modifications promoting decondensed chromatin compared to offspring of mothers fed a normal diet.
Consider the implications of these results. Condensed chromatin is generally associated with reduced gene expression, while decondensed chromatin is associated with increased gene expression. The lower transcription levels of the Hnf4a gene in offspring of low-protein diet mothers suggest reduced promoter-enhancer association.
Based on the analysis, predict the effect of a protein-poor diet on the promoter-enhancer association of the Hnf4a gene. Given the reduced transcription levels and increased condensed chromatin, it is logical to predict a lower frequency of promoter-enhancer association in rats born to mothers fed a protein-poor diet.

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Key Concepts

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

Epigenetics

Epigenetics refers to the study of changes in gene expression that do not involve alterations to the underlying DNA sequence. These changes can be influenced by environmental factors, such as nutrition, and can affect how genes are turned on or off. In the context of the question, the focus is on how a mother's diet may lead to epigenetic modifications in her offspring, potentially impacting their health and development.

Promoter-Enhancer Interaction

Promoter-enhancer interactions are crucial for the regulation of gene expression. Enhancers are DNA sequences that can increase the likelihood of transcription of a particular gene, while promoters are regions where the transcription machinery assembles. The physical proximity of these elements, as examined in the study, is essential for understanding how gene expression is modulated in response to different nutritional conditions.

Histone Modifications

Histone modifications are chemical changes to the proteins around which DNA is wrapped, influencing chromatin structure and gene accessibility. These modifications can lead to either a condensed state, which represses gene expression, or a decondensed state, which promotes transcription. The study investigates how a low-protein diet affects these modifications, particularly in the context of the Hnf4a gene, which is important for metabolic regulation.
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Histone Acetylation
Related Practice
Textbook Question

Imagine discovering a loss-of-function mutation in a eukaryotic gene. You determine the gene's nucleotide sequence from the start site for transcription to the termination point of transcription and find no differences from the wild-type sequence. Explain where you think the mutation might be and how the mutation might be acting.

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.

Textbook Question

Predict how a mutation that caused continuous production of active p53 would affect the cell.

Textbook Question

Imagine repeating the experiment on epigenetic inheritance that is shown in Figure 19.6. You measure the amount of radioactive uridine (U) incorporated into Hnf4a mRNA in counts per minute (cpm) to determine the level of Hnf4a gene transcription in rats born to mothers fed either a normal diet or a low-protein diet. The results are 11,478 cpm for the normal diet and 7368 cpm for the low-protein diet. For this problem, your task is to prepare a graph similar to the one at the bottom of Figure 19.6 that shows the normalized results for the low-protein diet relative to the normal diet. Normalizing values means that the value obtained from one condition is expressed as 1.0 (the norm; the normal diet in this case) and the values obtained from any other conditions (low-protein diet in this case) are expressed as decimal values relative to the norm.