Ch. 19 - Control of Gene Expression in Eukaryotes

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook

Freeman 8th Edition

Ch. 19 - Control of Gene Expression in Eukaryotes

Problem 8

Chapter 19, Problem 8

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

Verified step by step guidance

Identify the role of p53: p53 is a protein that functions as a tumor suppressor. It is involved in regulating the cell cycle, DNA repair, and apoptosis (programmed cell death).

Understand the effect of continuous active p53: If p53 is continuously active, it would constantly signal cells to either repair DNA damage or undergo apoptosis.

Predict cellular outcomes: With continuous activation, cells might enter apoptosis more frequently, even in cases where DNA damage is minimal or repairable. This could lead to increased cell death.

Consider the impact on organism health: Excessive cell death can lead to tissue damage and potentially disrupt normal tissue function, which might contribute to diseases related to premature aging or organ dysfunction.

Evaluate potential benefits: On the positive side, continuous activation of p53 could prevent the proliferation of potentially cancerous cells, thereby reducing the risk of developing tumors.

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Key Concepts

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

p53 Protein Function

The p53 protein is a crucial tumor suppressor that regulates the cell cycle and prevents the proliferation of cells with damaged DNA. It acts as a transcription factor, activating genes involved in DNA repair, cell cycle arrest, and apoptosis. Continuous production of active p53 could lead to excessive cell cycle arrest or apoptosis, preventing the survival of potentially cancerous cells.

Mutation Effects

Mutations can alter the normal function of proteins, potentially leading to uncontrolled cell growth or cell death. In the case of p53, a mutation that causes its continuous activation may disrupt the balance of cell proliferation and death, leading to an increased rate of apoptosis. This could result in tissue degeneration or impaired tissue regeneration, affecting overall organism health.

Cell Cycle Regulation

The cell cycle is a series of phases that a cell goes through to divide and replicate. It is tightly regulated by various proteins, including cyclins and cyclin-dependent kinases, as well as tumor suppressors like p53. Continuous activation of p53 would likely lead to prolonged cell cycle arrest, preventing cells from entering mitosis, which could hinder normal growth and repair processes in tissues.

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Related Practice

Textbook Question

Compare and contrast the items in each pair:

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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.

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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.

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Textbook Question

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

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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.

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