Question 1

What are four things that influence the stability of eukaryotic mRNAs?

Accepted Answer

The stability of eukaryotic messenger RNAs (mRNAs) is influenced by several factors that can affect their degradation rates and, consequently, the level of gene expression. Four key factors that influence the stability of eukaryotic mRNAs are:

1. **5' Cap Structure**: The 5' end of eukaryotic mRNAs is modified with a 7-methylguanosine cap, which is essential for mRNA stability. This cap structure protects the mRNA from exonucleases that degrade RNA from the 5' end. It also plays a role in the initiation of translation and the export of mRNA from the nucleus to the cytoplasm.

2. **3' Poly(A) Tail**: The 3' end of eukaryotic mRNAs typically has a polyadenylate (poly(A)) tail, which is a string of adenine nucleotides. The length of the poly(A) tail influences mRNA stability, with longer tails generally conferring greater stability. The poly(A) tail also interacts with poly(A)-binding proteins (PABPs) that protect the mRNA from degradation and assist in the regulation of translation.

3. **mRNA Sequence Elements**: Specific sequence elements within the mRNA itself can influence its stability. These include AU-rich elements (AREs) and GU-rich elements, which are often found in the 3' untranslated region (UTR) of the mRNA. These elements can be recognized by specific RNA-binding proteins that either destabilize or stabilize the mRNA. For example, AREs are known to target mRNAs for rapid degradation.

4. **RNA-Binding Proteins**: The interaction of mRNAs with RNA-binding proteins (RBPs) can significantly affect their stability. RBPs can bind to specific sequences or structures in the mRNA and either protect it from degradation or target it for rapid turnover. Some RBPs stabilize mRNAs by competing with or blocking the access of decay enzymes, while others recruit components of the degradation machinery to the mRNA.

These factors work in concert to finely tune the half-life of each mRNA, thereby controlling the levels of protein synthesis within the cell. The balance between mRNA synthesis and degradation is crucial for proper cellular function and response to environmental changes.

Question 2

Which of the following eukaryotic gene regulatory mechanisms acts after transcription has been initiated?

Accepted Answer

A)  changes in chromatin structure 
B)  changes in transcriptional regulator proteins 
C)  assembly of the basal transcription apparatus 
D)  factors that increase RNA polymerase stalling 
E)  association of transcriptional coactivators 
A)  changes in chromatin structure 
B)  changes in transcriptional regulator proteins 
C)  assembly of the basal transcription apparatus 
D)  factors that increase RNA polymerase stalling 
E)  association of transcriptional coactivators D

Question 3

What type of cellular activity is known to occur within P bodies?

Accepted Answer

A)  active transcription 
B)  active translation 
C)  RNA degradation 
D)  transcriptional stalling 
E)  DNA hypermethylation 
A)  active transcription 
B)  active translation 
C)  RNA degradation 
D)  transcriptional stalling 
E)  DNA hypermethylation C

Question 4

What are three ways in which gene regulation is accomplished by modifying the structure of chromatin?

Accepted Answer

Gene regulation through the modification

Question 5

Which of the following mechanisms does NOT involve siRNA- and miRNA-based gene regulation?

Accepted Answer

A)  cleavage of mRNA 
B)  inhibition of translation 
C)  posttranslational modification 
D)  degradation of mRNA 
E)  transcriptional silencing 
A)  cleavage of mRNA 
B)  inhibition of translation 
C)  posttranslational modification 
D)  degradation of mRNA 
E)  transcriptional silencing

Question 6

Consider the regulation of galactose metabolism through GAL4. Which of the following would result from a mutation that allowed GAL3 to bind to GAL80 in the absence of galactose?

Accepted Answer

A)  Transcription of the genes involved in galactose metabolism would occur both in the presence and in the absence of galactose. 
B)  GAL80 would be able to bind to GAL4, and transcription of the genes involved in galactose metabolism would be repressed. 
C)  GAL4 would no longer be able to bind to the DNA; thus, transcription of the genes involved in galactose metabolism would occur. 
D)  GAL80 would no longer be able to stimulate transcription of the genes involved in galactose metabolism. 
E)  There would be no change in the regulation of galactose metabolism because GAL3 normally binds to GAL80 to cause a conformation change in GAL80. 
A)  Transcription of the genes involved in galactose metabolism would occur both in the presence and in the absence of galactose. 
B)  GAL80 would be able to bind to GAL4, and transcription of the genes involved in galactose metabolism would be repressed. 
C)  GAL4 would no longer be able to bind to the DNA; thus, transcription of the genes involved in galactose metabolism would occur. 
D)  GAL80 would no longer be able to stimulate transcription of the genes involved in galactose metabolism. 
E)  There would be no change in the regulation of galactose metabolism because GAL3 normally binds to GAL80 to cause a conformation change in GAL80.

Question 7

Although operons are not common in eukaryotes, eukaryotic genes may be activated by the same stimulus. Which of the following DNA regulatory sequences makes this coordinated gene expression possible?

Accepted Answer

A)  core promoter 
B)  enhancer element 
C)  response element 
D)  boundary element 
E)  silencer element 
A)  core promoter 
B)  enhancer element 
C)  response element 
D)  boundary element 
E)  silencer element

Question 8

Alternative splicing is known to be important in the regulation of the:

Accepted Answer

A)  production of heat-shock elements. 
B)  mammalian SV40 virus. 
C)  lac operon in E. coli. 
D)  metallothionein gene. 
E)  None of the answers is correct. 
A)  production of heat-shock elements. 
B)  mammalian SV40 virus. 
C)  lac operon in E. coli. 
D)  metallothionein gene. 
E)  None of the answers is correct.

Question 9

In which part of the mRNA does degradation generally begin?

Accepted Answer

A)  at the 5' end with the removal of the poly(
A)  tail 
B)  at the 5' end with the removal of the methyl cap 
C)  at the 3' end with the removal of the poly(
A)  tail 
D)  at the 3' end with the removal of the methyl cap 
E)  Removal from either end is equally likely. 
A)  at the 5' end with the removal of the poly(
A)  tail 
B)  at the 5' end with the removal of the methyl cap 
C)  at the 3' end with the removal of the poly(
A)  tail 
D)  at the 3' end with the removal of the methyl cap 
E)  Removal from either end is equally likely.

Question 10

Suppose a scientist discovered a mutant strain of C. elegans worms that had lost the ability to regulate gene expression via RNA interference mechanisms. Which of the following might she predict is a possible source of this defect?

Accepted Answer

A)  There is a mutation in the gene that encodes the Dicer enzyme that makes it nonfunctional. 
B)  There is a mutation that results in an overexpression of siRNAs. 
C)  There is a mutation in the gene that encodes the Slicer enzyme that allows it to cut RNA more efficiently. 
D)  There is a mutation in a gene that encodes an acetylase enzyme that prevents histone acetylation. 
E)  There is a mutation in a gene that encodes an enzyme that selects the correct splice site for alternative splicing. 
A)  There is a mutation in the gene that encodes the Dicer enzyme that makes it nonfunctional. 
B)  There is a mutation that results in an overexpression of siRNAs. 
C)  There is a mutation in the gene that encodes the Slicer enzyme that allows it to cut RNA more efficiently. 
D)  There is a mutation in a gene that encodes an acetylase enzyme that prevents histone acetylation. 
E)  There is a mutation in a gene that encodes an enzyme that selects the correct splice site for alternative splicing.

Question 11

Which of the following sequences or molecules is LEAST relevant to the assembly of the basal transcription apparatus for transcription?

Accepted Answer

A)  core promoter 
B)  general transcription factors 
C)  TATA box 
D)  RNA polymerase 
E)  enhancer 
A)  core promoter 
B)  general transcription factors 
C)  TATA box 
D)  RNA polymerase 
E)  enhancer

Question 12

RITS consists of:

Accepted Answer

A)  siRNAs and proteins. 
B)  miRNAs and proteins. 
C)  RISCs and mRNAs. 
D)  methyl groups and histone proteins. 
E)  DNA, histone proteins, and mRNAs. 
A)  siRNAs and proteins. 
B)  miRNAs and proteins. 
C)  RISCs and mRNAs. 
D)  methyl groups and histone proteins. 
E)  DNA, histone proteins, and mRNAs.

Question 13

Which of the following facts about eukaryotic gene regulation is TRUE?

Accepted Answer

A)  Transcriptional activator proteins bind to the DNA in a nonspecific manner. 
B)  Eukaryotic enhancers are a part of the basal transcription apparatus. 
C)  The eukaryotic regulatory promoters are highly conserved with the same consensus sequences throughout the genome. 
D)  Mediators are protein complexes involved in regulating transcription rates. 
E)  The transcriptional repressors always bind to the insulator elements. 
A)  Transcriptional activator proteins bind to the DNA in a nonspecific manner. 
B)  Eukaryotic enhancers are a part of the basal transcription apparatus. 
C)  The eukaryotic regulatory promoters are highly conserved with the same consensus sequences throughout the genome. 
D)  Mediators are protein complexes involved in regulating transcription rates. 
E)  The transcriptional repressors always bind to the insulator elements.

Question 14

siRNAs and miRNAs are produced by the:

Accepted Answer

A)  cleavage of RISCs by endonucleases. 
B)  cleavage of functional mRNA within the cytoplasm. 
C)  cleavage of pre-mRNA in the nucleus. 
D)  cutting and processing of double-stranded RNA by Dicer enzymes. 
E)  cutting and processing of double-stranded RNA by Slicer enzymes. 
A)  cleavage of RISCs by endonucleases. 
B)  cleavage of functional mRNA within the cytoplasm. 
C)  cleavage of pre-mRNA in the nucleus. 
D)  cutting and processing of double-stranded RNA by Dicer enzymes. 
E)  cutting and processing of double-stranded RNA by Slicer enzymes.

Question 15

A boundary element is also known as a(n):

Accepted Answer

A)  insulator. 
B)  repressor. 
C)  enhancer. 
D)  coactivator. 
E)  mediator. 
A)  insulator. 
B)  repressor. 
C)  enhancer. 
D)  coactivator. 
E)  mediator.

Question 16

Over the past decade, a significant finding in biology has been the identification of miRNAs and siRNAs and their role in regulating the development of many multicellular organisms. Briefly describe the four different ways these small RNAs influence gene expression.

Accepted Answer

1. Post-transcriptional gene silencing:

Question 17

A mutation in the gene for the yeast regulatory protein GAL4 causes yeast to grow poorly on galactose. What is the function of GAL4?

Accepted Answer

A)  It is a substrate that binds and activates a transcriptional activator. 
B)  It is a product that binds and activates a transcriptional repressor. 
C)  It is a transcriptional activator for the galactose-digesting enzyme gene. 
D)  It is a transcriptional repressor that prevents expression of yeast galactose-digesting enzymes. 
E)  It is an enzyme that metabolizes galactose. 
A)  It is a substrate that binds and activates a transcriptional activator. 
B)  It is a product that binds and activates a transcriptional repressor. 
C)  It is a transcriptional activator for the galactose-digesting enzyme gene. 
D)  It is a transcriptional repressor that prevents expression of yeast galactose-digesting enzymes. 
E)  It is an enzyme that metabolizes galactose.

Question 18

When regions around genes become sensitive to the enzyme DNase I, this is an indication that those regions are:

Accepted Answer

A)  becoming transcriptionally active. 
B)  becoming more condensed. 
C)  binding to the single-strand binding proteins. 
D)  destabilizing and transcriptionally inactive. 
E)  becoming highly methylated by a methylase. 
A)  becoming transcriptionally active. 
B)  becoming more condensed. 
C)  binding to the single-strand binding proteins. 
D)  destabilizing and transcriptionally inactive. 
E)  becoming highly methylated by a methylase.

Question 19

Which of the following statements about histones and gene expression is CORRECT?

Accepted Answer

A)  In a general sense, highly condensed DNA bound with histone proteins represses gene expression. 
B)  Acetylation involves the addition of acetyl groups to histone proteins, and it usually results in repression of transcription. 
C)  Addition of methyl groups to the tails of histone proteins always results in activation of transcription. 
D)  Histone code refers to the modification that takes place on the globular domain of the octamer histone core. 
E)  Phosphorylation of cytosines generally leads to increase in transcription.. 
A)  In a general sense, highly condensed DNA bound with histone proteins represses gene expression. 
B)  Acetylation involves the addition of acetyl groups to histone proteins, and it usually results in repression of transcription. 
C)  Addition of methyl groups to the tails of histone proteins always results in activation of transcription. 
D)  Histone code refers to the modification that takes place on the globular domain of the octamer histone core. 
E)  Phosphorylation of cytosines generally leads to increase in transcription..

Question 20

mRNAs are degraded by enzymes called:

Accepted Answer

A)  DNAse I. 
B)  ribozymes. 
C)  heat-shock proteins. 
D)  silencers. 
E)  ribonucleases. 
A)  DNAse I. 
B)  ribozymes. 
C)  heat-shock proteins. 
D)  silencers. 
E)  ribonucleases.

Exam 17: Control of Gene Expression in Eukaryotes

What are four things that influence the stability of eukaryotic mRNAs?

Which of the following eukaryotic gene regulatory mechanisms acts after transcription has been initiated?

What type of cellular activity is known to occur within P bodies?

What are three ways in which gene regulation is accomplished by modifying the structure of chromatin?

Which of the following mechanisms does NOT involve siRNA- and miRNA-based gene regulation?

Consider the regulation of galactose metabolism through GAL4. Which of the following would result from a mutation that allowed GAL3 to bind to GAL80 in the absence of galactose?

Although operons are not common in eukaryotes, eukaryotic genes may be activated by the same stimulus. Which of the following DNA regulatory sequences makes this coordinated gene expression possible?

Alternative splicing is known to be important in the regulation of the:

In which part of the mRNA does degradation generally begin?

Suppose a scientist discovered a mutant strain of C. elegans worms that had lost the ability to regulate gene expression via RNA interference mechanisms. Which of the following might she predict is a possible source of this defect?

Which of the following sequences or molecules is LEAST relevant to the assembly of the basal transcription apparatus for transcription?

RITS consists of:

Which of the following facts about eukaryotic gene regulation is TRUE?

siRNAs and miRNAs are produced by the:

A boundary element is also known as a(n):

Over the past decade, a significant finding in biology has been the identification of miRNAs and siRNAs and their role in regulating the development of many multicellular organisms. Briefly describe the four different ways these small RNAs influence gene expression.

A mutation in the gene for the yeast regulatory protein GAL4 causes yeast to grow poorly on galactose. What is the function of GAL4?

When regions around genes become sensitive to the enzyme DNase I, this is an indication that those regions are:

Which of the following statements about histones and gene expression is CORRECT?

mRNAs are degraded by enzymes called:

Introduction to Genetics

Chromosomes and Cellular Reproduction

Basic Principles of Heredity

Sex Determination and Sex-Linked Characteristics

Extensions and Modifications of Basic Principles

Pedigree Analysis, Applications, and Genetic Testing

Linkage, Recombination, and Eukaryotic Gene Mapping

Chromosome Variation

Bacterial and Viral Genetic Systems

DNA: the Chemical Nature of the Gene

Chromosome Structure and Organelle Dna

DNA Replication and Recombination

Transcription

Rna Molecules and Rna Processing

The Genetic Code and Translation

Control of Gene Expression in Prokaryotes

Gene Mutations and Dna Repair

Molecular Genetic Analysis and Biotechnology

Genomics and Proteomics

Epigenetics

Developmental Genetics and Immunogenetics

Cancer Genetics

Quantitative Genetics

Population Genetics

Evolutionary Genetics

Filters