Chapter 14
Which of the following is a common modification that affects the structure of DNA?
Methylation
In order for transcription of protein coding genes in eukaryotes to begin, the promoter must have several key features. What are they?
TATA box, regulatory elements, transcriptional start site
What is the CAP site for the lac operon?
The sequence of nucleotides that is recognized by an activator protein
What is the function of the genes encoded by the trp operon?
The synthesis of the amino acid tryptophan
Both prokaryotes and eukaryotes use _______ proteins to regulate the process of transcription.
activator and repressor
The genes in the trp operon encode enzymes that make the amino acid
tryptophan
Match each protein or group of proteins with its role in transcription. RNA polymerase general transcription factors activators
- synthesis of RNA from a DNA template - required for binding to the core promoter and initiating transcription - binding to enhancer sequences and interactions with other proteins
Sequence the steps that activator proteins take to promote the unraveling of compact chromatin at the site of gene transcription, listing the first step at the top of the list.
- transcriptional activator binds to an open enhancer site - activators recruit chromatin remodeling proteins - compacted chromatin is loosened - trancription occurs
What is an operon?
A cluster of genes under the transcriptional control of a single promoter
How do activators and repressors regulate the function of RNA polymerase in eukaryotes?
Activators and repressors interact with GTFs or mediator proteins.
How do activator proteins diminish the level of chromatin compaction at the site of the gene that is to be transcribed?
Activators bind to an enhancer site and then recruit other proteins to unravel and loosen the packed chromatin.
Which of the following is a form of gene regulation in which a eukaryotic pre-mRNA can be processed to produce more than one mature RNA?
Alternative splicing
The lac operon is also under positive control by an activator protein called what?
CAP
An activator protein recognizes the ______ of the lac operon.
CAP site
The enzyme _________________ ________________ is responsible for covalently attaching methyl groups to DNA.
DNA methylase
True or false: In multicellular organisms, genes are regulated in the same way to ensure that gene expression levels are constant regardless of cell type or developmental stage.
False
______ is the main protein that delivers oxygen to cells of a mammal's body.
Hemoglobin
How does allolactose affect the lac repressor protein?
It binds to the repressor protein and prevents it from binding to the operator site of the lac operon.
What is the effect of low levels of tryptophan on the transcription of the trp operon?
Low levels of tryptophan will result in high levels of transcription.
What are regulatory transcription factors?
Proteins that bind to DNA and affect the transcription of one or more genes
The lac repressor protein prevents the enzyme _________________ __________________ from transcribing the genes in the lac operon.
RNA polymerase
Why are interactions between RNA polymerase II and GTFs important for transcription in eukaryotes?
RNA polymerase II and GTFs must interact for the polymerase to bind properly at the core promoter site of the DNA.
How can gene regulation be specific?
Specific genes differ in expression levels from cell to cell. Specific genes are expressed at different developmental stages. Specific genes are expressed only in certain cells.
The two components that make up the core promoter are the _________________ box and the transcriptional start _________________.
TATA / site
What are the three features common to most promoters that are needed for the initiation of transcription of protein coding genes in eukaryotes?
TATA box Transcriptional start site Regulatory elements
What is chromatin?
The complex formed by DNA and its associated proteins
When are the genes involved in lactose metabolism in E. coli expressed and when are they turned off?
The genes for lactose metabolism are expressed when lactose is present but not when it is absent.
What is the function of the genes that are expressed in the lac operon of E. coli?
The metabolism of lactose
What is cell differentiation?
The process by which cells become specialized in different types
What is the role of the repressor protein in the transcription of the trp operon?
The repressor protein binds to the operator site and prevents the transcription of the trp operon.
What is the function of ATP-dependent chromatin-remodeling complexes?
They cause a change in the locations and/or compositions of nucleosomes
At what levels does gene regulation occur in prokaryotes?
Transcription Post-translation Translation
A nucleosome-free region (NFR) is:
a site on a chromosome that is missing nucleosomes
Match the features of transcriptional regulation on the left to the organisms using them on the right.
activator and repressor proteins regulate genes---> prokaryotes and eukaryotes genes organized individually----> eukaryotes genes organized in operons----> prokaryotes
When the sugar _____ , binds to the repressor protein, this causes a conformational change that prevents the repressor from binding to the _____ site.
allolactose / operator
The process whereby different transcripts are made from a single gene is called
alternative splicing
DNA and its associated proteins form a compact structure called:
chromatin
Proteins that use energy from ATP hydrolysis to change the locations and compositions of nucleosomes are called ATP-dependent _____________-______________ complexes.
chromatin remodelling
Cell ______ is the process by which cells become specialized into particular types.
differentiation
Polycistronic mRNA:
encodes more than one protein
The process in which the information in a gene is made into a functional gene product, such as an RNA molecule or a protein, is termed gene
expression
Many eukaryotic genes are flanked by a nucleosome- ________________ __________________, which is a site that is missing nucleosomes.
free region
The functional product of genes arises from what process?
gene expression.
In mammals, the protein __________________ delivers oxygen to body cells.
hemoglobin
The __________________ ____________________ hypothesis states that covalent modifications of histones are a language directing interactions between histones and chromatin.
histone code
Transcription of the trp operon is ______ when levels of tryptophan are low in the cell.
increased
In mammals, when iron levels are high, iron binds to the iron regulatory protein, which results in:
increased translation of ferritin
The following diagram shows which type of operon?
lac operon in the absence of lactose
This diagram is a representation of which type of operon?
lac operon in the presence of lactose
The genes found in the lac operon of E.coli are used for the metabolism of
lactose
In E. coli, the genes required to metabolize lactose are expressed:
only when lactose is present
In the lac operon, the _______ is the DNA sequence at which the lac repressor binds.
operator
The lacO site of the lac operon is called the _________________ and is the site where the repressor protein binds.
operator
A(n) ___________________ is a cluster of genes that are part of a single transcription unit that is under the control of a single promoter.
operon
An mRNA that encodes more than one protein is called ________________ mRNA.
polycistronic, poly-cistronic, or poly cistronic
The catabolite activator protein (CAP) is involved in ______ control of the lac operon.
positive
Bacteria and eukaryotes can regulate genes at the level of transcription. In eukaryotes, gene expression is also commonly regulated at the levels of RNA _________________ and translation.
processing or modification
Regulatory transcription factors influence the expression of genes by binding directly to DNA at or near the _______________ site and affect the rate of transcription.
promoter
Regulation of prokaryotic gene expression typically involves all of the following mechanisms EXCEPT:
regulation of RNA processing
The trp operon is regulated by a(n) _____________ protein that is encoded by the trpR gene.
repressor
What molecules can influence transcription by binding to enhancers or silencers?
repressors and activators
The transcription of the lac operon genes is inhibited when the lac repressor protein binds to:
the lac operator
According to the histone code hypothesis, proteins recognize histones based on:
their covalent modifications
What are the two components of the core promoter?
transcriptional start site TATA box
In mammals, iron toxicity is prevented by regulating the ______ of ferritin.
translation
Eukaryotic gene expression can be regulated at which levels?
translation RNA modification transcription
