ESSENTIAL CELL BIOLOGY- CHAPTER
#8 EXAM QUESTIONS AND ANSWERS
How does transcription regulators work? - ANSWER-They recognize a specific
nucleotide sequence because they fit tightly with the surface feature of the double helix.
In most cases, the protein inserts into the major groove of the DNA helix and makes a
series of intimate molecular contacts with the nucleotide pairs within the groove. Most of
these transcription regulators bind to the DNA helix as dimers.
leucine zipper - ANSWER-type of transcription factor in which repeating leucines form
an interaction domain.
What are operons? - ANSWER-In prokaryotic cells, a cluster of genes under control of a
promoter. They are rare in eukaryotes
What is the operon structure and function in a bacteria for tryptophan? - ANSWER-
Within the operon's promoter is a short DNA sequence, called the operator. It gets
recognized by a transcription regulator. When the regulator binds to the operator, it
blocks access of RNA polymerase to the promoter, preventing transcription.
What is a transcriptional repressor protein? - ANSWER-A regulatory protein that is
bound to the promoter DNA to prevent RNA polymerase from binding
-negative transcriptional control. It switches off genes.
transcriptional activators - ANSWER-Stimulate transcription apparatus at the core
promoter
Can act indirectly through coactivators. Usually needs the help of other proteins to help
bind to DNA.
Enhancers - ANSWER-A DNA sequence that recognizes certain transcription factors
that can stimulate transcription of nearby genes. Found in eukaryotes. These activator
proteins could enhance transcription even when they are bound thousand of nucleotide
pairs away from the gene's promoter. They also work when bound wither upstream or
downstream of a gene. This is because the nucleotides between the enhance and
promoter can loop out.
mediator complex - ANSWER-A complex of proteins that interacts with the Pol II
complex and allows transcription to begin.
What is the role of a nucleosome in transcription? - ANSWER-A nucleosome can inhibit
the initiation of transcription if they are positioned over a promoter. This is to help
prevent leaky gene expression by blocking the initiation of transcription.
, histone deacetylases - ANSWER-proteins that function to remove the acetyl groups
from histones
make the chromatin in a more closed conformation
overall decreases the gene expression levels of the cell
cell memory - ANSWER-The ability of differentiated cells and their descendants to
maintain their identity.
Is it unusual in plants and animals to have their regulatory DNA sequence for a gene be
dotted over tens of thousands of nucleotide pairs. - ANSWER-No it is not. This is
because of spacer DNA that do not directly recognize transcription regulators.
True or false: most eukaryotic regulators work alone. - ANSWER-False. They usually
work in a committee that are necessary to express a gene in the right place, in the right
cell type, in response to the right conditions, at the right time, in the right amount.
combinatorial control - ANSWER-Describes the way in which groups of transcription
regulators work together to regulate the expression of a single gene.
The difference in how bacteria coordinate the expression of genes vs how eukaryotes
do it. - ANSWER-Bacteria coordinate the expression of a set of genes is by having them
clustered together in an operon under the control of a single promoter
Eukaryotes will not have that. Instead they will have a single protein that can complete
the combination of transcription regulators for several different genes. As long as the
different genes contain regulatory DNA sequences that are recognized by the same
transcription regulator they can be turned on or off at once.
What are other uses of combinatorial control for eukaryotes? - ANSWER-They allow
eukaryotes to diversify into particular types of cells during embryonic development.
What is the significance of MyoD in muscle cells - ANSWER-The addition of it
completes the unique combination required to direct the cells to become muscle
pluripotent stem cells - ANSWER-Stem cells that can become almost all types of tissues
and cells in the body.
induced pluripotent stem cells - ANSWER-a pluripotent stem cell that was generated by
manipulation of a differentiated somatic cell
These cells are derived from normal cells that have been coaxed into de differentiating
via transcription regulators
terminally differentiated - ANSWER-cell has become a certain cell type and will no
longer divide. These include skeletal muscle and neurons
#8 EXAM QUESTIONS AND ANSWERS
How does transcription regulators work? - ANSWER-They recognize a specific
nucleotide sequence because they fit tightly with the surface feature of the double helix.
In most cases, the protein inserts into the major groove of the DNA helix and makes a
series of intimate molecular contacts with the nucleotide pairs within the groove. Most of
these transcription regulators bind to the DNA helix as dimers.
leucine zipper - ANSWER-type of transcription factor in which repeating leucines form
an interaction domain.
What are operons? - ANSWER-In prokaryotic cells, a cluster of genes under control of a
promoter. They are rare in eukaryotes
What is the operon structure and function in a bacteria for tryptophan? - ANSWER-
Within the operon's promoter is a short DNA sequence, called the operator. It gets
recognized by a transcription regulator. When the regulator binds to the operator, it
blocks access of RNA polymerase to the promoter, preventing transcription.
What is a transcriptional repressor protein? - ANSWER-A regulatory protein that is
bound to the promoter DNA to prevent RNA polymerase from binding
-negative transcriptional control. It switches off genes.
transcriptional activators - ANSWER-Stimulate transcription apparatus at the core
promoter
Can act indirectly through coactivators. Usually needs the help of other proteins to help
bind to DNA.
Enhancers - ANSWER-A DNA sequence that recognizes certain transcription factors
that can stimulate transcription of nearby genes. Found in eukaryotes. These activator
proteins could enhance transcription even when they are bound thousand of nucleotide
pairs away from the gene's promoter. They also work when bound wither upstream or
downstream of a gene. This is because the nucleotides between the enhance and
promoter can loop out.
mediator complex - ANSWER-A complex of proteins that interacts with the Pol II
complex and allows transcription to begin.
What is the role of a nucleosome in transcription? - ANSWER-A nucleosome can inhibit
the initiation of transcription if they are positioned over a promoter. This is to help
prevent leaky gene expression by blocking the initiation of transcription.
, histone deacetylases - ANSWER-proteins that function to remove the acetyl groups
from histones
make the chromatin in a more closed conformation
overall decreases the gene expression levels of the cell
cell memory - ANSWER-The ability of differentiated cells and their descendants to
maintain their identity.
Is it unusual in plants and animals to have their regulatory DNA sequence for a gene be
dotted over tens of thousands of nucleotide pairs. - ANSWER-No it is not. This is
because of spacer DNA that do not directly recognize transcription regulators.
True or false: most eukaryotic regulators work alone. - ANSWER-False. They usually
work in a committee that are necessary to express a gene in the right place, in the right
cell type, in response to the right conditions, at the right time, in the right amount.
combinatorial control - ANSWER-Describes the way in which groups of transcription
regulators work together to regulate the expression of a single gene.
The difference in how bacteria coordinate the expression of genes vs how eukaryotes
do it. - ANSWER-Bacteria coordinate the expression of a set of genes is by having them
clustered together in an operon under the control of a single promoter
Eukaryotes will not have that. Instead they will have a single protein that can complete
the combination of transcription regulators for several different genes. As long as the
different genes contain regulatory DNA sequences that are recognized by the same
transcription regulator they can be turned on or off at once.
What are other uses of combinatorial control for eukaryotes? - ANSWER-They allow
eukaryotes to diversify into particular types of cells during embryonic development.
What is the significance of MyoD in muscle cells - ANSWER-The addition of it
completes the unique combination required to direct the cells to become muscle
pluripotent stem cells - ANSWER-Stem cells that can become almost all types of tissues
and cells in the body.
induced pluripotent stem cells - ANSWER-a pluripotent stem cell that was generated by
manipulation of a differentiated somatic cell
These cells are derived from normal cells that have been coaxed into de differentiating
via transcription regulators
terminally differentiated - ANSWER-cell has become a certain cell type and will no
longer divide. These include skeletal muscle and neurons
