Chapter 8 Flashcards
(32 cards)
Which of the following statements is NOT true about the differences between liver cells and kidney cells in the same organism?
A)They contain the same genes, but express them differently.
B)They contain different genes.
C)They contain different sets of proteins.
B
A typical differentiated human cell will express how many of its approximately 25,000 genes?
From 5000 to 15,000 genes
T/F A cell can change the expression of its genes in response to external signals.
A cell can change the expression of its genes in response to external signals.
T/F: Different cell types that respond to the same hormone usually turn on the same sets of genes.
False
Although all of the steps involved in expressing a gene can in principle be regulated, for most genes the most important point of control is:
transcription initiation
A gene regulatory protein usually binds to which groove in the DNA double helix?
Major groove
When a gene regulatory protein binds to DNA, its most important interactions occur with which parts of the DNA?
Base pairs
T/F When a gene regulatory protein binds to DNA, it typically disrupts the hydrogen bonding between base pairs.
False
Which of the following is the initiation site in a gene?
The part of a promoter where transcription actually begins
In bacteria when transcription regulators bind to regulatory DNA sequences close to where RNA polymerase binds, they:
activate or repress transcription of the gene depending
upon where they are located relative to the promoter.
What is the definition of an operon?
A set of genes (found in bacteria but not eukaryotes) that
is transcribed into a single mRNA.
Which of the following statements accurately describes the expression of the repressor protein of the tryptophan operon?
The gene for the tryptophan repressor is expressed
constitutively.
In the bacterial cell, the tryptophan operon encodes the genes needed to synthesize tryptophan. When the concentration of tryptophan inside the cell is high:
it activates the tryptophan repressor, which shuts down the tryptophan operon.
Many activator proteins must do what before they can interact with DNA?
Bind to a metabolite or other small molecule
Which of the following describes the lac operon in E. coli when lactose, but not glucose, is present in the culture medium?
CAP, but not the lac repressor, is bound to the lac operon’s regulatory DNA, and the lac operon is expressed.
Which of the following describes the lac operon in E. coli when both lactose and glucose are present in the culture medium?
Neither CAP nor the lac repressor is bound to the lac
operon’s regulatory DNA, and the lac operon is not expressed.
In eukaryotes, where do transcription regulators bind?
Either upstream or downstream from a gene
Which of the following is false?
A: Eukaryotic gene activator proteins stimulate transcription initiation by recruiting proteins that modify chromatin structure.
B: Eukaryotic gene activator proteins stimulate transcription initiation by aiding in the assembly of general transcription factors and RNA polymerase at the promoter.
C: Eukaryotic gene activator proteins stimulate transcription initiation by recruiting a DNA polymerase to the promoter.
C
T/F The general transcription factors that assemble at a eukaryotic promoter are different, depending on the specific gene being transcribed by polymerase II.
False
How many different gene regulatory proteins work together to control a typical human gene?
Dozens
T/F Even though control of eukaryotic gene expression is combinatorial, the effect of a single gene regulatory protein can still be decisive in switching any particular gene on or off.
True
T/F Differentiated cells in multicellular organisms require hormonal input to ‘remember’ what type of cell they should be.
False
T/F Transcription regulators can be used to convert one differentiated cell type into another cell type, but NOT to convert differentiated cells into a less differentiated, pluripotent stem cells.
False
T/F A single transcription regulator, if expressed in the appropriate precursor cell, can trigger the formation of a specialized cell type or even an entire organ.
True
