Cell Biology Exam 1
Which of the following statements about cancer is FALSE
A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell
The figure below is an example of
A scanning electron micrograph
Tight junctions
Are formed from claudins and occludins
miRNAs, tRNAs, and rRNAs all
do not code for proteins
cells that are specialized for the secretion of proteins are likely to have which of the following features
enlarges endoplasmic reticulum
The N-terminal tail of histone H# can be extensively modified, and depending on the number location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation
gene silencing
The owners of a local bakery ask for your help in improving a special yeast strain they use to make bread. They would like you to help them design experiments using RNA interference to turn off genes, to allow them to test their hypothesis that certain genes are important for the good flavors found in their bread. Of the components in the following list, which is the most important to check for in this yeast strain if you'd like this project to succeed?
genes in the genome that code for RISC proteins
Combinatorial control of gene expression
involves groups of transcriptional regulators working together to determine the expression of a gene
Paneth cells in the intestine
is a specialized secretory cell
Bone marrow
is derived from mesoderm
An siRNAs complexed with the RISC proteins
is double stranded
The long noncoding RNA Xist
is important for the formation of highly condensed heterochromatin on the chromosome
Beta-catenin
is unstable in the presence of APC
A stem cell divides into two daughter cells. One of the daughter cells goes on to become a terminally differentiated cell. What is the typical fate of the other daughter cell?
it remains a stem cell
The classic "beads-on-a-string" structure is the most decondensed chromatin structure possible and is produced experimentally. Which chromatin components are not retained when this structure is generated?
linker histones
Cadherins
mediate cell-cell attachments through homophilic interactions
In the following diagram the protein labeled 2 represents the
mediator
Which of the following statements about DNA methylation in eukaryotes is FALSE
methylation of DNA attracts proteins that block gene expression
Which of the following organelles has bother an outer and inner membrane
mitochondrion
The proteins that links cadherins to the intermediate filaments in desmosomes include
plakoglobin
When a terminally differentiated cell in an adult body dies, it can typically be replaced in the body by a stock of
proliferating precursor cells
Ras is a GTP-binding protein that is often defective in cancer cells. A common mutation found in cancer cells causes Ras to behave as though it were bound to GTP all the time, which will cause cells to divide inappropriately. From this description, the normal Ras gene is
proto-oncogene
Eukaryotic RNA polymerase III is responsible for transcribing
tRNA
Which of the following examples does NOT describe a mechanism of post-transcriptional control of gene expression
the action of the RNA component of telomerase
A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals., while a white blood cell defends the body against infection. This is because
the neuron expresses some mRNAs that the white blood cell does not
The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the
transcription of genes transcribed by RNA polmerase II
Using genetic engineering techniques, you remove the sequences that code for the ribosome-binding sequences of the bacterial LacZ gene. the removal of these sequences will lead to
translational inhibition of the LacZ mRNA
Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by __________________.
using the energy of ATP hydrolysis to move nucleosomes
Question 4: you are interested in examining the Psf gene
Both MetA and MetC
Enhancers can act over long stretches of DNA but are specific about which genes they affect. How do eukaryotic cells prevent these transcription regulators from looping in the wrong direction and inappropriately turning on the transcription of a neighboring gene
Chromosome loop-forming proteins arrange the DNA into topological associated domains such that individual genes and their associated enhancer binding regions are in proximity
The MyoD transcriptional regulator is normally found in differentiating muscle cells and participates in the transcription of genes that produce muscle-specific proteins such as those needed in contractile tissue. Amazingly, expression of MyoD in fibroblasts causes these cells derived from skin connective tissue to produce proteins normally only seen in muscles. However, some other cell types do not transcribe muscle-specific genes when MyoD is expressed in them. Which of the following statements below is the best explanation of why MyoD can cause fibroblasts to express muscle - specific genes
During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells
Which of the following is NOT a general mechanism that cells use to maintain stable patterns of gene expression as cells divide
Proper segregation of housekeeping proteins when cells divide
Which of the following statements is FALSE?
Proteoglycans are a major component of compact connective tissues but are relatively unimportant in watery tissues such as the jellylike substance in the interior of the eye
Which type of junction contributed the most to the polarization of epithelial cells
Tight Junctions
Which of the following statements about how fruit flies can develop an eye in the middle of a leg is TRUE?
When the Ey gene is introduced into the cells that would normally give rise to the leg, the transcription regulators used to control its expression in the leg are different from those that are normally used to control Ey expression in the eye
Cancer cells
are abnormally invasive
The individual subunits of a gap junction
are connexins
Hemidesmosomes are important for
attaching epithelial cells to extracellular matrix
How are most eukaryotic transcription regulators able to affect transcription when their binding sites are far from the promoter?
by looping out the intervening DNA between their binding site and the promoter
Induced pluripotent stem (iPS) cells
can be created by the expression of a set of key genes in most somatic cell types, including cells derived from adult tissues
Operons
contain a cluster of genes transcribed as a single mRNA
Prokaryotic gene expression can be regulated by
controlling how often a gene is transcribed
The octameric histone core is composed of four different histone proteins, assmbled in a stepwise manner. Once the core octamer has been formed, DNA wraps around it to form nucleosome core particle. Which of the following histone proteins does NOT form part of the octameric core?
H1
Which of the following statements about nucleosomes is TRUE
Histone acetyltransferases affect transcription by adding acetyl groups to histones that can bind proteins that promote transcription
Cellulose
Is assembled into extracellular matrix
Which of the following statements about the Lac Operon is FALSE
The Lac repressor binds when lactose is present in the cell
You are studying a set of mouse genes whose expression increases when cells are exposed to the hormone cortisol, and you believe that the same cortisol-responsive transcriptional activator regulates all of these genes. If your hypothesis is correct, which of the following statements below should be TRUE?
The cortisol-responsive genes share a DNA sequence in their regulatory regions that binds the cortisol-responsive transcriptional activator
The cytoskeletal element with the narrowest diameter is
actin filaments
Which type of junction involves a connection to the actin cytoskeleton
adherens junctions
Which of the following statements about iPS cells is FALSE
iPS cells made from mouse cells can differentiate into almost any human cell type