BIO 203 Lecture 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.

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?

enlarged endoplasmic reticulum

The N-terminal tail of histone H3 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

Of the components in the following list, which is the most important to check for in this yeast strain if you would like this project to succeed?

genes in the genome that code for RISC proteins

Combinatorial control of gene expression

involves groups of transcription regulators working together to determine the expression of a gene.

Paneth cells in the intestine:

is a specialized secretory cell.

Cellulose:

is assembled into extracellular microfibrils.

Bone marrow:

is derived from mesoderm.

The long noncoding RNA Xist

is important for the formation of highly condensed heterochromatin on the X 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 most likely to be lost when this structure is generated?

linker DNA

Cadherins

mediate cell-cell attachments through cadherin-cadherin interactions on adjacent cells.

Which of the following organelles has both an outer and an 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 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 a/an

proto-oncogene.

Eukaryotic RNA polymerase III is responsible for transcribing:

tRNA.

An siRNAs complexed with the RISC proteins:

targets foreign RNA or RNA that could be detrimental to the cell.

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.

Which type of junction contributes the most to the polarization of epithelial cells?

tight junctions

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 polymerase 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.

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 domains such that individual genes and their associated enhancer binding regions are in proximity.

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 statements about proteoglycans is FALSE?

Proteoglycans are composed of amino acids and nucleic acids.

Which of the following is NOT a general mechanism that cells use to maintain stable patterns of gene expression as cells divide?

a positive feedback loop, mediated by a transcriptional regulator that activates transcription of its own gene in addition to other cell-type-specific genes

The figure below is an example of:

a scanning electron micrograph.

Cancer cells:

are abnormally invasive.

The individual subunits of a gap junction:

are connexins.

Tight junctions

are formed from claudins and occludins.

Hemidesmosomes are important for

attaching epithelial cells to the extracellular matrix.

You are interested in examining the Psf gene. It is known that Psf is normally produced when cells are exposed to high levels of both calcium (Ca2+) and magnesium (Mg2+). MetA, MetB, and MetC are important for binding to the promoter of the Psf gene and are involved in regulating its transcription. MetA binds to the "A" site in the promoter region, MetB to the "B" site, and MetC to the "C" site. You create binding-site mutations in the A, B, and C sites and observe what happens to transcription of the Psf gene. Your results are summarized in Table 8-12.

both MetA and MetC

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:

all of the above

The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. Once the core octamer has been formed, DNA wraps around it to form a 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 histone tails that can bind proteins that promote transcription.

Which of the following statements about DNA methylation in eukaryotes is FALSE?

Immediately after DNA replication, each daughter helix contains one methylated DNA strand, which corresponds to the newly synthesized strand.

Which of the following statements about the Eyeless transcriptional regulator is FALSE?

The Eyeless transcription factor itself must turn on the expression of every eye-specific gene in the fly.

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.