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