Cell Exam #4-2014 - Franklin College

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Cell Biology exam #4-2014

Name___Key_______________ Lab Section_______

Multiple choice. Choose the best answer (2 points each)

1.___E__Bacteria can respond to changes in their environment by: A) regulating the activity of their enzymes; B) regulating gene expression by the operon model; C) turning off and on genes at critical times; D) the action of repressor proteins; E) all of the above.

2.____D_This technology allows researchers to compare gene expression in two different tissues such as normal and cancerous breast tissue: A) Rna-interference ; B) distal control elements; C) epigenetics;

D) DNA microarrays; E) operons

3.___E__ The operator, promotor, and repressor genes are: A) all possible activators of distal control elements that regulate gene expression; B) are examples of noncoding RNA, C) are involved in the posttranscriptional regulation of gene expression; D) are all part of an operon; E) none of the above.

4. __A___Beta-galactosidase is : A) an inducible enzyme; B) coded for by a structural gene in the trpoperon; C) normally produced unless the level of galactose is too high; D) is an important structural part of a nucleosome; E) a structural gene

5.__C___DNA methylation patterns (which affect gene expression) can be passed from parent to child

(or even grandparents to grandchildren) and affect the traits of offspring. This is an example of: A) post-transcriptional regulation of gene expression; B) the action of noncoding rna in the regulation of gene expression; C) epigenetics; D) post translational regulation of gene expression; E) positive gene regulation.

6.___A__Which of the following can turn a repressor protein from its inactive (can’t bind operator) to its active state (can bind to the operator)? A) binding the appropriate co-repressor; B) histone acetylation;

C) histone deacetylation; D) cAMP; E) binding the appropriate enhancer (specific transcription factor)

7.__C___In the lac operon: A) the normal status is that the structural genes are “on”; B) lactose turns on the regulatory gene; c) the operator is blocked unless (allo)lactose is present; D) the co-repressor binds to the operator; E) the structural and regulatory genes directly interact to allow the RNA polymerase to bind to the promotor.

8.__B___Which of the following is most closely associated with enhancers and their associated distal control elements? A) alternative RNA processing; B) specific transcription factors (activators) and DNA bending proteins; C) noncoding RNA; D) RNA interference; E) Barr bodies

9.__B__This condition favors the active transcription of genes: A) DNA in the heterochromatin state;

B) histone acetylation; C) Barr bodies; D) the presence of si-Rna; E) DNA in the highly compacted state.

10.__B___Camp and CAP are involved in: A) RNA-interference; B) positive regulation of the lac-operon;

C) the formation of euchromatin; D) DNA methylation; E) m-rna degredation.

11. ___C__This phenomenon influences gene expression by degrading m-rna or inhibiting its translation.

It was discovered by researchers trying to make a very purple petunia: A) Reactivation of density dependent inhibition; B) lysogeny; C) RNAi (RNa interference); D) transformation; E) apoptosis

12.___E__PGDF: A) is a specific transcription factor that binds to an enhancer; B) is the co-repressor in the lac operon; C) turns euchromatin into heterochromatin; D) is an oncogene; E) stimulates cells to move past the G1 check point in the cell cycle.

13.___D__Which of the following molecules do not play a role in the regulation of the cell cycle? A)

CDK (cyclin dependent kinase); B) MPF (maturation promoting factor); C) cyclins; D)P-53; E) all of the above are involved.

14.__D___Nonmutated versions of genes that code for growth factors: A) are proto-oncogenes; B) are tumor suppressor genes; C) are found in non-cancerous cells ; D) A and C; E) all of the above.

15.___C__Cancer cells: A) demonstrate density dependent inhibition and anchorage dependence;

B) normally divide 20-50 times in culture and then stop dividing; C) may convey a growth factor’s signal without the presence of the growth factor; D) are rarely formed in the human body; E) become less likely to be formed with age.

16._C____Protooncogens can be converted into oncogenes by all of the following mechanisms except:

A) movement of DNA (translocation) within the genome; B) amplification of a proto-oncogene;

C) density dependent inhibition; D) a point mutations in the proto-oncogene or its control elements.

17.___E__ Forms of the Ras protein found in tumors usually cause which of the following?

A) DNA replication to stop; B) DNA replication to be hyperactive; C) cell-to-cell adhesion to be nonfunctional; D) cell division to cease; E) growth factor signaling to be hyperactive.

18.___B__Sometimes referred to as the “guardian angel of the cell”, the P-53 gene codes for proteins that: A) stimulate density dependent inhibition; B) activates suicide genes that cause apoptosis; C) turns proto-oncogenes into oncogenes; D) move the cell cycle past key checkpoints; E) are growth factors

19.___D__A mutation on the Ras gene: A) is associated with 50% of known breast cancers; B) inactivates a tumor suppressor gene; C) produces a protooncogene; D) can make a cell become cancerous; E) all of the above.

20.___E__Cancer can be caused by: A) spontaneous mutations; B) induced mutations; C) virus;

D) a defective P-53 gene; E) all of the above

21.___D__ The 1918 pandemic caused by the Spanish flu: A) was caused by an H5N1 virus; B) was caused by an antibiotic resistant strain of bacteria; C) only killed people in Spain; D) was caused by a virus that was normally restricted to birds but mutated so it could affect and be transmitted by humans;

E) made thousands ill but killed very few people.

22.____E_This medical treatment is not effective in treating viral diseases and relieving their symptoms:

A) antibiotics; B) drugs that enhance your immune system; C) protease inhibitors; D) vaccinations;

E) A and D.

23.__D___ H1N1: A) is a tumor suppressor gene; B) in an oncogene; C) is a specific transcription factor;

D) is a type A influenza virus; E) is a capsid protein

24.___A__Which of the following properties is inconsistent with being a virus? A) making your own ATP;

B) being only made up of DNA and protein; C) having either DNA or RNA but not both; D) being an obligate intracellular parasite; E) none of the above-all are consistent with being a virus.

25.__B___Because of this property of your immune system, vaccination is an effective method for preventing viral disease: A) self-assembly; B) memory; C) lysogeny; D) mutation; E) A and C.

26.___D__These infectious agents are made entirely of protein and cause disease by stimulating normal cellular proteins to misfold: A) provirus; B) neuraminidase; C) pandemic; D) prions; E) temperate phages

27.__C___All of the following can cause symptoms caused by a viral disease except: A) cell lysis;

B) oncogenes; C) restriction enzymes D) your immune system; E) toxins encoded by provirus.

28._E____Which of the following does not contribute to the development of an “emerging virus”?

A) increased air travel; B) the spread of existing viruses to new host species.; C) environmental disturbances; D) changes in social behavior and social norms; E) overuse of antibiotics

29.___D__ A bacterium is infected with an experimentally constructed bacteriophage composed of the

T2 phage protein coat and T4 phage DNA. The new phages produced will have

A) T2 protein and T4 DNA; B) T2 protein and T2 DNA; C) a mixture of the DNA and proteins of both phages; D) T4 protein and T4 DNA; E) T4 protein and T2 DNA.

30.__B___ RNA viruses such as HIV must carry with them certain enzymes (such as reverse transcriptase) because: A) host cells rapidly destroy the viruses; B) infected host cells lack enzymes that can replicate the viral genome; C) these enzymes translate viral mRNA into proteins; D) these enzymes penetrate host cell membranes; E) these enzymes cannot be made in host cells.

31.__D__ Which of the following accounts for someone who has had a herpesvirus-caused cold sore or genital sore getting flare-ups for the rest of his or her life?

A) re-infection by a closely related herpesvirus of a different strain; B) re-infection by the same herpesvirus strain; C) co-infection with an unrelated virus that causes the same symptoms; D) copies of the herpesvirus genome permanently maintained in host nuclei (provirus); E) copies of the herpesvirus genome permanently maintained in host cell cytoplasm

32.__E___ Most molecular biologists think that viruses originated from fragments of cellular nucleic acid such as transposons. Which of the following observations supports this theory?

A) Viruses contain either DNA or RNA; B) Viruses are enclosed in protein capsids rather than plasma membranes; C) Viruses can reproduce only inside host cells; D) Viruses can infect both prokaryotic and eukaryotic cells; E) Viral genomes are usually similar to the genome of the host cell.

33. (4 points each) Agree or disagree with the following statements. In either case, fully defend your answer.

A. There is an advantage of regulating gene expression using the operon strategy.

Agree-This allows bacteria to respond to changes in the environment and not waste resources making proteins that are not needed at that time such as inducible and repressible enzymes .

B. Once the genetic basis of colon cancer was determined, researchers understood that colon cancer was inconsistent with the model (hypothesis) of the multistep development of cancer.

Disagree-There are several identifiable steps in the development of colon cancer that involve successive mutations to tumor suppressor genes such as DCC, APC, and P-53. These mutations follow one another in a predictable stepwise fashion involving successive generations of cells.

C. A mutation that results in a cell being overly sensitive to PGDF can result in cancer.

Agree-PGDF is a growth regulator. If a cell responds excessively to this growth factor it may continuing dividing even if the growth factor levels are too low to stimulate cell division in a normal cell. This lead to the uncontrolled cell division characteristic of cancer cells.

D. RNA virus tend to have higher mutation rates than DNA virus.

Agree-RNA virus use RNA polymerase to copy their RNA genome into more RNA molecules. Unlike

DNA polymerase (which replicates DNA), RNA polymerase cannot self correct the inevitable mistakes in base pairing that happen during replication. This leads to mutation.

34. (10 points) Referring to the availability activators and the interaction of activators and enhancer control elements, explain how and why lens cells produce crystalline protein but not the protein albumin (which is commonly produced by liver cells) even though both cells types have the same genes.

Enhancers are DNA sequences that stimulate gene expression. They consist of several control elements each of which reacts with a specific activator (specific transcription factor). If the required activators are present in a cell, they bind to the control elements of the enhancer and this stimulates a

DNA bending protein to fold the DNA so that the enhancer (and the associated control elements with their bound activators) to be in close proximity to the gene promotor. The bound activators recruit mediator proteins and general transcription factors that allow RNA polymerase to attach to the gene premotor and transcription of the associated gene occurs. This transcription initiation complex consists of the RNA polymerase, mediator proteins, bound activators, and general and specific transcription factors.

In lens cells the required activators are present to form the initiation complex at the promotor of the crystalline protein gene but not the albumin gene. In liver cells the required activators are present to form the initiation complex at the promotor of the albumin gene but not the crystalline protein gene.

So the different cell types express different genes due to the presence or absence of specific activator molecules in the two different cell types.

A diagram would be helpful in showing this.

35. (10 points) Describe the features (steps) of a generalized animal virus lytic life cycle. Explain how the lysogenic life cycle differs from the lytic cycle you just described.

In the lytic cycle the following steps occur:

A.

Attachment-virus capsid proteins must bind to specific receptors on the host cell surface. No attachment, no infection.

B.

Entry-The virus is brought into the cytoplasm (usually by endocytosis). The capsid is digested

(uncoating) and the viral nucleic acid is now in the cell.

C.

Replication-the viral nucleic acid takes over the host cell’s process and directs it toward making viral nucleic acid and proteins using the host cell’s machinery

D.

Assembly-the viral nucleic acid and protein spontaneously comes together and forms new virus.

E.

Release-the newly assembled virus are released either by cell lysis or budding

In the lysogenic life cycle, the first two steps occur. Then the viral nucleic acid joins with the host DNA and becomes a provirus. Expression of the viral repressor gene produces a protein that inhibits the expression of all other viral genes. This, no new virus are formed but the viral nucleic acid is copied every time the host genome is copied.

If induction occurs, the provirus release from the host genome and a lytic cycle now begin.

Bonus (not optional points)-Each question is worth 1 point. The total bonus points are determined by subtracting the number of questions answered incorrectly (X 0.5) from the number of correct answers

(an unanswered question is not counted as being incorrect). The lowest grade you can get on the bonus section is 0 (so it can’t hurt your final score). Any bonus you receive on this exercise will be added to your final grade.

1.__E___

Which of the following series best reflects what we know about how the flu virus moves between species?

A) An avian flu virus undergoes several mutations and rearrangements such that it is able to be transmitted to other birds and then to humans.

B) The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected.

C) A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans.

D) An influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host.

E) An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates and is passed to a new species such as a bird, and the virus mutates and can be transmitted to humans.

2.___C__ A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?

A) The plants would develop some but not all of the symptoms of the TMV infection.

B) The plants would develop symptoms typically produced by viroids.

C) The plants would develop the typical symptoms of TMV infection.

D) The plants would not show any disease symptoms.

E) The plants would become infected, but the sap from these plants would be unable to infect other plants.

Use this information to answer questions 3-5

The herpesviruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can then reactivate, replicate again, and be infectious to others.

3)_____B If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected, which of the following would have the best chance of lowering the number of new cases of infection?

A) vaccination of all persons with preexisting cases

B) interference with new viral replication in preexisting cases

C) treatment of the HSV lesions to shorten the breakout

D) medication that destroys surface HSV before it gets to neurons

E) education about avoiding sources of infection

4) ____D_In electron micrographs of HSV infection, it can be seen that the intact virus initially reacts with cell-surface proteoglycans, then with specific receptors. This is later followed by viral capsids docking with nuclear pores. Afterward, the capsids go from being full to being "empty." Which of the following best fits these observations?

A) Viral capsids are needed for the cell to become infected; only the capsids enter the nucleus.

B) The viral envelope is not required for infectivity, since the envelope does not enter the nucleus.

C) Only the genetic material of the virus is involved in the cell's infectivity, and is injected like the genome of a phage.

D) The viral envelope mediates entry into the cell, the capsid enters into the nuclear membrane, and the genome is all that enters the nucleus.

E) The viral capsid mediates entry into the cell, and only the genomic DNA enters the nucleus, where it may or may not replicate.

5)_____C In order to be able to remain latent in an infected live cell, HSV must be able to shut down what process?

A) DNA replication

B) transcription of viral genes

C) apoptosis of a virally infected cell

D) all immune responses

E) interaction with histones

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