Biology- Ch.15 and 17

Some viruses can be crystallized and their structures analyzed. One such virus is yellow mottle virus, which infects beans. This virus has a single-stranded RNA genome containing about 6,300 nucleotides. Its capsid is 25-30 nm in diameter and contains 180 identical capsomeres. If the yellow mottle virus capsid has 20 facets, how many proteins form each facet?

9

Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells?

A specific combination of control elements in each genes enhancer coordinates the simultaneous activation of the genes

Two potential devices that eukaryotic cells use to regulate transcription are

DNA methylation and histone modification

Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following?

Eukaryotic exons may be spliced in alternative patterns

What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for DNA synthesis.

The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called

RNA interference

For a repressible operon to be transcribed, which of the following must occur?

RNA polymerase must bind to the promoter, and the repressor must be inactive

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the repressor gene (lac I), along with its promoter, to a position some several thousand base pairs away from its normal position, which will you expect to occur?

The lac operon will function normally

Which of the following statements describes the lysogenic cycle of lambda (λ) phage?

The phage genome replicates along with the host genome

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?

The plants would develop the typical symptoms of TMV infection

A researcher introduces double-stranded RNA into a culture of mammalian cells, and can identify its location or that of its smaller subsections experimentally, using a fluorescent probe. In addition, she finds what other evidence of this single-stranded RNA piece's activity?

The rate of accumulation of the polypeptide encoded by the target mRNA is reduced

Which of the following describes plant virus infections?

They are spread via the plasmodesmata

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

continuous transcription of the operon's genes

In many ways, the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes. Therefore, which of the following would you expect of the genes of the bacteriophage?

control of more than one gene in an operon

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

copies of the herpesvirus genome permanently maintained in host nuclei

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One of her colleagues suggested she try increased methylation of C nucleotides in a mammalian system. Which of the following results would she most likely see?

inactivation of the selected genes

Which of the following characteristics, structures, or processes is common to both bacteria and viruses?

genetic material composed of nucleic acid

If you were to observe the activity of methylated DNA, you would expect it to

have turned off or slowed down the process of transcription

In the figure, at the arrow marked II, what enzyme(s) are being utilized?

host cell DNA polymerase

RNA viruses require their own supply of certain enzymes because

host cells lack enzymes that can replicate the viral genome

Antiviral drugs that have become useful are usually associated with which of the following properties?

interference with viral replication

Which of the following is a protein produced by a regulatory gene?

repressor

Emerging viruses arise by

the spread of existing viruses to new host species mutation of existing viruses the spread of existing viruses more widely within their host species

The tryptophan operon is a repressible operon that is

turned off whenever tryptophan is added to the growth medium

Which of the following is characteristic of the lytic cycle?

A large number of phages are released at a time

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

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

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely?

Beta galactosidase will not be produced

Since Watson and Crick described DNA in 1953, which of the following might best explain why the function of small RNAs is still being explained?

Changes in technology as well as our ability to determine how much of the DNA is expressed have now made this possible

Based on the table, which virus meets the Baltimore requirements for a retrovirus?

D Rnase, absence of genome as mRNA, presence of polymerase

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious If you already knew that the infectious agent was either bacterial or viral, which treatment would allow you to distinguish between these two possibilities?

III

Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your kidney cells

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. 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?

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

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

Viral genomes are usually similar to the genome of the host cell

You are given an experimental problem involving control of a gene's expression in the embryo of a particular species. One of your first questions is whether the gene's expression is controlled at the level of transcription or translation. Which of the following might best give you an answer?

You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same

Which of the following is most likely to have a small protein called ubiquitin attached to it?

a cyclin that usually acts in G1, now that the cell is in G2

In response to chemical signals, prokaryotes can do which of the following?

alter the level of production of various enzymes

A human pandemic is

an epidemic that extends around the world

In eukaryotes, general transcription factors

bind to other proteins or to a sequence element within the promoter called the TATA box

The role of a metabolite that controls a repressible operon is to

bind to the repressor protein and activate it

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see?

decreased chromatin condensation

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious If you already knew that the infectious agent was either a viroid or a prion, which treatment would allow you to distinguish between these two possibilities?

either I or IV

Genomic imprinting, DNA methylation, and histone acetylation are all examples of

epigenetic phenomena

A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Of the lines that express the transgene, one is transcribed but not translated. Which of the following is a likely explanation?

no AUG in any frame

At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. There was surprise expressed by many that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for most of the rest?

non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function

Transcription of the structural genes in an inducible operon

starts when the pathway's substrate is present

One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs?

targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease

The lactose operon is likely to be transcribed when

the cyclic AMP and lactose levels are both high within the cell