Ch 18

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lets suppose a bacterial strain divides every 30 minutes. if a single cell is placed on a plate, how many cells will be in the colony after 16 hours?

16 hours is the same as 32 doubling so 2^32+ 4,294,967,296( the actual number would be much less because the cells would deplete the growth media and grow more slowly than the maximal rate.)

how many nucleoid regions are in the bacterial cell to the far right

3

Bacterial vs. Eukaryotic Chromosomes Bacterial chromosomes and eukaryotic chromosomes have some key differences. Please check all of the following statements that are true of bacterial chromosomes: Bacterial species contain mostly linear chromosomes. Bacterial species contain mostly circular chromosomes. Bacterial chromosomes typically have 1,000-2,000 nucleotides. Bacterial species usually contain one type of chromosome, but may contain more than one copy. Multiple origins of replication are required to initiate DNA replication. The bacterial chromosome(s) are packaged into a nucleus. Bacterial chromosomes typically contain a few thousand genes.

Bacterial species contain mostly circular chromosomes. Bacterial species usually contain one type of chromosome, but may contain more than one copy Bacterial chromosomes typically contain a few thousand genes.

if the donor cell has only one F factor how the donor and recipient cell both contain one f factor following the transfer of an f factor during conjugation.

During conjugation, only one strand of the DNA from an F factor is transferred from the donor to the recipient cell. the single-stranded DNa in both cells is then used as a template to create double stranded F factor DNa in both cells.

Difference between enveloped virus and phage How is an enveloped virus structurally different from a phage, like T4? An enveloped virus has a protein capsid, but a phage lacks a protein capsid An enveloped virus has DNA as its genetic material, but a phage has RNA as its genetic material The entire enveloped virus enter the cell by fusing with the plasma membrane, and phage inject their DNA into its host cell leaving its 'body' outside the cell Enveloped virus possess an additional membrane around their protein capsid, phage do not possess a membrane. All of these are TRUE

Enveloped virus possess an additional membrane around their protein capsid, phage do not possess a membrane.

Process releasing virus What is another way to describe the process by which an enveloped virus is released by the host cell? Exocytosis Vesicular transport Secretion Excretion Facilitated diffusion

Exocytosis

Info to make an enveloped virus From what genome does the information come that produces an enveloped virus? Solely from the viral genome Solely from the host cell genome From infectious, transmissible proteins From both the host cell and the viral genome From the host cell genome, the viral genome, and from infectious, transmissible proteins

From both the host cell and the viral genome

how did the phenomenon of transformation allow researchers to demonstrate that DNA is the genetic material ?

Griffiths was abel to show that gentic material was transferred to tyope R bacteria, which converted them to type S. This occurred vis transformation. Later, Avery, macleod and McCarty determined that DNA was the material that was being transferred.

Origin of Viruses Which came first - viruses or living cells? Many biologists have argued that living cells existed before viruses evolved and use the existence of plasmids to support the argument. What property of plasmids indicates they may have been precursors to the first viruses? Plasmids are composed of RNA and it is believed that the first viruses had an RNA genome. Plasmids are small and replicate independently of chromosomal DNA. Plasmids that have been characterized today have capsid genes. A, B, and C are all correct

Plasmids are small and replicate independently of chromosomal DNA

How are retrovirus different? Other than the presence of RNA vs. DNA, how is a retrovirus different from other viruses? Retrovirus incorporate DNA into the host cell's genome Retrovirus make RNA transcripts of their own genome using the host cell's enzymes. Retrovirus carry an enzyme within the virion. Retrovirus do not kill their host cells Retrovirus can only infect animals, not plants or prokaryotes

Retrovirus carry an enzyme within the virion.

Characteristics of HIV and AIDS Treatment Which of the following characteristics of human immunodeficiency virus (HIV) makes the development of effective treatments very difficult? HIV is spread via sexual contact and blood transfusions with infected blood Upon infection by HIV, host cells are unable to be penetrated by any other foreign substance Reverse transcriptase does not have proofreading capabilities, thus more mistakes are made resulting in a greater rate of mutation HIV is constantly encapsulated by a protective proteinaceous coat that protects it from anti-viral drugs None, HIV routinely responds to a wide array of anti-viral drug therapies

Reverse transcriptase does not have proofreading capabilities, thus more mistakes are made resulting in a greater rate of mutation

Mechanism of Prion Transmission A scrapie prion invades a neuron of a host organism. Proteins that exist in a disease causing conformation are designated PrPSc and a normal conformation of this same protein is designated PrPC. Once the PrPSc enters the cell, which of the following is most likely to occur? The PrPSc protein will secrete newly synthesized proteins that will cause the host to replicate the prion genome, allowing further propagation and spread of the infection. The PrPSc protein will bind to a PrPC protein, converting the normal protein to the PrPSc conformation, spreading the infection and over time, forming neurodegenerative fibrils. The PrPSc protein enters the cell and does not affect normal conformations of the normal protein (PrPC), but accumulates over time, forming neurodegenerative fibrils. The PrPSc protein aggregates to form transport channels in the membrane, allowing more PrPSc proteins to enter the cell, leading to the formation of neurodegenerative fibrils. The PrPSc protein binds to ion-gated sodium channels and prevents them from opening, preventing the neuron from initiating an action potential.

The PrPSc protein will bind to a PrPC protein, converting the normal protein to the PrPSc conformation, spreading the infection and over time, forming neurodegenerative fibrils.

What does PrPc alter? When PrPsc converts PrPc, what is being altered? The DNA sequence of the gene that codes for PrPc The DNA sequence of the gene that codes for PrPsc The primary protein structure of PrPc The secondary protein structure of PrPc The secondary and tertiary protein structure of PrPc

The secondary and tertiary protein structure of PrPc

What's the next step? This animation ends with a virus entering a host cell and its protein capsid degrading and releasing nucleic acid into the cell. What will occur next if this virus exhibits a lysogenic life cycle? The virus will destroy the host's DNA. The virus will use the host's translation machinery to make viral proteins. The viral DNA will be incorporated into the host's DNA. The host cell will lyse. The virus will use the bacteria to make many copies of its genome.

The viral DNA will be incorporated into the host's DNA.

Which statement is TRUE Which of the following statements about the viral envelope is TRUE? The membrane of the viral envelope arises from transcription of viral DNA. The viral envelope is composed solely of components produced by the host cell's genome. The viral envelope contains some components that are from the host cell's genome and some from the viral genome. The membrane of the viral envelope is formed by engulfing the viral capsid in a vesicle.. None of these statements are TRUE

The viral envelope contains some components that are from the host cell's genome and some from the viral genome.

Which statement is TRUE Which of the following statements about the viral envelope is TRUE? The membrane of the viral envelope arises from transcription of viral DNA. The viral envelope is composed solely of components produced by the host cell's genome. The viral envelope contains some components that are from the host cell's genome and some from the viral genome. The membrane of the viral envelope is formed by engulfing the viral capsid in a vesicle.. None of these statements are TRUE.

The viral envelope contains some components that are from the host cell's genome and some from the viral genome.

Viral host recognition How does an enveloped virus recognize a suitable host cell? The virus recognizes pheromones secreted by the host. The virus can only incorporate its DNA into a suitable host's genome. The virus recognizes cytoskeletal elements that are associated with the host's plasma membrane. The virus recognizes cell surface receptors that are embedded in the host's plasma membrane. There is an innate attraction between an enveloped virus and its suitable host.

The virus recognizes cell surface receptors that are embedded in the host's plasma membrane.

Mutated reverse transcriptase If the reverse transcriptase enzyme carried by a retrovirus was mutated and nonfunctional, how would the virus be effected? The virus would not be able to recognize and attach to a host cell. The virus would not be able to enter the host cell. The virus would not be able to incorporate its RNA into the host's genome. The virus would not be able to produce DNA to incorporate into the host's genome. The virus would not be able to use the host to produce new viral proteins.

The virus would not be able to produce DNA to incorporate into the host's genome.

Prion reproduction How do prions 'reproduce?' They use the transcriptional and translational enzymes present in the host cell to reproduce themselves. They reproduce by binary fission. They reproduce by meiosis and syngamy. They reproduce by converting healthy proteins into infectious prions. All of these are TRUE.

They reproduce by converting healthy proteins into infectious prions

how is a nucleoid different from a nucleus found in a eukaryotic cell?

a nucleoid is not a membrane bound organelle. it is simply a region where a bacterial chromosome is found . a cell nucleus in a eukaryotic cell has an envelope with a double membrane,

gentic diversity is maintainted in bacterial populations by all of the following except a.binary fusion b.mutation c. transformation d.transduction e. conjunction

a.binary fusion

secondary structural motifs Based on the prion proteins illustrated in the animation, how is the secondary protein structure changed when a normal protein (PrPc) is changed into an infectious protein (PrPsc)? secondary structure is completely lost alpha helices are converted into beta pleated sheets beta pleated sheets are converted into alpha helices additional alpha helices are added to the protein additional beta pleated sheets are added to the protein

alpha helices are converted into beta pleated sheets

Viral spikes Viral spikes attach non-specifically to host cell receptors. attach specifically to host cell receptors. are made of carbohydrate. are present in all viruses.

attach specifically to host cell receptors.

a bacterial cell can donate DNA during conjugation when it a.produces competent factors b. contains an F factor c. is virulent d. has been infected by a bacteriophage. e. all of the above.

b. contains an F factor

HIV retrovirus has a high mutation rate because a. the DNA of the viral genome is less stable than other viral genomes. b. the viral enzyme reverse transcriptase has a high likelihood of making replication errors. c. the viral genome is altered every time it is incorporated into the host genome. d. antibodies produced by the host cell mutate the viral genome whe infection occurs. e. all of the above.

b. the viral enzyme reverse transcriptase has a high likelihood of making replication errors.

describe the similarities and differences between bacterial chromosomes and a plasmid.

bacterial chromosomes and plasmids are similar in that they typically contain circular DNA molecules . However bacterial chromosomes are usually much longer than plasmids and carry many more genes. Also, bacterial chromosomes tend to be more compacted due to the formation of loop domains and supercoiling.

The viral capsid The viral capsid engulfs the viral spikes. surrounds the viral matrix protein. becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.

becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.

The viral capsid The viral capsid engulfs the viral spikes. surrounds the viral matrix protein. becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded. is dissolved.

becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.

The normal prion protein is The normal prion protein is bound to the ribosomes of neurons. bound to the cell membrane of neurons. found in the nucleus of neurons. found in the mitochondria of neurons. found in the synapse between neurons.

bound to the cell membrane of neurons.

Enveloped viruses are usually released from ... Enveloped viruses are usually released from the host cell by budding. lysis of the host cell. endocytosis. phagocytosis.

budding.

A harmless PrP is converted into the infecti... A harmless PrP is converted into the infective PrP only as a result of a mutation in the normal gene. by a virus which binds to the normal protein and causes it to become misfolded. by an abnormal PrP which binds to the normal protein and causes it to become misfolded. by enzymes that break off parts of the harmless protein. by interaction of a PrP from one species with that of a second species.

by an abnormal PrP which binds to the normal protein and causes it to become misfolded.

How does someone contract a prion disease?

by either eating an animal with the diease, they get the abnormal protein

the___ is the protein coat of a virus that surrounds the genetic material a. host b. prion. c. capsid d. viroid e. capsule

c. capsid

a bacterial species that becomes resistant to certain antibiotics may have acquired the resistance genes from another bacterial species. the phenomenon of acquiring genes from another organism without the offspring of that organism is known as. a. hybridization b. intergration c. horizontal gene transfer d. vertical gene transfer e. competence.

c. horizontal gene transfer

during viral infection, attachment is usually specific to a particular cell type because a. the virus is attracted to the appropriate host cells by proteins secreted into the extracellular fluid. b. the virus recognizes and binds to specific molecules in the cytoplasm of the host cell c. the virus recognizes and binds to specific molecules on the surface of the host cell d. the host cell produces channel proteins that provide passageways for viruses to enter the cytoplasm. e. the viruses relases specific proteins that make holes in the membrane large enough for the virus to enter.

c. the virus recognizes and binds to specific molecules on the surface of the host cell

Bacterial cells divide by a process known as a.mitosis b. cytokinesis c. meiosis d. binary fission e. glycolysis

d. binary fission

gene transfer in which a bacterial cell takes up bacterial DNA from the enviroment is also called a. conjugation b. Binary fission c.asexual reproduction d. transformation e. transduction.

d. transformation

among the viruses identified, the charateristics of their genomes show many varriations, which of the following does not describe a typical characteristic of viral genomes? a. the genetic material may be RNA or DNA b. the nucleic acid may ne single stranded or double stranded. c. the genome may carry just a few genes or several dozen. d. the number of copies of the geome may vary. e. all of the above describe typical variation on viral genomes.

e. all of the above describe typical variation on viral genomes.

a____ is an infectious agent composed solely of RNA, whereas a ___ is an infectious agent composed solely of protein. a. retrovirus, bacteriophage b. viroid, virus c. prion , virus d. retrovirus, prion e. viroid , prion

e. viroid , prion

AIDS is such a devastating disease because ________ cells are destroyed, leaving the _______ ... AIDS is such a devastating disease because ________ cells are destroyed, leaving the _______ system vulnerable and the body susceptible to foreign, pathogenic invaders. neutrophils/circulatory helper T/immune neuron/nervous platelet/circulatory red blood/muscular

helper T/immune

In viral entry by endocytosis In viral entry by endocytosis host plasma membrane surrounds whole virion and forms a vesicle. host plasma membrane surrounds only viral protein coat and forms a vesicle. host plasma membrane surrounds only viral nucleic acid and forms a vesicle. host spikes fuse with host plasma membrane.

host plasma membrane surrounds whole virion and forms a vesicle

Which of the following diseases is(are) caus... Which of the following diseases is(are) caused by prions? mad cow disease Creutzfeldt-Jacob disease in humans scrapie disease in sheep mad cow disease and Creutzfeldt-Jacob disease in humans mad cow disease, Creutzfeldt-Jacob disease in humans, and scrapie disease in sheep

mad cow disease, Creutzfeldt-Jacob disease in humans, and scrapie disease in sheep

If the DNA of the provirus is transcribed If the DNA of the provirus is transcribed several single mRNA strands are produced. a plasmid is made. the provirus detaches and becomes lytic. one long polygenic mRNA is produced.

one long polygenic mRNA is produced.

The provirus state exists when The provirus state exists when double-stranded viral DNA is integrated into host cell chromosome. single-stranded viral RNA is integrated into host cell chromosome. double-stranded viral RNA is integrated into host cell chromosome. single-stranded RNA is present as a plasmid in the host cell. double-stranded DNA is present as a plasmid in the host cell.

single-stranded viral RNA is integrated into host cell chromosome.

from the perspective of the virus what are the primary advantages of the lytic and lysogenic cycles?

the advantages of the lytic cycle is that a viruss can make many copies of itself and proliferates.However sometimes the growth conditions may not be favorable to make new viruses. thaadvantage of the lysogentic cycle is that the virus can remain latent until conditions become favorable to make new viruses.

After the virus nucleocapsid is released fro... After the virus nucleocapsid is released from the vesicle into the host cell cytoplasm the viral nucleic acid is destroyed. it remains intact. the capsid protein is removed. the capsid protein becomes thicker.

the capsid protein is removed.

describe how the loop domains are held in place

the loop domains are held in place by proteins that bind to the DNA at the bases of the loops . the proteins also bind to each other.

Provirus stage When a provirus is incorporated into the host's genome, and no virions are being produced, this is known as the lytic phase the provirus phase the lysogenic phase the virulent phase the infectious phase

the lysogenic phase

Is transduction a normal part of the phage life cycle?

transduction is not a normal part of the phage life cycle. it is a mistake in which a piece of the bacteria chromosome is packaged into a phage coat and is then transferred to another bacterial cell.

Retroviruses have How can the genetic information of retroviruses be characterized? one copy of single-stranded RNA. two copies of single-stranded RNA. one copy of double-stranded RNA. two copies of single-stranded DNA.

two copies of single-stranded RNA.

how does the release if HIV resemble exocytosis?

viral relase occurs as budding process in which a membrane vesicle is formed that surrounds te capsid. similarly exocytosis involves the formation of a membrane vesicle that encloses some type of cargo.

The first event to occur is The first event to occur is inside of the host cell membrane becomes coated with viral matrix protein. viral capsid becomes enclosed by cell membrane. inside of host cell membrane becomes coated with capsid. viral spike proteins are inserted into host cell membrane.

viral spike proteins are inserted into host cell membrane.

what features vary among different types of viruses?

viruses vary with regard to their structure and their genomes.

would the reults have been different if the pore size was larger and allowed the passage of bacterial cells?

yes the two strains would have mixed together ,allowing them to conjugate. therefore,there would have been colonies on the plates.


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