Viruses - MCAT Biology
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A mad scientist is working with a rare retrovirus under the hood, when he accidentally spills the viral sample over three live tissue cultures. Assuming the cultures were composed of stem cells, epithelial cells, and muscle cells, in which sample would the mad scientist expect to find the lowest viral titer?
A mad scientist is working with a rare retrovirus under the hood, when he accidentally spills the viral sample over three live tissue cultures. Assuming the cultures were composed of stem cells, epithelial cells, and muscle cells, in which sample would the mad scientist expect to find the lowest viral titer?
This question requires knowledge of two concepts: first, that retroviruses integrate their own genetic material into the host and are propagated during normal cell division; second, that some cell types do not continue to divide once they have reached maturity (muscle and nerve).
This question requires knowledge of two concepts: first, that retroviruses integrate their own genetic material into the host and are propagated during normal cell division; second, that some cell types do not continue to divide once they have reached maturity (muscle and nerve).
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Which of the following is the best description of a bacteriophage?
Which of the following is the best description of a bacteriophage?
A bacteriophage is a virus that infects bacteria. They are not considered living (becuase they cannot replicate on their own) organisms, nor are they techincally considered non-living organisms. They are called obligate intracellular organisms, because they are parasites (kill the cell) that require a host in order to replicate.
A bacteriophage is a virus that infects bacteria. They are not considered living (becuase they cannot replicate on their own) organisms, nor are they techincally considered non-living organisms. They are called obligate intracellular organisms, because they are parasites (kill the cell) that require a host in order to replicate.
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Which of the following is not a component of HIV?
Which of the following is not a component of HIV?
HIV is a retrovirus, meaning that it contains RNA as its genetic material, and thus reverse transcriptase to code for DNA from the RNA template. It also has a protein coat, and must use proteases in order to degrade the host cell membrane to inject its RNA. It does not, however, have ribosomes. It will eventually use the host ribosomes to translate its own genetic material.
HIV is a retrovirus, meaning that it contains RNA as its genetic material, and thus reverse transcriptase to code for DNA from the RNA template. It also has a protein coat, and must use proteases in order to degrade the host cell membrane to inject its RNA. It does not, however, have ribosomes. It will eventually use the host ribosomes to translate its own genetic material.
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Prions are the suspected cause of a wide variety of neurodegenerative diseases in mammals. According to prevailing theory, prions are infectious particles made only of protein and found in high concentrations in the brains of infected animals. All mammals produce normal prion protein, PrPC, a transmembrane protein whose function remains unclear.
Infectious prions, PrPRes, induce conformational changes in the existing PrPC proteins according to the following reaction:
PrPC + PrPRes → PrPRes + PrPRes
The PrPRes is then suspected to accumulate in the nervous tissue of infected patients and cause disease. This model of transmission generates replicated proteins, but does so bypassing the standard model of the central dogma of molecular biology. Transcription and translation apparently do not play a role in this replication process.
This theory is a major departure from previously established biological dogma. A scientist decides to test the protein-only theory of prion propagation. He establishes his experiment as follows:
Homogenized brain matter of infected rabbits is injected into the brains of healthy rabbits, as per the following table:
Rabbit 1 and 2: injected with normal saline on days 1 and 2
The above trials serve as controls.
Rabbit 3 and 4: injected with homogenized brain matter on days 1 and 2
The above trials use unmodified brain matter.
Rabbit 5 and 6: injected with irradiated homogenized brain matter on days 1 and 2
The above trials use brain matter that has been irradiated to destroy nucleic acids in the homogenate.
Rabbit 7 and 8: injected with protein-free centrifuged homogenized brain matter on days 1 and 2
The above trials use brain matter that has been centrifuged to generate a protein-free homogenate and a protein-rich homogenate based on molecular weight.
Rabbit 9 and 10: injected with boiled homogenized brain matter on days 1 and 2
The above trials use brain matter that have been boiled to destroy any bacterial contaminants in the homogenate.
Some scientists argue that there must be a virus or bacterium that cause infectious diseases, and claim that there is likely a heretofore undiscovered microbe causing neurodegeneration that most scientists claim are caused by PrPRes. What is a key way for these scientists to distinguish viruses from bacteria?
Prions are the suspected cause of a wide variety of neurodegenerative diseases in mammals. According to prevailing theory, prions are infectious particles made only of protein and found in high concentrations in the brains of infected animals. All mammals produce normal prion protein, PrPC, a transmembrane protein whose function remains unclear.
Infectious prions, PrPRes, induce conformational changes in the existing PrPC proteins according to the following reaction:
PrPC + PrPRes → PrPRes + PrPRes
The PrPRes is then suspected to accumulate in the nervous tissue of infected patients and cause disease. This model of transmission generates replicated proteins, but does so bypassing the standard model of the central dogma of molecular biology. Transcription and translation apparently do not play a role in this replication process.
This theory is a major departure from previously established biological dogma. A scientist decides to test the protein-only theory of prion propagation. He establishes his experiment as follows:
Homogenized brain matter of infected rabbits is injected into the brains of healthy rabbits, as per the following table:
Rabbit 1 and 2: injected with normal saline on days 1 and 2
The above trials serve as controls.
Rabbit 3 and 4: injected with homogenized brain matter on days 1 and 2
The above trials use unmodified brain matter.
Rabbit 5 and 6: injected with irradiated homogenized brain matter on days 1 and 2
The above trials use brain matter that has been irradiated to destroy nucleic acids in the homogenate.
Rabbit 7 and 8: injected with protein-free centrifuged homogenized brain matter on days 1 and 2
The above trials use brain matter that has been centrifuged to generate a protein-free homogenate and a protein-rich homogenate based on molecular weight.
Rabbit 9 and 10: injected with boiled homogenized brain matter on days 1 and 2
The above trials use brain matter that have been boiled to destroy any bacterial contaminants in the homogenate.
Some scientists argue that there must be a virus or bacterium that cause infectious diseases, and claim that there is likely a heretofore undiscovered microbe causing neurodegeneration that most scientists claim are caused by PrPRes. What is a key way for these scientists to distinguish viruses from bacteria?
Bacteria have ribosomes to facilitate protein synthesis, but lack other membrane bound organelles such as nuclei, Golgi, or mitochondrion. Viruses lack all of these, including ribosomes.
Bacteria have ribosomes to facilitate protein synthesis, but lack other membrane bound organelles such as nuclei, Golgi, or mitochondrion. Viruses lack all of these, including ribosomes.
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Which of the following is not a described type of virus?
I. A virus containing double strand DNA
II. A virus containing single strand DNA
III. A virus containing single strand RNA and single strand DNA
IV. A virus containing single strand RNA
V. A virus containing double strand RNA
Which of the following is not a described type of virus?
I. A virus containing double strand DNA
II. A virus containing single strand DNA
III. A virus containing single strand RNA and single strand DNA
IV. A virus containing single strand RNA
V. A virus containing double strand RNA
The question addresses the Baltimore classification system for viral genetic information. Viruses contain some form of DNA or RNA, but never both.
The question addresses the Baltimore classification system for viral genetic information. Viruses contain some form of DNA or RNA, but never both.
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What molecule would you not expect to find in a retrovirus?
What molecule would you not expect to find in a retrovirus?
Retroviruses carry RNA and when they infect a host cell, they use their own reverse transciptase to made DNA from that RNA; therefore, within the virus, there are only the molecules that make up RNA. Uracil is used in RNA place of thymine, which can be found in DNA. Cytosine, guanine, and adenine can be found in both DNA and RNA.
Retroviruses carry RNA and when they infect a host cell, they use their own reverse transciptase to made DNA from that RNA; therefore, within the virus, there are only the molecules that make up RNA. Uracil is used in RNA place of thymine, which can be found in DNA. Cytosine, guanine, and adenine can be found in both DNA and RNA.
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Sexually transmitted diseases are a common problem among young people in the United States. One of the more common diseases is caused by the bacterium Neisseria gonorrhoeae, which leads to inflammation and purulent discharge in the male and female reproductive tracts.
The bacterium has a number of systems to evade host defenses. Upon infection, it uses pili to adhere to host epithelium. The bacterium also uses an enzyme, gonococcal sialyltransferase, to transfer a sialyic acid residue to a gonococcal surface lipooligosaccharide (LOS). A depiction of this can be seen in Figure 1. The sialyic acid residue mimics the protective capsule found on other bacterial species.
Once infection is established, Neisseria preferentially infects columnar epithelial cells in the female reproductive tract, and leads to a loss of cilia on these cells. Damage to the reproductive tract can result in pelvic inflammatory disease, which can complicate pregnancies later in the life of the woman.
Which of the following is true of Neisseria, but not true of a virus?
Sexually transmitted diseases are a common problem among young people in the United States. One of the more common diseases is caused by the bacterium Neisseria gonorrhoeae, which leads to inflammation and purulent discharge in the male and female reproductive tracts.
The bacterium has a number of systems to evade host defenses. Upon infection, it uses pili to adhere to host epithelium. The bacterium also uses an enzyme, gonococcal sialyltransferase, to transfer a sialyic acid residue to a gonococcal surface lipooligosaccharide (LOS). A depiction of this can be seen in Figure 1. The sialyic acid residue mimics the protective capsule found on other bacterial species.
Once infection is established, Neisseria preferentially infects columnar epithelial cells in the female reproductive tract, and leads to a loss of cilia on these cells. Damage to the reproductive tract can result in pelvic inflammatory disease, which can complicate pregnancies later in the life of the woman.
Which of the following is true of Neisseria, but not true of a virus?
Neisseria synthesizes proteins as a free living prokaryote. Viruses are generally dependent on host cellular machinery, and synthesize their proteins upon hijacking of a host ribosome.
Neisseria synthesizes proteins as a free living prokaryote. Viruses are generally dependent on host cellular machinery, and synthesize their proteins upon hijacking of a host ribosome.
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What component is common for all viruses?
What component is common for all viruses?
All viruses contain a protein coat (or capsule) that protects the genetic material (which can be either DNA or RNA). In some instances (such as herpes simplex), the virus can also contain an lipid envelope that serves as a membrane.
All viruses contain a protein coat (or capsule) that protects the genetic material (which can be either DNA or RNA). In some instances (such as herpes simplex), the virus can also contain an lipid envelope that serves as a membrane.
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In the crusade to create a vaccine for Poliomyelitis, Jonas Salk and Albert Sabin created two separate vaccines that proved to be successful in preventing Polio onset.
The Salk vaccine, which is given by standard injection, contained virus particles inactivated by an organic solvent. This method has the advantage of inactivating each of the three Polio strains with no bias.
Albert Sabin's vaccine, given by oral inoculation via sugar water, contained live virus particles that had been genetically attenuated. With this method, each of the three Polio strains acquired separate mutations that made them unable to infect the human host cells. Strain 2 in particular contained one single nucleotide polymorphism in the internal ribosomal entry site (IRES) that prevented successful viral replication.
Based on the passage above, what is the biggest disadvantage to Albert Sabin's vaccine?
In the crusade to create a vaccine for Poliomyelitis, Jonas Salk and Albert Sabin created two separate vaccines that proved to be successful in preventing Polio onset.
The Salk vaccine, which is given by standard injection, contained virus particles inactivated by an organic solvent. This method has the advantage of inactivating each of the three Polio strains with no bias.
Albert Sabin's vaccine, given by oral inoculation via sugar water, contained live virus particles that had been genetically attenuated. With this method, each of the three Polio strains acquired separate mutations that made them unable to infect the human host cells. Strain 2 in particular contained one single nucleotide polymorphism in the internal ribosomal entry site (IRES) that prevented successful viral replication.
Based on the passage above, what is the biggest disadvantage to Albert Sabin's vaccine?
Because Polio strain 2 only has a single nucleotide mutation, there is a much higher chance of the RNA dependent RNA polymerase (RDRP), which is highly error prone, spontaneously reverting the mutation and restoring virulence.
Poliovirus is actually very stable in sugar solutions, which eliminates the possibility that virus would be dead upon deliverance. Viruses are also incapable of synthesizing their genome without the aid of the host cell, so the sugar content of the inoculum solution would have no effect on viral infectivity.
Because Polio strain 2 only has a single nucleotide mutation, there is a much higher chance of the RNA dependent RNA polymerase (RDRP), which is highly error prone, spontaneously reverting the mutation and restoring virulence.
Poliovirus is actually very stable in sugar solutions, which eliminates the possibility that virus would be dead upon deliverance. Viruses are also incapable of synthesizing their genome without the aid of the host cell, so the sugar content of the inoculum solution would have no effect on viral infectivity.
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Viral genomic material can be comprised of which types of nucleic acids?
I. Single-stranded DNA
II. Double-stranded DNA
III. Single-stranded RNA
IV. Double-stranded RNA
Viral genomic material can be comprised of which types of nucleic acids?
I. Single-stranded DNA
II. Double-stranded DNA
III. Single-stranded RNA
IV. Double-stranded RNA
Different classes of viruses store genetic material in different forms.
Double-stranded RNA (dsRNA) viruses, single-stranded RNA (ssRNA) viruses, double-stranded DNA (dsDNA) viruses, and single-stranded DNA (ssDNA) viruses are all large classes of viral classification. Retroviruses can be classified as ssRNA viruses, but are often left in their own category.
Different classes of viruses store genetic material in different forms.
Double-stranded RNA (dsRNA) viruses, single-stranded RNA (ssRNA) viruses, double-stranded DNA (dsDNA) viruses, and single-stranded DNA (ssDNA) viruses are all large classes of viral classification. Retroviruses can be classified as ssRNA viruses, but are often left in their own category.
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Which of the following is not found in a virus?
Which of the following is not found in a virus?
Viruses use the hosts ribosomes to translate their genes, and do not possess their own organelles for replication. Viruses are made of a protein buffy coat with genetic material (DNA or RNA) inside.
Viruses use the hosts ribosomes to translate their genes, and do not possess their own organelles for replication. Viruses are made of a protein buffy coat with genetic material (DNA or RNA) inside.
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Which of the following is not a property of viruses?
Which of the following is not a property of viruses?
Viruses cannot reproduce and make copies of themselves without a host; however, they can survive on their own. Viruses can remain dormant in a non-biological environment before being transferred to a biological host.
All viruses carry some form of genetic material, either in the form of DNA or RNA, and have a protein coat to contain the genetic material. Bacteriophages are viruses that specifically target bacteria. By hijacking the cellular machinery of host cells, viruses are able to replicate, essentially becoming intracellular parasites.
Viruses cannot reproduce and make copies of themselves without a host; however, they can survive on their own. Viruses can remain dormant in a non-biological environment before being transferred to a biological host.
All viruses carry some form of genetic material, either in the form of DNA or RNA, and have a protein coat to contain the genetic material. Bacteriophages are viruses that specifically target bacteria. By hijacking the cellular machinery of host cells, viruses are able to replicate, essentially becoming intracellular parasites.
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Polio is a highly infectious disease caused by the polio virus, which can be a debilitating disease in the worst case scenarios. The first effective vaccine for treating polio was developed by Jonas Salk at the University of Pittsburgh in 1952.
Salk's vaccine consisted of inactivated (dead) virus, administered orally. Which of the following statements is true regarding vaccines containing inactivated virus?
Polio is a highly infectious disease caused by the polio virus, which can be a debilitating disease in the worst case scenarios. The first effective vaccine for treating polio was developed by Jonas Salk at the University of Pittsburgh in 1952.
Salk's vaccine consisted of inactivated (dead) virus, administered orally. Which of the following statements is true regarding vaccines containing inactivated virus?
The process of inactivating live viruses results in dead (noninfectious) virus. In terms of safety (if the virus is inactivated correctly), inactivated virus vaccines have no risk of inducing a viral infection from the contents of the vaccine. In terms of effectiveness of inducing protective immunity, inactivated virus vaccines are typically less effective than attenuated but live virus vaccines. Therefore, the induction of long-term protective immunity against the virus is questionable. Inactivated virus vaccines normally require larger doses, multiple doses, and adjuvants to be effective.
The process of inactivating live viruses results in dead (noninfectious) virus. In terms of safety (if the virus is inactivated correctly), inactivated virus vaccines have no risk of inducing a viral infection from the contents of the vaccine. In terms of effectiveness of inducing protective immunity, inactivated virus vaccines are typically less effective than attenuated but live virus vaccines. Therefore, the induction of long-term protective immunity against the virus is questionable. Inactivated virus vaccines normally require larger doses, multiple doses, and adjuvants to be effective.
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