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?

Which of the following is the best description of a bacteriophage?

Which of the following is not a component of HIV?

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, PrP^C, a transmembrane protein whose function remains unclear. 

Infectious prions, PrP^Res, induce conformational changes in the existing PrP^C proteins according to the following reaction:

PrP^C  + PrP^Res  → PrP^Res + PrP^Res

The PrP^Res 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?

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

What molecule would you not expect to find in a retrovirus?

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?

What component is common for all viruses?

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?

Which of the following is not found in a virus?