Although there are about 30,000 genes in the human body, approximately 120,000 proteins can be created in the body. This is caused by __________.

What is the purpose of the poly A tail attached to the primary transcript prior to translation?

What is a common modification that occurs on histone tails to modulate gene expression?

Which of the following experimental methods cannot be used to measure the relative abundance of a particular mRNA?

Three isoforms of a particular protein (variants A, B, and C) are expressed. In the following diagram, exons are indicating by boxes, introns by the black lines, and splice junctions by blue lines. Assume each exon is greater than 500 bp in length (figure not drawn to scale).

In the absence of available antibodies for Western blotting, how would one experimentally determine if variant C was expressed in HeLa cells?

Which of the following cell organelles is responsible for making proteins?

Protein is translated from __________ transcripts.

Which intermediates of the central dogma of molecular biology below are present in normal cellular replication, but apparently absent in the above model of prion replication?

I. mRNA

II. tRNA

III. Protein

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.

Which of the following findings would most strongly refute the protein-transmission hypothesis of prion propagation?

Cryptosporidium is a genus of gastrointestinal parasite that infects the intestinal epithelium of mammals. Cryptosporidium is water-borne, and is an apicomplexan parasite. This phylum also includes Plasmodium, Babesia, and Toxoplasma. 

Apicomplexans are unique due to their apicoplast, an apical organelle that helps penetrate mammalian epithelium. In the case of cryptosporidium, there is an interaction between the surface proteins of mammalian epithelial tissue and those of the apical portion of the cryptosporidium infective stage, or oocyst. A scientist is conducting an experiment to test the hypothesis that the oocyst secretes a peptide compound that neutralizes intestinal defense cells. These defense cells are resident in the intestinal epithelium, and defend the tissue by phagocytizing the oocysts. 

She sets up the following experiment:

As the neutralizing compound was believed to be secreted by the oocyst, the scientist collected oocysts onto growth media. The oocysts were grown among intestinal epithelial cells, and then the media was collected. The media was then added to another plate where Toxoplasma gondii was growing with intestinal epithelial cells. A second plate of Toxoplasma gondii was grown with the same type of intestinal epithelium, but no oocyst-sourced media was added.

The scientist in the passage develops an effective treatment for cryptosporidium infection. The treatment exploits a difference in the rRNA structure between cryptosporidium and its human hosts. In which organelle is this difference most likely to directly manifest?