m42,43 - ebnalfady

[ArchivalUser]

42. The σ factor found in many bacteria is best described as a
a. Subunit of RNA polymerase responsible for the specificity of the initiation of transcription of RNA from DNA
b. Subunit of DNA polymerase that allows for synthesis in both 5' to 3' and 3' to 5' directions
c. Subunit of the 50S ribosome that catalyzes peptide bond synthesis
d. Subunit of the 30S ribosome to which mRNA binds
e. Factor that forms the bridge between the 30S and 50S particles constituting the 70S ribosome

43. An immigrant from eastern Europe is rushed into the emergency room with nausea, vomiting, diarrhea, and abdominal pain. His family indicates he has eaten wild mushrooms. They have brought a bag of fresh, uncooked mushrooms from a batch he had not yet prepared. You note the presence of Amanita phalloides, the death-cap mushroom. A liver biopsy indicates mas¬sive hepatic necrosis. Care is supportive. A major toxin of the death-cap mushroom is the hepatotoxic octapeptide α-amanitin, which inhibits
a. DNA primase
b. RNA nuclease
c. DNA ligase
d. RNA polymerase
e. RNA/DNA endonuclease

[ArchivalUser]

42.....not sure D
43...DDDDD

[ArchivalUser]

43 D 42a

[ArchivalUser]

42 AAA
43 DD

[ArchivalUser]

42.
The answer is a
. factor is a bacterial protein that can associate with and become a subunit of bacterial RNA polymerase. . factor confers


specificity of initiation on the core enzyme. In the presence of . factor, RNA polymerase chooses the correct strand of duplex DNA for transcrip­tion and initiates transcription at the appropriate promoter region. In some bacteria, such as Bacillus subtilis, a specific . factor is synthesized to change transcriptional selectivity and effect cellular changes like sporulation.
43.
The answer is d.
The deadly mushroom A. phalloides has several toxins. A major toxin is .-amanitin, an octapeptide that inhibits mRNA synthesis by very tightly binding RNA polymerase II (DNA-dependent RNA polymerase). As little as one of the mushrooms (know as the death-cap, death-cup, or avenging angel) delivers a lethal dose of about 10 mg .-amanitin. Severe, irreversible liver damage occurs quickly, leading to death. At higher concentrations, the toxin can inhibit RNA polymerase III and tRNA synthesis. Polymerase I is unaffected. Since .-amanitin is effec­tive at concentrations of 10.9 to 10.8 M, it has been useful as a research tool for studying RNA polymerase function.