Describe the major mRNA degradation pathway in E. coli
What will be an ideal response?
Ans: First, a pyrophosphate is removed from the 5? terminus, leaving a single phosphate. Next the endonuclease RNase E cleaves the mRNA near the 5? end, and the resulting fragment is degraded by PNPase from 3? to 5?. This cycle of cleavage and degradation continues as ribosomal clearance exposes 5? sections of the mRNA until it is completely degraded.
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Which of the following statements about nitrogenous waste excretion is correct?
A. Uric acid is less toxic than ammonia, but more energetically costly to produce. B. Ammonia is more toxic than urea, but requires less water for excretion. C. Urea is less toxic than uric acid, but more energetically costly to produce. D. Uric acid is less toxic than urea, but requires more water for excretion. E. Ammonia is less toxic than uric acid, but requires more water for excretion.
The term “respiration” in animals refers to the ____
a. movement of oxygen into an animal only b. movement of carbon dioxide out of an animal only c. movement of oxygen into an animal and the movement of carbon dioxide out of the animal d. binding of oxygen to hemoglobin molecules in the blood e. diffusion of oxygen across a cell membrane
A(n) ____ taxies foreign DNA into a host cell that can divide rapidly
a. primer b. intron c. DNA clone d. exon e. codon
Papillary muscles:
A. contract when the ventricles relax B. prevent the valves from closing during ventricular diastole C. are attached to the semi lunar valves via the chordae tendineae D. prevent the backflow of blood into the atria during ventricular systole E. prevent the backflow of blood into the ventricles from the aorta