Experts in deer ecology generally agree that population sizes of deer that live in temperate climates are limited by winter snow. The deer congregate in ?yarding? areas under evergreen trees because venturing out to feed in winter is energetically too expensive when snowfall depths accumulate to above 40 cm. Deer often stay yarded until the spring thaw. Snow depth over 40 inches for more than 60 days results in high mortality due to starvation.  This observation best illustrates which of the following principles about factors that limit distribution of organisms?

#Question id: 4266

#Unit 3. Fundamental Processes

48S pre initiation complex is

#Question id: 4267

#Unit 3. Fundamental Processes

The 3D structure of the complete Escherichia coli ribosome with bound mRNA and tRNAs revealed that the very amino terminus of one protein (L27) does reach into the active site. This finding suggested a role for this protein in catalysis. To test this possibility, the nine amino acids at the L27 amino terminus that were in close proximity to the active site were eliminated by mutation. The following possible outcomes were found to be correct as

A. The resulting cells produced ribosomes with reduced but detectable peptidyl transferase activity

B. Region of the L27 protein contributes to peptidyl transferase activity

C. The mutant ribosomes, didn’t synthesised wildtype levels of cells

D. Vast majority of this increase in peptide bond formation is retained, even without the presence of L27 in the active site

E. The most likely role for L27 is to correctly position one or more of the RNA components of the active site

#Question id: 4268

#Unit 3. Fundamental Processes

23S rRNA catalyze peptide-bond formation as

A. base pairing between the 23S rRNA and the CCA ends of the tRNAs

B. A- and P-sites positions the a-amino group of the aminoacyl-tRNA to attack the carbonyl group of the growing polypeptide attached to the peptidyl-tRNA

C. Entropic catalysis is involved

#Question id: 4269

#Unit 3. Fundamental Processes

The kinase P-TEFb

A. Is recruited to polymerase by transcriptional activators

B. Phosphorylates the serine 2&5 of the CTD repeats for elongation

C. Phosphorylates SPT5 and TAT-SF1

#Question id: 4270

#Unit 3. Fundamental Processes

RNA helicase contains characteristic

#Question id: 4271

#Unit 3. Fundamental Processes

To participate successfully in the peptidyl transferase reaction, the tRNA must rotate into the peptidyl transferase center of the large subunit in a process called as