Common structural elements in proteins such as α-helices or β-sheets are characterized by uniformly repeating, energetically favorable main chain conformations which additionally exhibit a completely saturated hydrogen-bonding network of the main chain NH and CO groups. Although polyproline or polyglycine type II helices (PPII or PGII ) are frequently found in proteins, they are not considered as equivalent secondary structure elements. Which of the following statements are correct about PP and PGs.

A. PGII -like helices form hexagonal bundles which appear to fulfill the criterion of a (largely) saturated hydrogen-bonding network of the main-chain groups

B. main chain NH and CO groups of the central PGII -helix are saturated by either intra- or intermolecular hydrogen-bonds, resulting in a self-contained hydrogen-bonding network

C. The formation of the right-handed PPI helix is possible only with proline residues because of the required cis conformation. 

D. PPII helices seem to be stabilized by main chain-water hydrogen bonds (in the absence of main chain- main chain H-bonds), and tend to have a regular pattern of hydrogen bonds with water. After this, it is not surprising, that PPII helices are found mostly on the protein surface.

#Question id: 5249

#Part-A Aptitude & General Biotechnology

What is the best explanation for why Bernard Davis didn't observe generalized transduction in his U tube experiments?

#Question id: 5250

#Part-A Aptitude & General Biotechnology

A researcher would like to map the location of galE and trpA genes in a new species of bacterium that appears to be closely related to E. coli. He decides to use cotransduction, and generatesnappropriate donor and recipient strains. He is disappointed when cotransduction is not seen in his experiement. What is the most reasonable explanation for this situation?

#Question id: 5251

#Part-A Aptitude & General Biotechnology

What do transduction, transformation, and conjugation have in common?

#Question id: 5252

#Part-A Aptitude & General Biotechnology

Which type(s) of genetic transfer lead to incorporation of new DNA into the bacterial chromosome?

I. Conjugation mediated by F factor

II. Hfr mediated conjugation

III. Transduction

IV. Transformation

#Question id: 5253

#Part-A Aptitude & General Biotechnology

In a hypothetical situation, the genes for sex pilus construction and for tetracycline resistance are located together on the same plasmid within a particular bacterium. If this bacterium readily performs conjugation involving a copy of this plasmid, then the resultshould be

#Question id: 5255

#Part-A Aptitude & General Biotechnology

Which of the following is a structure that permits conjugation to occur?