Question

1. The tail fibers of a bacteriophage are most useful during which of the following stages of the lytic replication cycle?                                                                                                                                                                                                                                                                      

A. entry                      

B. assembly                

C. synthesis              

D. attachment

2. Which of the following is a major difference between a lysogenic and a lytic cycle in bacteriophages?                                                                                                                                                                                     

A. The bacteriophage attaches to bacterial surface receptor proteins only in a lysogenic cycle                                                                                                                                                                                                             

B. Viral DNA is inserted into the bacterial cell only in a lytic cycle.                                                                                   

C. Only lytic cycles can be caused by DNA-containing bacteriophages.                                                                 

D. Viral DNA becomes a physical part of the bacterial chromosome only in a lysogenic cycle.

3. The following statements is/are true of prions                                                                                                                                  

A. Readily inactivated by autoclaving at 121 ˚C                    

B. Contain DNA                                                                    

C. May cause Creutzfeldt Jakob disease                                 

D. May be readily cultured                                                

E. More than one answer         

Answer 1

1.D. The tail fibers are mostly required by the bacteriophages to get attached to the host cell. The proteins present get attached to the receptors on the host cell and leads to a large confirmational change in the tail by which the bacteriophage enters the host cell.

2.D. In lytic cycle the viral DNA doesn't get integrated into the bacterial chromosome but replicates independently and lyse the host cell while in lysogenic cycle the DNA gets integrated and replicates with the host DNA and gets passed into daughter cells.

3.E. Prions are infectious particles which are formed from misfolded proteins which can make other normal proteins infectious. A,B and D are correct.