A mutation in the gene encoding the integrase enzyme renders the protein non-functional. How would this affect-the HIV infection cycle?

Question

A.  The gp120 glycoprotein would not be able to bind the CCR5 receptor.
B.  Reverse transcription would not be possible. 
C.  The viral DNA would not be able to integrate the viral genome into a chromosome.
D.  Cutting and assembling the capsid would be halted. 

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
 
Gather Content
· What do you already know about the HIV infection cycle?
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  The viral DNA would not be able to integrate the viral genome into a chromosome.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses the HIV infection cycle.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.
 
Gather Content
· What do you already know about the HIV infection cycle?
        o The HIV infection cycle has multiple steps, using several viral-encoded enzymes.
        o The gp120 protein binds to the CD4 receptor and then the CCR5 receptor, to dock and fuse into the cell.
        o Reverse transcriptase creates a doublestranded DNA copy of the viral RNA genome.
        o Integrase allows the viral DNA to merge into a host cell chromosome.
        o The genome is transcribed, translated, processed by proteases and then new viruses are assembled and released.
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o If integrase was mutated, would the gp120 glycoprotein be unable to bind the CCR5 receptor? No, gp120 can interact with CCR5 directly after undergoing a conformational change.
        o If integrase was mutated, would reverse transcription be impossible? No, that is the job of reverse transcriptase.
        o If integrase was mutated, would cutting and assembling the capsid be halted? No, that is the job of protease.
        o If integrase was mutated, would the viral DNA be unable to incorporate into the host cell chromosome? Yes. Integrase is necessary to integrate into the viral DNA into the host cell chromosome.
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that the integrase enzyme is necessary to integrate the viral DNA into the host cell genome?