If a mutation produced helicase that was unable to hydrolyze ATP, DNA replication would be

Question

A.  stopped.
B.  speeded up.
C.  unaffected.
D.  more prone to errors.

Clarify Question
· What is the key concept addressed by the question?
  · What type of thinking is required?
  · What key words does the question contain?

Gather Content
  · What do you already know about the function of helicase?

  Consider Possibilities
  · Consider the different answer options. Which can you rule out?

  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

A.  stopped.

Clarify Question
· What is the key concept addressed by the question?
    o This question addresses the function of helicase.
  · What type of thinking is required?
    o You need to Analyze the information given, using logic, to dissect the problem and determine the answer.
  · What key words does the question contain?
    o Helicase is the enzyme that unwinds DNA during DNA replication (the process of making new copies of DNA). Hydrolyzing ATP means breaking ATP down into ADP and a phosphate. Hydrolysis means breaking (lysis) using water (hydro).

Gather Content
  · What do you already know about the function of helicase?
    o Helicase unwinds the double helix of DNA at the replication fork. The strands have to be separated in order to be copied.
    o Helicase uses ATP as a source of energy to separate the strands, which are more stable bound together.

  Consider Possibilities
  · Consider the different answer options. Which can you rule out?
    o We know that helicase requires ATP. So a mutation that prevented hydrolysis of ATP would mean helicase couldn’t get energy to do its job.
    o We also know that helicase is an important part of the replication machinery, so having it “broken” would definitely interfere with DNA replication.
    o So we can rule out the answer that says DNA replication would be unaffected.

  Choose Answer   · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
    o So if helicase was “broken”, what would result? The DNA would stay double-stranded and wound together.
    o If DNA stayed double stranded, the whole replication fork would stop and could not continue.
    o It would not speed up or even continue with errors, because the DNA polymerase would not have access to the template strand for copying.

  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 This question required you to Analyze the information given, using logic, to dissect theproblem and determine the answer.
    o Did you remember that helicase acts to unwind the double-stranded DNA?
    o Did you recognize that helicase must hydrolyze ATP to have energy to drive the unwinding?