A fourth type of restriction enzyme is identified that cleaves at precise locations like a type II enzyme, but it also occasionally makes mistakes and cuts elsewhere. Would this type of enzyme be a useful enzyme to use in molecular cloning?

Question

A.  Yes, because it cuts correctly sometimes.
B.  No, because it is a precise enzyme.
C.  No, because cutting mistakes could lead to incorrect cloning.
D.  Yes, because cutting mistakes don't matter in molecular cloning.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

  Gather Content
· What do you already know about restriction enzymes?

  Consider Possibilities
  · What other information is related to the question? Which information is most useful?
 
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.  No, because cutting mistakes could lead to incorrect cloning.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses restriction enzymes.
· What type of thinking is required?
        o This question is asking you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
· What key words does the question contain and what do they mean?
        o Restriction enzymes are enzymes that cut DNA at specific recognition sites.
        o Cleaving means cutting DNA.
        o Molecular cloning is the process of cutting and pasting pieces of DNA to make something new, and growing it in large quantity in bacteria.

  Gather Content
· What do you already know about restriction enzymes?
        o Restriction enzymes recognize a specific DNA sequence, ranging from 4 bases to 12 bases, and cleave the DNA at a specific base within this sequence.
        o The recognition sites for most type II enzymes are palindromes. The palindromic DNA sequence reads the same from 5¢ to 3¢ on one strand as it does on the complementary strand.
        o Given this kind of sequence, cutting the DNA at the same base on either strand produces staggered cuts that leaves “sticky ends,” or overhangs.
        o These cuts and overhangs are used to cut and paste together pieces of DNA to create new combinations.

  Consider Possibilities
  · What other information is related to the question? Which information is most useful?
        o Would a messy enzyme be useful in molecular cloning? Not likely, because its behavior would be unpredictable.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o In molecular cloning, precision is paramount. If the enzyme cut in the wrong spot, the resulting product would be wrong.
        o It would be much more difficult to piece together the desired sequence if the enzyme was unpredictable.

  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 asked whether a messy restriction enzyme would be a problem.
        o The question required you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
        o Did you recognize that having enzymes that cut reliably in precise places is crucial for successful cloning?