Identify a sequence that is most likely to be recognized by a restriction enzyme.

Question

A.  CGATGC
B.  CCCTTT
C.  TGGCCA
D.  TCATCA

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.  TGGCCA

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses .
· 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.
· What key words does the question contain and what do they mean?
        o A restriction enzyme cleaves within DNA, only at particular sequences called restriction sites.

  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.

  Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o We have learned that restriction enzymes usually recognize sites that are palindromes – that is, the sequence reads the same from 5’ to 3’ on each strand.

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o The only sequence listed that is a palindrome is TGGCCA.
        o The double strand would read the same forwards and back:
        o 5’ TGGCCA 3’
        o 3’ ACCGGT 5’
   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 you to identify the most likely restriction enzyme recognition site.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that restriction sites are usually palindromes?