Which of the following DNA sequences is complementary to 5' ATGGTCAGT 3'?

Question

A.  5' ATGGTCAGT 3'
B.  5' TGACTGGTA 3'
C.  5' TACCAGTCA 3'
D.  5' ACTGACCAT 3'

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 base-pairing?

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

D.  5' ACTGACCAT 3'

Clarify Question
· What is the key concept addressed by the question?
    o This question addresses base-pairing.
· 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 A DNA sequence has a direction, which is referred to as 5’ to 3’, or 3’ to 5’. These refer to the carbons on the sugar molecule which connect between the phosphates in the backbone. The complementary sequence is the sequence of its opposite strand.

Gather Content
  · What do you already know about base-pairing?
    o Base-pairing is the interaction that connects the two strands of a DNA molecule.
    o A pairs with T, and G pairs with C.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
    o We have learned that the DNA strands are antiparallel. That means that one strand runs 5’ to 3’, and the other runs 3’ to 5’.
    o We can write the DNA either way, as long as we clearly note the direction. So 3’ ATCG 5’ is the same exact sequence as 5’ GCTA 3’.
    o Note that all the answer options are written to begin with 5’, just like the original sequence. So to match them, we should read from the 3’ end.
   Choose Answer
  · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
    o Starting at the 5’ of the original sequence, we can deduce the complementary sequence.
    o The original strand starts with 5’, so it’s complement begins at the 3’ end.
    o The original strand is 5' ATGGTCAGT 3'.
    o We know that A base pairs with T, and vice versa, and G base pairs with C, and vice versa.
    o So the complement of the original strand is 3’ TACCAGTCA 5’.
    o BUT, note that all the answer options are written from 5’ to 3’. So we need to flip our notation like so: 5’ ACTGACCAT 3’.

  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 A binds with T, and G binds with C?
    o Did you recognize that the two DNA strands are antiparallel?
    o Did you recognize that all the answer options were written from 5’ to 3’?