Table of Contents
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Jmol Tutorial

In this module:

Polymerization of Nucleotides
Base Pairing 1
Base Pairing 2
Complementary Sequences

Complementary Nucleotide Sequences

Because of the nature of complementary base pairing, if you know the sequence of one strand of DNA, you can predict the sequence of the strand that will pair with, or "complement" it.

Remember, when writing complementary DNA sequences, you need to write the sequence in the 5' to 3' direction. This usually involves reversing the sequence after writing it complementary to the one you are given.

Give the DNA sequence that will pair with the following stretches of DNA. Question 1 simulates the first step, finding the complementary sequence. Question 2 adds the second step, reversing the sequence to give the proper 5'-3' orientation. Question 3 combines these two steps without any hints on the orientation, i.e., it just gives and expects the sequences without explicitly giving the 5' and 3' ends.

1. 5'-TGC-3'

2. 5'-ATCCG-3'


3'-TGC-5' 5'-GCCAT-3'
3'-ACG-5' 5'-GCCTA-3'
3'-GCA-5' 5'-TAGGC-3'
3'-CGT-5' 5'-CGGAT-3'
Correct! You have paired A with T and G with C and given the correct 5' to 3' orientation.
Remember, A pairs with T and G pairs with C.
Remember to give the correct 5' to 3' orientation.

Complementary Sequences