G = Blue Blocks, C = Green Blocks , A = Red Blocks, T = Yellow Blocks

If you would like to know a little more about the specific details of DNA sequencing, read further.

You have already learned the LEGO® block lesson, where the simplified analogy that stacks of LEGO® blocks represent strands of DNA. Each LEGO® block in the previous lesson represented a DNA nucleotide G, A, T, or C by the color of the LEGO® block. These letters refered to guanine, adenine, thymine, and cytosine, which make up the DNA double helix. Each of the four colored LEGO® blocks represented a corresponding nucleotide as shown below.

In actual gene sequencing, G and C are complimentary and A and T are complimentary. This means that they must always be linked to each other when forming a double helix.

To form a double helix of DNA, you must have two strands of DNA. The two strands always have the complimentary letters across from each other.

When forming the double helix, the two strands of DNA spiral together to form the shape below. The complimentary letters, which are across from each other, are bound together. A "G" (which stands for guanine) can only be across from a "C" (which stands for cytosine). An "A" (which stands for adenine) can only be across from a "T" (which stands for thymine). Thus, when one sequences a gene one actually works with complimentary strands of DNA to determine the original sequence of the gene.

Take Lesson 3 Quiz

Back to Top