This animation illustrates Sanger sequencing, one of the earliest methods used to sequence DNA.

Sanger sequencing was developed by Fred Sanger and his colleagues in 1977. As shown in the animation, this method involves replicating DNA in the presence of chemically altered nucleotides. These nucleotides stop the replication process whenever they are incorporated into a growing strand of DNA. This creates many short DNA strands of varying lengths, which can be ordered by length to determine the sequence of the original DNA.

Depending on students’ background, it may be helpful to pause the animation at various points to discuss different parts of the method.