Illustration includes three pictures.

1. Cutting DNA, captioned 'A restriction enzyme is like a key that fits only one lock. The EcoRI restriction enzyme can only recognize the base sequence GAATTC. It cuts each strand of DNA between the G and A bases, leaving single-stranded overhangs with the sequence AATT. The overhangs are called “sticky ends” because they can bond, or “stick,” to a DNA fragment with the complementary base sequence.'
2. Separating DNA, captioned 'Gel electrophoresis is used to separate DNA fragments. After being cut by restriction enzymes, the fragments are put into wells on a gel that is similar to a slice of gelatin. An electric voltage moves them across the gel. Shorter fragments move faster than longer fragments. Within an hour or two, the fragments all separate, each appearing as a band on the gel.'
3. Reading DNA, captioned 'A small proportion of dye-labeled nucleotides are used to make a complementary DNA strand. Each time a labeled nucleotide is added to the strand, DNA replication stops. Because each base was labeled with a different color, the result is color-coded DNA fragments of different lengths. When gel electrophoresis is used to separate the fragments, scientists can “read” the DNA sequence directly from the gel.'