Biology – Principles of genetic technology | e-Consult

Restriction enzymes are crucial tools in recombinant DNA technology. Their primary role is to cut DNA at specific sequences, creating DNA fragments of defined lengths.

Function: Restriction enzymes are a type of endonuclease – they cut DNA internally, rather than at the ends. They recognize specific DNA sequences, known as recognition sites or restriction sites. These sites are typically short, palindromic sequences (sequences that read the same forwards and backwards on opposite strands of DNA).

Recognition Sites: Different restriction enzymes recognize different sequences. These recognition sites are usually 4-8 base pairs long. There are two main types of restriction enzymes:

• Type I: Cleave DNA outside the recognition sequence.
• Type II: Cleave DNA precisely within the recognition sequence. This is the most commonly used type in recombinant DNA technology.
• Type III: Cleave DNA outside the recognition sequence, similar to Type I.

The specificity of restriction enzymes is essential for creating DNA fragments that can be easily inserted into a vector. The cut ends of the DNA fragments are often "sticky" (with single-stranded overhangs) or "blunt" (with no overhangs), which facilitates ligation with the vector.