DNA Cleavage Enzymes: The Scissors of the Genome
Proteins that cleave DNA are known as endonucleases or restriction enzymes. These enzymes act like molecular scissors, cutting the DNA molecule at specific sequences.
Types of DNA Cleavage Enzymes
There are two main types of endonucleases:
- Restriction endonucleases: These enzymes recognize and cut specific DNA sequences, often palindromic sequences. They are used extensively in molecular biology for cloning and gene manipulation. Examples include EcoRI and HindIII.
- Exonucleases: These enzymes remove nucleotides from the ends of DNA strands. They play a role in DNA repair and replication.
Functions of DNA Cleavage Enzymes
- DNA repair: Endonucleases help repair damaged DNA by removing the damaged portion and allowing for its replacement with a correct sequence.
- Gene regulation: Endonucleases can control gene expression by cutting specific DNA sequences that regulate gene transcription.
- Immune defense: In bacteria, restriction endonucleases act as a defense mechanism against viral infection by cleaving the viral DNA.
- Genetic engineering: Restriction endonucleases are essential tools in genetic engineering, allowing scientists to cut and paste DNA fragments to create new genes or modify existing ones.
Practical Applications
- DNA fingerprinting: Restriction enzymes are used in DNA fingerprinting, a technique used to identify individuals based on their unique DNA profile.
- Gene therapy: Endonucleases are used in gene therapy to correct genetic defects by cutting out faulty genes and replacing them with healthy ones.
