Restriction enzymes: definition, characteristics and uses.

Definition: Restriction enzymes are like molecular scissors. They are proteins found in bacteria that can cut DNA at specific places. These places are called recognition sites, and they are usually short sequences of DNA that are palindromic, meaning they read the same backwards and forward.

Characteristics:

1. Specificity: Each restriction enzyme recognizes and cuts DNA at a specific sequence.
2. Palindromic Recognition Sites: These enzymes usually recognize palindromic sequences in the DNA, such as GAATTC, which reads the same in both directions.
3. Endonucleases: They are classified as endonucleases because they cut the DNA within the molecule, rather than at the ends.
4. Natural Defense Mechanism: In bacteria, restriction enzymes act as a defence mechanism against invading viruses (bacteriophages) by cutting up their DNA.

Uses:

1. DNA Cloning: Restriction enzymes are crucial in DNA cloning techniques. They are used to cut both the DNA to be cloned and the vector (often a plasmid) into which the DNA will be inserted.
2. Genetic Engineering: Restriction enzymes are fundamental tools in genetic engineering. They enable scientists to cut DNA at specific points and then join it with other DNA fragments. This allows the creation of genetically modified organisms (GMOs) and the manipulation of genes for various purposes, such as producing pharmaceuticals or improving crop yields.
3. DNA Analysis: Restriction enzymes are also used in DNA fingerprinting and other forms of DNA analysis. By cutting DNA at specific sites, scientists can create unique patterns that can be used to identify individuals or determine relationships between organisms.

In essence, restriction enzymes are vital tools in molecular biology, enabling scientists to manipulate and study DNA in a precise and controlled manner.