Question

What is considered to be key to make DNA fragments?

Answer 1

Restriction enzyme:

1. Restriction enzyme, also known as restriction endonuclease, is a protein produced by bacteria that cleaves DNA at specific sites along the molecule.
2. The restriction enzyme cleaves the DNA sequence asymmetrically to produce short and single-stranded structures which are called sticky or cohesive ends because these can stick together on treatment with a ligase to form the DNA molecule again.
3. Each restriction enzyme recognizes a different and specific recognition site or DNA sequence.
4. Thus, restriction enzyme is the key to make DNA fragments.

Example:

1. A six nucleotide palindromic sequence recognized by the restriction enzyme EcoR1 cleaves both strands of DNA at different locations.
2. So, when two DNA samples are treated and cleaved with a similar sticky end restriction enzyme then the fragments of different lengths of DNA sequence are observed because in both DNA sequences the recognition or restriction site would be different.