Question

What do you mean by restriction enzymes? Explain with example.

Hint:

Restriction enzymes = molecular scissors. EcoRI and HindIII are commonly used in DNA technology.

Answer 1

Definition: Restriction enzymes, also called restriction endonucleases, are enzymes that cut DNA molecules at specific recognition sequences (usually palindromic sequences). They are also known as molecular scissors. Characteristics: \[\begin{array}{rl} \bullet & \text{They recognize short, specific DNA sequences (4–8 base pairs).} \\ \bullet & \text{They cut DNA at specific sites, producing either blunt ends or sticky ends.} \\ \bullet & \text{They were first discovered in bacteria, where they protect against invading viral DNA.} \\ \end{array}\] Example: - EcoRI: Recognizes the sequence \texttt{GAATTC} and cuts between G and A, producing sticky ends. - HindIII: Recognizes the sequence \texttt{AAGCTT} and cuts to produce sticky ends. Diagram (EcoRI Action): \[ \text{5' - GAATTC - 3'} \xrightarrow{\text{EcoRI}} \text{5' - G AATTC - 3'} \] \[ \text{3' - CTTAAG - 5'} \xrightarrow{\text{EcoRI}} \text{3' - CTTAA G - 5'} \] Importance: Restriction enzymes are widely used in recombinant DNA technology to cut and insert genes into vectors for genetic engineering.