Question

(a) Why are restriction endonucleases so called ? (b) What is a palindromic nucleotide sequence ? How do restriction endonucleases act on palindromic sites to create sticky ends ?

Answer 1

1. Restriction enzymes are DNA-cutting enzymes found in bacteria. In order to be able to sequence DNA, it is first necessary to cut it into smaller fragments, because they cut within the molecule, they are often called restriction endonucleases.

2. A palindromic sequence is a nucleic acid sequence on double-stranded DNA or RNA wherein reading 5' (five-prime) to 3' (three prime) forward on one strand matches the sequence reading 5' to 3' on the complementary strand with which it forms a double helix.

3. Restriction enzymes recognize a specific DNA sequence, normally between four and eight base pairs long. The A A T T C sequence to the 3' direction of the G is called an overhang. The restriction enzyme Eco RI makes sticky ends when it cuts DNA. If both sequences are cut with Eco RI, they can be joined together.