Question

why type || of restriction endonuclease use in rDNA technology?

Answer 1

Type II Restriction Endonucleases

• A type II restriction endonucleases recognises a specific sequence in the DNA and cut the DNA at the recognised sequence.

• So the cutting is sequence specific.

• At present about 350 type II restriction endonucleases are isolated from various bacterial strains.

• They are named using the first letter of the genus name, the first two letters of the species name and the first letter of the strain from which the enzyme isolated.

• The type 2 restriction endonucleases mostly recognise palindromic sequences to cut the DNA.

• The palindromic sequence consists of 4 – 6 basepairs and it bilaterally symmertrical.

• The base sequence in one strand is same in the other strand while reading in reverse order.

• An axis or line cuts the palindromic sequence in to two identical halves,and is called axis of symmertry.

• Some restriction enzymes cut at the resrtiction site along the axis of symmetry while others cut it at either side of the axis of symmetry.