Question

Which type of chemical bonds of DNA are cut by restriction endonucleases? Which are formed by DNA ligases?

Answer 1

1. A restriction enzyme or restriction endonuclease is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites
2. Restriction sites, or restriction recognition sites, are locations on a DNA molecule containing specific (4-8 base pairs in length[1]) sequences of nucleotides
3. For example, the common restriction enzyme EcoRI recognizes the palindromic sequence GAATTC and cuts between the G and the A on both the top and bottom strands
4. DNA ligase binds the breaks in the phosphate backbones of the nucleotides together to form a cohesive strand.
Restriction site depends upon the nucleotide which is present in the DNA. DNA ligase will be formed between the broken down phosphate nucleotides.