Question

Which of the following statements is incorrect about the recognition sites of restriction endonucleases?

• A. Each restriction endonuclease recognises a specific palindromic nucleotide sequence in the DNA
• B. The recognition sequence for different endonuclease could be 4, 6, or 8 base pairs
• C. The palindrome sequence reads the same on the two strands in both 5'- 3' and 3'- 5' orientations
• D. Restriction endonuclease finds the restriction site by inspecting the length of the DNA

Answer 1

The correct option is C The palindrome sequence reads the same on the two strands in both 5'- 3' and 3'- 5' orientations

Restriction endonuclease recognizes specific nucleotide sequences by inspecting the length of the DNA molecule, often a palindrome known as restriction site, and cleaves the DNA at a specific nucleotide within the restriction site. The recognition sequence for different endonucleases could be 4,6, or 8 base pairs long.
The palindrome sequence reads the same on the two strands only when the orientation of the reading is kept the same.
For example, the palindromic recognition sequence of EcoRI is
As seen above, in both strands the sequence is GAATTC if read in 5' - 3' orientation.