Which one of the following represents a palindromic sequence?

5'-GAATTC-3'

3'-CTTAAG-5'

The correct answer is Option (1) → 

5'-GAATTC-3'

3'-CTTAAG-5'

Each restriction endonuclease functions by ‘inspecting’ the length of a DNA sequence. Once it finds its specific recognition sequence, it will bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar -phosphate backbones. Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA.

The palindrome in DNA is a sequence of base pairs that reads same on the two strands when orientation of reading is kept the same. For example, the following sequences reads the same on the two strands in 5' → 3' direction. This is also true if read in the 3' → 5' direction.

5' —— GAATTC —— 3'

3' —— CTTAAG —— 5