Question

Which one of the following represents a palindromic sequence in DNA?

• A. 5$^{'}$ - CGTATG - 3$^{'}$
  3$^{'}$ - GCATAC - 5$^{'}$
• B. 5$^{'}$- CGAATG - 3$^{'}$
  3$^{'}$ - CGAATG - 5$^{'}$
• C. 5$^{'}$ - GAATTC - 3$^{'}$
  3$^{'}$ - CTTAAG - 5$^{'}$
• D. 5$^{'}$ - GACTAC - 3$^{'}$
  3$^{'}$ - TACGAC - 5$^{'}$

Answer 1

Answer: (C)

The palindromes in DNA are base pair sequences that are the same when read forward (left to right) or backward (right to left) from a central axis of symmetry. The following sequence reads the same on the two strands in 5' $\to$ 3' direction. This is also true when we read in the 3' $\to$ 5' direction.
$A \xleftarrow{5^{\prime}-\text { GAATTC }-3^{\prime}}{ } B$
$A \xrightarrow{3^{\prime}-C T T A A G-5^{\prime}} B$ Palindromic sequence
Restriction endonuclease enzymes recognize palindromic sequences in DNA and cut them.