Question

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

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

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.
$A\stackrel{5^{\prime }-\text{ GAATTC }-3^{\prime }}{\leftarrow }B$
$A\stackrel{3^{\prime }-CTTAAG-5^{\prime }}{\to }B$ Palindromic sequence
Restriction endonuclease enzymes recognize palindromic sequences in DNA and cut them.