palindromic sequence

A nucleic acid sequence in a double-stranded DNA or RNA molecule whereby reading in a certain direction (e.g. 5' to 3') on one strand is identical to the sequence in the same direction (e.g. 5' to 3') on the complementary strand.

Since a double helix is formed by two paired antiparallel strands of nucleotides that run in opposite directions, and the nucleotides always pair in the same way (adenine (A) with thymine (T) in DNA or uracil (U) in RNA, cytosine (C) with guanine (G)), a single-stranded nucleotide sequence is said to be a palindrome if it is equal to its reverse complement.

It can be seen in peptide sequences that make up proteins and tends to form alpha helices.

Many restriction enzymes (restriction endonucleases) recognize specific palindromic sequences and cut them. For example, the EcoR1 (restriction enzyme) by Escherichia coli recognizes a pair of strand reads, 5'-GAATTC-3' and 3'-CTTAAG-5'.

Cf. stem-loop