Palindrome (; "again") and ' (; "way, direction"). Palindromes date back at least to 79 AD, as a palindrome was found as a graffito at Herculaneum, a city buried by ash in that year. This palindrome, called the Sator Square, consists of a sentence written in Latin: "Sator Arepo Tenet Opera Rotas" ("The sower Arepo holds with effort the wheels"). It is remarkable for the fact that the first letters of each word form the first word, the second letters form the second word, and so forth. Hence, it can be arranged into a word square that reads in four different
Palindrome world's longest palindromic word in everyday use. [[File:DNA palindrome.svg|thumb|600px|right|Palindrome of [[DNA structure]]A: Palindrome, B: Loop, C: Stem]] In most [[genome]]s or sets of [[gene]]tic instructions, palindromic motifs are found. The meaning of palindrome in the context of genetics is slightly different, however, from the definition used for words and sentences. Since the [[DNA]] is formed by two paired strands of [[nucleotides]], and the nucleotides always pair in the same way ([[Adenine]] (A) with [[Thymine]] (T), [[Cytosine]] (C) with [[Guanine]] (G)), a (single-stranded) sequence of DNA is said to be a palindrome if it is equal to its complementary sequence read