Create a function that can determine whether or not an arbitrary DNA string is a Watson-Crick palindrome. The function will take a DNA string and output a true value if the string is a Watson-Crick palindrome and a false value if it is not. (True and False can also be represented as 1 and 0, respectively.)

The DNA string may either be in all uppercase or all lowercase depending on your preference.

Also, the DNA string will not be empty.


A DNA string is a Watson-Crick palindrome when the complement of its reverse is equal to itself.

Given a DNA string, first reverse it, and then complement each character according to the DNA bases (A ↔ T and C ↔ G). If the original string is equal to the complemented-reverse string, it is a Watson-Crick palindrome.

For more, see this question. It is a different challenge where you must find the longest substring of a DNA string where that substring is a Watson-Crick palindrome.


This is code-golf and the shortest code wins.

Test Cases

The format is <input> = <output>.

AGT = false
GCAGTGA = false
GCGC = true
ACTG = false
  • \$\begingroup\$ Related. \$\endgroup\$ – Martin Ender Apr 25 '16 at 6:39
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    \$\begingroup\$ Someone should write a program in DNA# that is also a Watson-Crick palindrome. :D (might not be possible) \$\endgroup\$ – mbomb007 Apr 25 '16 at 16:49
  • \$\begingroup\$ Or, if you like, "a word is a Watson–Crick palindrome if it has order 2 in the free group on 2 generators" (or on n generators!). \$\endgroup\$ – wchargin Apr 26 '16 at 3:19
  • \$\begingroup\$ (I guess technically that's "order at most 2.") \$\endgroup\$ – wchargin Apr 26 '16 at 3:19
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    \$\begingroup\$ @AndrasDeak According to Watsons book, Franklin was apparently mostly a thorn in their side. She repeatedly refused to hand over x-rays showing the helix (as I recall), because she refused to believe it. Its worth a read if you are interested in the discovery at any rate. \$\endgroup\$ – Obsidian Phoenix Apr 27 '16 at 15:19

32 Answers 32


J, 19 bytes


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Wolfram Language (Mathematica), 45 bytes


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Converts A to 10, T to 7, C to 12, and G to 5, by taking the ASCII codes mod 11 with offset 2. Then checks if the resulting list and its reverse add to 17 in each coordinate.


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