2 Replies Latest reply on Mar 13, 2013 8:27 AM by JoelMG

    "Substitute" function not working properly



      "Substitute" function not working properly


           I'd love help on this:  I'd like to take a DNA sequence (composed of A C G and T) and return the "reverse complement".  For example, the reverse complement of "AATTCC" would be "GGAATT" (A and T are complementary; C and G are complementary).  At the moment I'm breaking this up into two steps:

           First, I use a "Reverse" command (which I've defined) and I place the result into a new new text field.  This works perfectly.   CCCTTTCGTCTCGCGCG  is reversed to GCGCGCTCTGCTTTCCC .

           Last, I need to find the complement, by simply substituting A for T, C for G, G for C, and T for A  in the reversed sequence.  But what I have just is not working correctly:

           In the field "Reverse Oligo 1" I have   GCGCGCTCTGCTTTCCC 

           I use the calculation for a new field:

           Substitute (Reverse Oligo 1; ["A" ; "T"] ; ["G" ; "C"] ; ["T"; "A"]; ["C"; "G"])

           This yields:   GGGGGGAGAGGAAAGGG

           It should yield CGCGCGAGACGAAAGGG .  The "G" to "C" substitution is not working, while the other substitutions are working fine.  I've retyped this several times and switched things around, but it never works.

           Any advice?  Thanks.   Joel

        • 1. Re: "Substitute" function not working properly

               It's working correctly, but not as you want it to.

               The substitutions get performed one bracketed pair of values at a time from left to right.

               First thing it does is substitute "T" for "A"  and then "C" for "G". (["A" ; "T"] ; ["G" ; "C"])

               But once that is done it turns around and substitutes "A" for "T" and then "G" for "C" ( ["T"; "A"]; ["C"; "G"] )

               To get this to work, you'll need to do something like this:

               Substitute (Reverse Oligo 1; ["A" ; "x"] ; ["G" ; "y"] ; ["T"; "A"]; ["C"; "G"]; ["x" ; "T"] ; ["y" ; "C"])


          • 2. Re: "Substitute" function not working properly

                 My goodness, that makes perfect sense!!!!  Thank you.  This will be easy to fix.