1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Dna/rna Strands

  1. Apr 7, 2008 #1


    One problem, when using the genetic code we have an extra nitrogenous base. What to do?

    Thanks :)
  2. jcsd
  3. Apr 7, 2008 #2
    The extra base(s) might not code for anything. You need to look for the start codon.
  4. Apr 7, 2008 #3
    one problem i don't think there is a start codon there
  5. Apr 7, 2008 #4
    In that case, the sequence you just listed could be part of an untranslated region in the DNA, or it could also be a translated region. It's just one segment of the DNA. Without any questions concerned with it, that's as much as you can know.
  6. Apr 7, 2008 #5
    wow weird this assignment tells me to code it's amino acid sequence :( And there is no start codon.
  7. Apr 7, 2008 #6
    But I do see a start codon. Look closer.
  8. Apr 7, 2008 #7
    umm gug, but that's only one thing :( and then the next question would be like, adding a G to the eigth nucleotide of the DNA template, why is the mRNA (amino acids) sequence shorter. BUt instead it would be longer as GUG occurs earlier.
  9. Apr 7, 2008 #8
    GUG is not a start codon. Your start codons in DNA start with TAC from the 3' to 5' end.
    Last edited: Apr 7, 2008
  10. Apr 7, 2008 #9
    ohh so it would start on the uac? we have to code for mRNA
  11. Apr 7, 2008 #10

    EDIT: whoops, Gannon is correct.
    Last edited: Apr 7, 2008
  12. Apr 7, 2008 #11
    ok thanks.
  13. Apr 7, 2008 #12
    If there is no start codon present, you can usually assume that the sequence given is in the middle of a region being translated. It usually isn't a trick question about "there's no start codon, so no polypeptide is produced." There may be a stop codon present as well, which would terminate translation, but again, if there is none then the strand is a mid-region. As for the extra base, it is negligible because obviously no amino acid has a guanine-only tRNA complement.
  14. Apr 7, 2008 #13
    No. The only start codon sequence is that for methionine (AUG). UAC is one of two sequences for tyrosine.
    Last edited: Apr 7, 2008
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook