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A little help...

Discussion in 'Pre-Medical - MD' started by Clipse, May 5, 2004.

  1. Clipse

    Clipse Member
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    This question has stumped my and I don't even know where to start:
    (a.) Explain the base changes leading to these protein sequences. Reconstruct a plausible nucleotide sequence.
    native: ? Arg Phe Phe Ser Pro ?
    (a.) ? Arg Phe Ser His Glu ?
    (b.) ? Arg Phe Phe
    (c.) ? Arg Phe Phe Pro?
    (d.) ? Arg Phe His Ser Pro?

    (b.) What would be the likely impact of the mutation shown on the expression of the protein? Where italicized, indicates the insertion of one base.

    CTT...AAT...GCC...CGG...TCG...ACC...GTA...CGT...GAG
    Leu....Asn....Ala....Arg....Ser....Thr....Val....Arg.....Glu

    :rolleyes: Any and all help appreciated.
     
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  3. calflowergirl

    calflowergirl Member
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    For the first question, you need to look at the codon table and see what are the possible codons for each of these aa. Then you can figure out if the mutation is a deletion, insertion, point mutation. For b) and c) there has to be a frameshift mutation because you end up with a shorter sequence.

    For the second question: anytime you insert a base pair you create a frameshift mutation which changes the grouping of nucleotide bases into codons. Look at the a.a. sequence and you can tell the difference.

    Hope this helped!
     
  4. Kalel

    Kalel Membership Revoked
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    I'm on call right now and there's not very much going on, so I spent ~1 hr trying to do your homework for you. After translating out the aa sequences, my conclusion is that for the first one, there are no simple mutations that explain the changes in sequence from the native ones to the new ones. They would require multiple nucleic acid insertions/deletions/rearrangements for them to work, so I'm convinced that you wrote them out incorrectly (I'm looking at the 9:47 edited version). The second one is just a matter of writing out the amino acid sequence based upon the nucleic acid sequence that you wrote out. I would write it out for you, but I'm too frustrated after wasting all that time on your first question. :mad:
     
  5. LA:)

    LA:) Member
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    i think kalel's right. assuming that the GLU was a typo & is actually GLN, read on...
    ----------------------------------
    some general substitution may help:
    C/U = Y
    G/A = R
    N = any base
    ----------------------------------

    ARG PHE PHE SER PRO
    CGN UUY UUY UCN CCN

    (delete bolded U base) =

    ARG PHE SER HIS GLN
    CGN UUY UYU CNC CN_

    (fill in using codes for ser, his & gln)

    ARG PHE SER HIS GLN
    CGN UUY UCU CAC CAR

    i think the next step is to delete the c in the SER to get a PHE...

    etc... you get the idea.

    i used this codon table http://sosnick.uchicago.edu/codon_table.html

    :luck:
     
  6. Clipse

    Clipse Member
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    I double checked and it is GLN, not GLU. So this only adds to the confusion :confused:

    I'm going to e-mail my prof. and see if there was a typo... hopefully there was, but I doubt it. I'll fill ya'll in. Thanks so much to everyone, for your efforts - esp. Kalel!
     
  7. IndyZX

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    holy crap, there are some very helpful people on this board
     
  8. Clipse

    Clipse Member
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    indyzx, you are indeed correct.

    So I talked to my prof. and 90 minutes later this is what i've figured out:

    There are several possible explanations, based on codon redundancies.

    Native: Arg Phe Phe Ser Pro ...
    CGC TTT TTC TCA CCA G...

    (a.) T deletion
    CGC TTT TCT CAC CAG...
    Arg Phe Ser His GluN

    (b.) C to G Inversion:
    CGC TTT TTC TGA CCA ...
    Arg Phe Phe Term

    (c.) TCA deletion
    CGC TTT TTC CCA ...
    Arg Phe Phe Pro

    (d.) T insertion
    CTG CTT TTT CTC ACC
    Leu Leu Phe Leu Thr



    Isn't genetics fun? :eek:
     

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