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Repetitive amino acid sequence

  1. Mar 2, 2017 #1
    If a protein contains a repetitive region, what might be assumed, and what should be done next to test the null hypothesis?

    Can anyone answer this with a reliable source they find?
  2. jcsd
  3. Mar 2, 2017 #2


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    Staff: Mentor

    When I Google your post, I get some pretty instructive hits. BTW, is this question for schoolwork?
  4. Mar 2, 2017 #3
    Yes, it's for a bioethics type of class. What did you Google specifically? I found a study that was conducted that pointed out there was just advantages to repeated amino acid sequences....
  5. Mar 2, 2017 #4


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    Staff: Mentor

    I copied your whole first sentence, and got a few hits that looked like they addressed your question.
  6. Mar 2, 2017 #5


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    Science Advisor

    Sounds like you might not have had biochemistry.

    Proteins are complex with a complex structure that is often analyzed by looking at the interactions between the string of amino acids that make them up.
    The interactions can be between amino acids close together or far apart in the string.
    Repeats could be of single amino acids or sequences of various lengths.

    Depending on the details there are many possible implications.
    Last edited: Mar 2, 2017
  7. Mar 2, 2017 #6
    The hits I see do not pertain to the question as whole.
  8. Mar 2, 2017 #7
    I did take a first semester Biochemistry course, but we never talked about what happens when amino acid sequences repeat. The question that I initially asked is really all that was asked in the homework I am doing for my Chemical Information System/Bioethics course.
  9. Mar 3, 2017 #8


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    Well reliable, never mind slightly weird way of putting the question, and having considerable bioethic aspects is to start with this article on Huntington's disease aka Huntington's Chorea https://en.wikipedia.org/wiki/Huntington's_disease#Genetic_mutation There are other diseases of similar causation, but this is the most common and most researched.

    When it arises ex novo it is due to the replication machinery having made as some kind of a slip and duplicating a triplet. One or more copies of one amino acid are inserted into the sequence. Unfortunately once this has happened it is more likely to happen again. That is why you see this complex inheritance at the phenotypic level, with effects worsening down generations.

    Maybe it is not too trivial to say at the start that if you find it, it means that having it is compatible with life, though not good health. The disease's relatively late onset, opposite too many other genetic diseases, is relevant to bioethics.

    Note that this example is a single amino acid residue repeat. (I don't know whether there are examples of longer repeats that theoretically should exist - they are less likely to give functional proteins.)

    A key word to use in searches is 'tandem repeats'.

    You will certainly need for bioethics to be pretty conversant with tandem repeats that happen in DNA outside coding regions, so not affecting any proteins or phenotype. These are of variable length which has made them very useful, among other things, associating the DNA to individuals for forensic purposes, and also ancestry tracing. https://en.wikipedia.org/wiki/Variable_number_tandem_repeat

    If you have any conceptual difficulties in your further reading come back and hopefully someone here can help you.
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