1) A wild-type polypeptideconsists of 27 amino acids. Many mutants have been dis

Question

1)      A wild-type polypeptideconsists of 27 amino acids. Many mutants have been discovered thatproduce versions of this polypeptide that are longer than normal.These mutations are each due to a substitution of a singlebase.

a.       What kind of mutation isresponsible?

b.      Do you expect the first 27amino acids in the mutant polypeptides to have the same sequence asthat in the wild type? Why or why not?

c.       Consult the genetic codeto determine what amino acids could occupy the 28thposition in the mutant polypeptides.

Explanation / Answer

      a.) As it is mentionedthat the mutation in wild type polypeptide which consisted of27 amino acids produced versions           ofpolypeptides which are longer than the normal, and these are eachdue to the substitution of single base, the kind           ofmutation that is responsible for this is Frame shiftmutations           Inspecific it is insertion mutations.          A frameshift mutation causes a shift in the reading frame either due toinsertion or deletions of bases.          In this,as it is mentioned that the mutant polypeptide is larger than thewild type polypeptide, the mutation that has          occurredin this will be definitely insertion.       b.) If the insertion of abase has occurred at the begining of the reading frame of the the27 amino acids; definitely there
          wouldnot be the same sequence for the first 27 amino acids as that ofthe wild type.           This isbecause by the addition of the base at the first position of thepolypeptide, the reading frame of the           polypeptidechanges which alters the next bases and codes for other aminoacids.           If thesingel base is inserted at the last position of the reading frame,then the sequence of amino acids in the mutant          willhave the same sequence as that of the wild type.          If thebase is inserted in between the bases, it depends on the codon thatcodes for the amino acids that are present.
      c.) Without knowing thesequence of the earlier amino acids or the sequence of m-RNA of thewild type polypeptide, it             isnot possible to say which amino acid will be occupying the28th position.

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.