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Assignment 2
 

Assignment 2

Imagine that you have just purified a new protein from the brain of adolescent males that you believe may be responsible for excessive hair-combing behavior. From peptide-sequencing experiments, you have determined that this protein contains repeats of the following peptide sequence: Trp-Met-Asp-Gly. Determining the nucleotide sequence of mRNA that was used to translate this part of the protein will enable you to identify the chromosomal location of this new gene and allow you to isolate and clone this gene. It is known that this peptide sequence is highly conserved among males that demonstrate excessive hair-combing behavior which suggests that this portion of the protein is important for its functions. In addition, a mutant form of this protein has also been discovered that appears to result in the loss of the excessive hair-combing behavior. This mutant sequence arises from a single point mutation in the nucleotide sequence of the normal (wild-type) gene for this protein that creates alterations in the amino acid sequence of the protein produced. The peptide sequence from this mutant protein is Met-Tyr-Val-Cys. Use TranslationLab to complete the following exercises.
1 .       Determine the sequence of a mRNA that could be used to translate this peptide and enter it in the field below.  



2 .       Can you determine another sequence of mRNA that would also code for this peptide? Why or why not? Explain your results in the field below.  



3 .       Once you have deciphered the mRNA sequence for the normal protein, introduce changes in this sequence until you have determined the nucleotide sequence that specifies the mutated peptide sequence. Examine this mRNA sequence and identify the codon or codon(s) that were altered to create the mutant peptide.  








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