Question

One strand of a section of DNA isolated from E. coli reads: Suppose that an mRNA is transcribed from this DNA using the complementary strand as a template. What will the sequence of the mRNA in this region be? What is the amino acid sequence of the proteins? Would the same proteins be made if the other strand of DNA served as template for transcription? Why or why not? If the T underlined in the above sequence was to go through a transition mutation, what would the new mRNA strand be? Using the mRNA strand for answer d, translate the three feading frames. Using the amino acid sequences from e, predict the effect of the transition mutation on the protein. Describe the steps of protein synthesis, beginning with the attachment of a messenger RNA molecule to the small subunit of a ribosome and ending with the release of the polypeptide from the ribosome. Include in your

Answer 1

a). The sequence of the mRNA in this region will be :
5' GUAGCCUACCCAUAGG -3'
b). The amino acid sequence of the proteins is as follows:
Val-Ala-Tyr-Pro-stop
c). No, the same protein would not be made if the other strand of DNA served as the template for transcription.This is because the two strands of DNA are not similar in their sequences rather they are complementary to each other,so the mRNA synthesized from each of them will have different sequences.
d). If the T underlined in the above sequence undergoes a transition mutation then, the above sequence will be changed to :5' GTAGCCCACCCATAGG -3'
The new mRNA strand will be :
5' GUAGCCCACCCAUAGG -3'
e). Using the mRNA strand for answer d ,the reading frames:
Val-Ala-His-Pro-stop
f). Due to the transition mutation Tyr in the 3rd position of the native protein has been changed to His in the mutated protein.As a result of this some of the properties of the protein will be changed as Tyr is an aromatic polar amino acid whereas His is a basic amino acid of polar nature.
Though both are polar but His is positively charged and Tyr is not.

Q2 is incomplete.