One strand ofa section of DNA isolated from E. coli reads:
5' - GCA TAT GGC CTC CTC CGA GGA CGT CAT CAA - 3'
A. Suppose mRNA is transcribed from this DNA using the complementary strand as a template. What is the sequence of the mRNA? Write the sequence such that it reads 5' → 3' from left to right.
B. Disregarding translational start sites, write the sequences of the three longest polypeptides that would be made from this mRNA. Use three-letter abbreviations for individual amino acids.
A DNA strand can be used as template for transcription. This process will create an mRNA equivalent of the template strand. This mRNA can then be used as template for translation and the polypeptide sequence can be determined by using the genetic code as guide.
In transcription, the template strand will be copied starting from the 3' end as the RNA polymerase can only synthesize the polynucleotide in a 5' to 3' manner. For the problem, the template strand was said the strand complementary to the given strand. This then would have a 3' to 5' orientation.