Transcription - (Jan/16/2019 )

The following segment of DNA encodes a polypeptide containing six amino acids. DNA triplets encoding the start codon and a stop codon are included in this sequence.

5' - ...CCCAGCCATGCCTTTGCAAGAGGCCATATCGAC... - 3'

3' - ...GGGTCGGATCGGAAACGTTCTCCGGTATAGCTG... - 5'

Identify the sequence and polarity of the mRNA encoded by this gene.

Please walk me through this as if I don't know anything about molecular genetics, even though I do.

You start, show how would you try to solve this question.

Well, usually I would first differentiate the template with the non-template strand to figure out which would be complimentary to the mRNA. In this case, I don't know which is the template strand. Is the start codon supposed to be in somewhere in the middle of the strand, and I don't see any stop codons they seem to have in the strand. Don't I need to find these to define the template strand?

Furthermore, I know that the mRNA has to be coded in the 3' to 5' direction, but that doesn't make any difference, does it? Also, the mRNA needs to have all its thymine bases replaces with uracil, but first I need to create the mRNA strand, which needs the template to figured out. I am pretty sure I am missing a piece of information, but I can't figure out what.

Start by finding a reference chart showing the nucleotide triplets that represent the codons for start, stop, and all the amino acids.  You are given the information that both a start and stop codon are present.  So hunt for them- they should be a certain distance apart, which you should be able to figure out based on the clue "6 amino acids." Start on the top strand; if you don't find any candidates there, try the bottom strand.  Hint; if you are reading the bottom strand, which direction should you be reading it?