Protocol Online logo
Top : New Forum Archives (2009-): : Molecular Biology

Orientation of primers - (Oct/19/2011 )

Hi all,
This is a stupid question but it has stumped me..I am looking at the pcr2.1 vector map. Why does the m13 reverse start at what I would call the 5'' (nearest postion 1, at about 201bp) postition end and the forward at 3"end (pos 391)?
Here is a link to the vector map
Thanks in advance


I think the reason you're confused is because the LacZ/Lac operon is going in the opposite direction as the T7 Promoter. The numbering for the plasmid is actually reversed relative to the direction of T7 transcription, so the M13 promoters are in the same orientation as the potential T7 transcript, but opposite to the Lac sequences and the plasmid numbering. I know, I know, I hate it when plasmids are numbered/arranged this way, but everybody does it differently.


thanks for the reply allynspear! It seems a bit silly to number this way alright!