Question

PLS, HOW DOES A RNA POLYMERASE KNOW WHAT DNA STRAND TO USE AS A GENE TEMPLATE IN THE TRANSCRIPTION UNIT DURING TRANSCRIPTION?

Answer 1

First, let me show you an example double strand of DNA.


5'-A T G C C A T-3'
3'-T A C G G T A-5'

Transcription always goes from 5' to 3'.
BUT the TEMPLATE strand is always the 3' to 5' strand.

If Transcription were going from the 5' to 3' of the TOP strand,
then the template strand would be the BOTTOM strand.

SO, the mRNA, made from Transcription, in this case, would be.....

5'-A U G C C A U-3'

This mRNA is complementary to the bottom 3' to 5' strand of DNA,
because again, that is the template strand.