RNA polymerase is the enzyme used to bind the DNA section of interest and recruit the free bases needed to form a new mRNA strand. DNA is transcribed on to an mRNA strand because it is too large to leave the nucleus and mRNA is single stranded with the ability to leave the nucleus and enter the cytoplasm of the cell, where translation can occur (the production of polypeptide chains from messenger RNA using ribosomes and tRNA).The antisense strand is read (5' to 3' direction) and RNA polymerase and forms a complementary mRNA sequence with this strand. The sense strand is NOT transcribedthe new mRNA strand leaves the nucleus and enters the cytoplasm where it is used by ribosomes (that either roam the cell freely or are attached to the rough endoplasmic reticulum)for translation.