Question

im studying the action of RNA polymerase during transcripion. and i want to know what type of bases are added to the growing mRNA by RNA polymears

Answer 1

Transcription is when a segment of DNA is used to produce a complementary mRNA molecule. This process uses an enzyme called RNA polymerase, similar in form and function to DNA polymerase.

First, the RNA polymerase binds to a DNA molecule and separates its two strands.
One strand of the DNA serves as a template to assemble nucleotides together into a complementary mRNA strand.

Specific base sequences on the DNA molecule, called promoters, signal where the RNA polymerase should begin transcribing a section of mRNA. Other base sequences on the DNA then signal that the new mRNA molecule is complete, and transcription stops.
Like in DNA base pairing, each base on the DNA strand has only one base it will pair with on the new mRNA strand. RNA contains the nitrogenous base uracil (U) instead of thymine. This means that wherever the DNA strand has adenine (A), the complementary mRNA strand will have uracil (U). Notice that RNA is a single strand; it does not exist as a double helix like DNA.