RNA synthesis

What is before and after the gene?

Promoter, 5’ UTR - 3’ UTR, Terminator

How many nucleotides are exposed at a time during the making of RNA?

about 17

What are the two stages of gene expression?

transcription and translation

How is the gene expression process organised in prokaryotes?

Transcription and translation are coupled: as soon as the mRNA comes out of RNA polymerase, it is translated by ribosomes

Why are transcription and translation not coupled in eukaryotes?

The two processes happen in different parts of the cell (nucleus and cytoplasm) and the RNA molecule exiting the RNA polymerase has yet to be processed

What steps compose the RNA processing to yield mRNA?

5’ capping, RNA splicing, 3’ polyadenylation

Does RNA polymerase need a primer?

no

What does RNA polymerase do during transcription?

It binds to the DNA, finds the promoter sequence, unwinds the double strand, breaks the hydrogen bonds, makes the RNA strand from the complementary template strand and catalyses the phosphodiester bonds between the nucleotides

How many base pairs of RNA/DNA hybrid can stay in the RNA polymerase active site?

around 8

In what direction is RNA synthesized?

5’ to 3’

What is the direction of the DNA template strand during transcription?

3’ to 5’

What happens once the RNA polymerase reaches the terminator sequence?

the RNA polymerase is released, the RNA molecule is released and the DNA returns to its original form

Is accuracy while making RNA as important as while making DNA?

No, because the cell makes multiple identical RNA molecules of the same gene, so if one has a mistake, the likelihood of a mutation is lower

Why does the terminator sequence have that effect?

It codes for a stem-and-loop structure in the RNA which causes the RNA polymerase to pause. The polyadenyl sequence is unstable and makes everything dissociate

Why is the stem-and-loop structure formed?

It is a palindromic sequence, meaning there are two sequences that are complementary to each other (they form the stem) separated by some bases (the loop). The sequence is also rich of G and C nucleotides.