Transcription

Why does transcription need to happen?

Protein synthesis occurs in the cytoplasm at ribosomes, but a chromosomal DNA molecule is too large to leave the nucleus to supply the coding information needed to determine the protein’s amino acid sequence- base sequences of genes are copied and transported to ribosomes

Where does transcription occur?

In the nucleus

What does RNA polymerase do?

Unzips DNA and adds RNA nucleotides which pair wth complementary bases exposed on the template strand when the DNA unzips

How does RNA polymerase move?

Along the template strand in the 3’ to 5’ direction, so the mRNA molecule grows in the 5’ to 3 direction

What is the sense strand?

Contains the code for the protein to be synthesised, it runs from 5’ to 3’

What is the template strand?

RNA nucleotides only pair with the bases on this strand, used to produce mRNA molecule

What is the coding strand?

Based sequence of this strand is the same as the base sequence of the mRNA transcript but U replaces T

How does transcription stop?

RNA polymerase moves along the DNA until it reaches a terminator sequence. RNA polymerase releases the new mRNA strand

How does mRNA leave the nucleus?

Via nuclear pores in nuclear membrane to reach the cytoplasm