Transcription and Translation

Transcription

The first step of gene expression where RNA polymerase reads a DNA template (3' to 5') to synthesize a complementary, antiparallel mRNA strand (5' to 3').

Initiation in transcription

RNA polymerase binds to promotor sequences

Elongation in transcription

RNA polymerase builds mRNA molecule

Termination in Transcription

RNA polymerase binds to the terminator sequence, releasing the RNA transcript

What must happen before the mRNA leaves the nucleus?

splicing (post-trnascriptional modifications) must occur before the mRNA leaves the nucleus. Splicing removes intron sequences, keep exons, and adds a 5’ methyl-G cap along with a 3’ poly-A tail

Translation

the second step of gene expression in which ribosomes in the cytoplasm or rough ER synthesizes proteins by decoding mRNA sequences into polypeptide chains

Initiation in translation

small and large subunits of ribosomes assembles around mRNA, and the initiator tRNA binds to the start codon (AUG, UGA)

Elongation in translation

ribosomes move along mRNA, adding amino acids to a growing polypeptide chain

Termination in translation

the ribosome releases a completed polypeptide chain upon encountering a stop codon (UGA)