Lecture 15
From Gene to Protein
ribose
deoxyribose
H
• Transcription:
• The synthesis of RNA
using DNA as the
template
• Occurs in the nucleus
• Translation
• The synthesis of protein
using mRNA as the
template
• Occurs in the cytoplasm
• Requires ribosomes
(free or attached to the
rough ER)
Basic organization of a gene…..
Sequence-specific TFs
promoter
TATA
transcription unit
Transcription
Transcription - Initiation
Transcriptional Initiation: promoter of a gene
TATA box-binding factor (TBP) and other
general transcription factors
RNA polymerase
Sequence-specific transcription factors
Elongation
• ribonucleotides are added to the growing
chain by RNA polymerase II
• uses DNA sequence as template
• 5’ to 3’ synthesis (anti-parallel to DNA)
• opens up 10-20 base pairs at a time
• new RNA strand peels away from the DNA
template as it is synthesized
Termination
• termination: when polyadenylation signal
is reached (AAUAAA)
• 1-35 nucleotides downstream – pre-mRNA
is cut free from the RNA polymerase
• RNA Polymerase continues on for
hundreds of nucleotides….
Modification and Processing
(1) 5’ methylated cap
(2) 3’ poly A tail
(3) splicing
Translation - tRNA
Translation – the mRNA code
Translation: Initiation, Elongation and Termination
1. Initiation
2. Elongation
3. Termination