GRADED
Central Dogma
The process to create a functional protein.
DNA -->RNA-->Polypeptide
Transcription-->RNA processing-->Translation
Gene Expression
2 Steps
1) Transcription: info encoded in DNA is copied to mRNA in the nucleus.
2) Translation: A polypeptide is synthesized using info encoded in mRNA in the
ribosome.
Codons
There are 64 codons. Codons are redundant, meaning several codons can code for the
same amino acid..
- 61 code for amino acids.
- 3 code for STOP codons.
- 1 code for a START codon.
Transcription
1) Initiation: RNA polymerase unwinds DNA binding to the promoter (TATA Box) of DNA
sequence of the template strand.
2) Elongation: Starting at DNA's 3' end, RNA is produced in the 3'-->5' direction. Runs
anti-parallel to template strand.
3) Termination: RNA Pol hits a stop codon and detaches.
Template Strand
Is the template that RNA uses and runs antiparallel to the RNA strand. Runs 3' --> 5'.
Nontemplate Strand
Same sequence as the RNA strand. Runs 5' --> 3'.
RNA Processing
RNA modifications and RNA splicing.
- 5' end receives a G cap, protecting the transcript during transport.
- 3' end receives a poly-A tail, increases stability and mobility.
- extrons (code for specific domains) stay, introns are spliced out, done by ribozymes.
Translation
1) Initiation: Small ribosomal subunit binds to mRNA and large ribosomal subunit
brought in by initiation factors, creating the initiation complex.
2) Elongation: tRNAs arrive at the A site charged with an amino acid, move into the P
site to elongate the polypeptide, and shift to the E site once done transferring amino
acid.
3) Termination: Ribosome reaches a stop codon to stop coding and a release factor
enter the A site, creating a hydrolysis reaction and causing the initiation complex to split.
Third Position Wobble