Translation and Gene Regulation (Lec 7) Flashcards
3 Early Advances in understanding Protein Synthesis
- Proteins synthesized at Ribosomes
- Amino acids activated for synthesis by attachment to tRNA via aminoacyl-tRNA synthetases
- tRNA acts as an ‘adapter’ to translate mRNA into Proteins
Non-overlapping Code
Every 3 nucleotides (codon) in a sequence code for a specific protein
Universal Start Codon
AUG = Met (Methionine)
Termination Codons
UAA, UAG, UGA (Stop!)
Genetic Code Redundancy
Only 20 Amino Acids with 61 possible codons
Synonymous Mutations (Silent Mutations)
Single nucleotide is changed, leads to identical amino acid being produced. Protein function unaffected
Missense Mutations (Nonsynonymous)
Leads to an alternate amino acid being produced. Can result in non-functional protein
Nonsense Mutation
Change results in conversion to a STOP codon. Results in shortened polypeptide and non-functional protein
Frame Shift Mutation
Insertion or Deletion of a single nucleotide base causes a shift in the Reading Frame
Molecular Recognition of Codons
mRNA codon sequence is complementary to the tRNA anticodon sequence. They bind via H Bonds and align in an antiparallel manner
Protein Synthesis: Stages
- Activation of Amino Acids
- Initiation of Translation
- Elongation
- Termination and Ribosome Recycling
- Folding and Post-Translation Processing
Post Translational Modifications
Include enzymatic removal of formyl group, start codon, and sometimes additional residues, attaching carbohydrates, removing sequence to activate enzyme
Transcriptional Control
Primary means of regulating gene expression. Promoters determine the transcription start site and direct binding of RNA Pol II
Repressors
Reduce RNA Pol-promoter interactions or block the polymerase. Bind to operator sequences on DNA
Effectors
Bind to repressor and induces a conformational change
