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Questions and Answers
What does the triplet code in the genetic code refer to?
What does the triplet code in the genetic code refer to?
What is the function of termination codons in translation?
What is the function of termination codons in translation?
Which component is crucial in the formation of the 30S preinitiation complex during initiation?
Which component is crucial in the formation of the 30S preinitiation complex during initiation?
During elongation in prokaryotic translation, what is the primary action that takes place?
During elongation in prokaryotic translation, what is the primary action that takes place?
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What role does RF3 play in the termination phase of translation?
What role does RF3 play in the termination phase of translation?
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What is a key characteristic of the genetic code that ensures it is universal?
What is a key characteristic of the genetic code that ensures it is universal?
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Which statement best describes posttranslational modifications?
Which statement best describes posttranslational modifications?
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Which of the following stages comes after the formation of the 70S initiation complex during translation?
Which of the following stages comes after the formation of the 70S initiation complex during translation?
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Study Notes
Discipline
- Discipline is not about perfection, but about continuity.
Genetic Code Translation
- Each human cell constructs up to 7,500 ribosomes every minute.
- These ribosomes are intracellular factories that decode genetic instructions to produce proteins.
- Ribosomes are essential for protein synthesis.
Characteristics of the Genetic Code
- The genetic code is triplet.
- The genetic code is specific.
- The genetic code is degenerate.
- An initiation codon sets the reading frame (start signal).
- The genetic code is non-overlapping.
- Termination codons mark the end of the coding sequence (stop signal).
- The genetic code is universal.
Translation in Bacteria
- Translation in bacteria occurs cotranscriptionally, meaning it happens concurrently with transcription.
- The expressome includes the machinery for both transcription and translation.
- Ribosomes bind to mRNA at the Shine-Dalgarno sequence.
Translation in Prokaryotes - Stages
-
Initiation:
- Formation of 30S preinitiation complexes (30S PIC).
- Formation of 30S initiation complexes (30S IC).
- Formation of 70S initiation complexes (70S IC).
-
Elongation:
- Decoding
- Peptide bond formation
- Translocation
- Termination:
Initiation: 30S PIC
- IF3, IF2 + GTP, and IF1 bind to 30S.
- IF2 recruits fMet-tRNAfMet.
Initiation: 30S IC
- mRNA is recruited to the 30S PIC.
Initiation: 70S IC
- 50S joins the 30S IC, triggering IF dissociation.
- fMet-tRNAfMet is placed in the P site.
Elongation
- Decoding, peptide bond formation, translocation.
- EF-Tu brings aminoacyl-tRNA to the A site
- Peptide bond formation between amino acids
- Translocation moves ribosome along the mRNA.
- EF-G helps catalyze translocation.
Translation Termination
- Recognition of stop codons by RF1/2.
- Hydrolysis of peptidyl-tRNA bonds by the ribosome.
- Dissociation of RF1/2 by RF3.
- Dissociation of 30S and 50S ribosomal subunits.
- Release of tRNA, and mRNA.
Protein Structure
- The primary structure is the amino acid sequence.
- Interactions between amino acids cause folding into secondary structures like alpha helices.
- Secondary structures fold into tertiary structures.
- Two or more polypeptides can associate to form quaternary structures.
Posttranslational Modifications
- Covalent modifications to amino acids, changing structure and chemical properties.
- Common modifications include trimming, phosphorylation, glycosylation, acetylation, and methylation.
- Modifications can be reversible or irreversible.
tRNA Structure
- tRNA has a three-dimensional structure.
- tRNA has cloverleaf and space filling models
- Contains an anticodon loop, acceptor stem for amino acid attachment.
- Interactions between paired bases via hydrogen bonds.
- Specific anticodon interacts with mRNA codon.
Additional Information
- Kinetic Checkpoints during mRNA selection.
- Chaperonins assist in protein folding.
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