Podcast
Questions and Answers
What does the 'one gene-one polypeptide' hypothesis suggest?
What does the 'one gene-one polypeptide' hypothesis suggest?
- Each gene encodes for a single polypeptide. (correct)
- Each gene encodes for multiple proteins.
- Each gene encodes for a single enzyme.
- Each gene is responsible for multiple traits.
Why is the genetic code described as degenerate?
Why is the genetic code described as degenerate?
- Most amino acids are specified by more than one codon. (correct)
- All amino acids are coded by exactly one codon.
- Most codons specify more than one amino acid.
- Some codons do not code for any amino acids.
What is the main role of the tRNA during translation?
What is the main role of the tRNA during translation?
- To synthesize proteins directly.
- To transport ribosomes to the mRNA.
- To catalyze the peptide bond formation between amino acids.
- To carry amino acids to the ribosome and match codons. (correct)
What distinguishes bacterial initiator tRNA from eukaryotic initiator tRNA during translation initiation?
What distinguishes bacterial initiator tRNA from eukaryotic initiator tRNA during translation initiation?
What occurs during the termination stage of translation?
What occurs during the termination stage of translation?
Which amino acids are exceptions to the concept of the degenerate code?
Which amino acids are exceptions to the concept of the degenerate code?
What role do elongation factors EF-Tu and EF-G play during translation?
What role do elongation factors EF-Tu and EF-G play during translation?
Which statement accurately represents a key difference in initiator tRNA usage between bacteria and eukaryotes?
Which statement accurately represents a key difference in initiator tRNA usage between bacteria and eukaryotes?
What is the significance of the Wobble Hypothesis in translation?
What is the significance of the Wobble Hypothesis in translation?
How many nucleotide combinations are available in the genetic code, and what does this allow for?
How many nucleotide combinations are available in the genetic code, and what does this allow for?
What is a consequence of the Wobble Hypothesis in protein synthesis?
What is a consequence of the Wobble Hypothesis in protein synthesis?
How does the degenerate nature of the genetic code benefit organisms?
How does the degenerate nature of the genetic code benefit organisms?
What is the primary role of peptidyl transferase during elongation in translation?
What is the primary role of peptidyl transferase during elongation in translation?
Which statement correctly describes the initiation phase of translation in eukaryotes?
Which statement correctly describes the initiation phase of translation in eukaryotes?
Which of the following best describes the concept of 'one gene-one enzyme' as proposed by Beadle and Tatum?
Which of the following best describes the concept of 'one gene-one enzyme' as proposed by Beadle and Tatum?
Flashcards
Gene function
Gene function
Genes are DNA segments directing protein production.
One gene-one polypeptide
One gene-one polypeptide
A gene largely dictates the production of a single polypeptide chain (protein).
Degenerate code
Degenerate code
Multiple codons can specify the same amino acid.
tRNA function
tRNA function
tRNA carries amino acids to ribosomes, matching anticodons to mRNA codons.
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Translation Initiation
Translation Initiation
mRNA and initiator tRNA bind to the ribosome to start protein synthesis.
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Inborn errors of metabolism
Inborn errors of metabolism
Genetic defects that disrupt enzyme function, leading to metabolic disorders.
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Shine-Dalgarno sequence
Shine-Dalgarno sequence
A specific nucleotide sequence in bacterial mRNA that helps initiate translation by binding to the small ribosomal subunit.
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Wobble hypothesis
Wobble hypothesis
Flexibility in base-pairing rules at the third codon position allows fewer tRNAs to recognize multiple codons.
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Peptidyl transferase
Peptidyl transferase
An enzyme within the ribosome responsible for creating peptide bonds between amino acids during translation.
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Release factors
Release factors
Proteins that recognize stop codons in mRNA, terminating translation.
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What did Beadle and Tatum discover?
What did Beadle and Tatum discover?
They proposed the "one gene-one enzyme" hypothesis, later refined to "one gene-one polypeptide," suggesting each gene dictates a specific protein.
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Why is the genetic code degenerate?
Why is the genetic code degenerate?
Most amino acids are encoded by multiple codons, but exceptions include tryptophan and methionine.
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What is the role of tRNA?
What is the role of tRNA?
Transfer RNA (tRNA) carries specific amino acids to the ribosome, matching its anticodon to the corresponding mRNA codon.
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What does the wobble hypothesis explain?
What does the wobble hypothesis explain?
The third position of a codon has flexible base-pairing rules, meaning fewer tRNAs are needed to recognize multiple codons.
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What is the key event in translation elongation?
What is the key event in translation elongation?
A charged tRNA enters the A site of the ribosome, and the peptidyl transferase enzyme forms a peptide bond between amino acids, extending the polypeptide chain.
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Gene Function and Hypotheses
- Genes are DNA segments coding for protein production.
- Garrod's "inborn error of metabolism" suggested genes control enzymes.
- Beadle and Tatum's "one gene-one enzyme" hypothesis broadened to "one gene-one polypeptide."
Degenerate Code and Triplet Codons
- Degenerate code: Multiple codons can code for the same amino acid (except tryptophan and methionine).
- Triplet codons: Three nucleotides form a codon, providing 64 combinations, sufficient for 20 amino acids.
tRNA and the Wobble Hypothesis
- tRNA: Transfers amino acids to ribosomes, matching anticodons to mRNA codons.
- Wobble hypothesis: Flexibility in third-base pairing reduces the number of tRNAs needed.
Translation
Initiation
- Small ribosomal subunit joins mRNA and initiator tRNA.
- Bacterial initiation tRNA is N-formylmethionine using Shine-Dalgarno sequence.
- Eukaryotic initiation tRNA involves the 5' cap and poly-A tail.
Elongation
- Charged tRNA enters the A site.
- Peptide bonds form (catalyzed by peptidyl transferase).
- Elongation factors (EF-Tu and EF-G) aid in tRNA addition and translocation.
Termination
- Release factors recognize stop codons.
- Translation ends, disassembling the ribosome complex.
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