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Questions and Answers
What is the total number of codons in the genetic code?
What is the total number of codons in the genetic code?
Which of the following statements about the genetic code is NOT true?
Which of the following statements about the genetic code is NOT true?
What feature of the genetic code allows for some amino acids to be represented by multiple codons?
What feature of the genetic code allows for some amino acids to be represented by multiple codons?
What type of codons do UAA, UAG, and UGA represent in the genetic code?
What type of codons do UAA, UAG, and UGA represent in the genetic code?
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How are the codons organized in a complete genetic code?
How are the codons organized in a complete genetic code?
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Which characteristic of the genetic code ensures that no codon overlaps with another?
Which characteristic of the genetic code ensures that no codon overlaps with another?
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What is the purpose of the translation process in protein synthesis?
What is the purpose of the translation process in protein synthesis?
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What is the sequence direction in which codons are read during protein synthesis?
What is the sequence direction in which codons are read during protein synthesis?
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What is the initiation codon in the genetic code?
What is the initiation codon in the genetic code?
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Which of the following statements accurately describes a key feature of the genetic code?
Which of the following statements accurately describes a key feature of the genetic code?
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How many codons in the genetic code do not code for amino acids?
How many codons in the genetic code do not code for amino acids?
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What is meant by the term 'degenerate code' in the context of the genetic code?
What is meant by the term 'degenerate code' in the context of the genetic code?
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Which of the following characteristics is NOT associated with the genetic code?
Which of the following characteristics is NOT associated with the genetic code?
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Which codon always initiates protein synthesis in eukaryotes?
Which codon always initiates protein synthesis in eukaryotes?
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What does it mean for the genetic code to be 'commaless'?
What does it mean for the genetic code to be 'commaless'?
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In prokaryotes, what is the modified form of methionine involved in protein synthesis?
In prokaryotes, what is the modified form of methionine involved in protein synthesis?
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Which statement regarding triplet codons is correct?
Which statement regarding triplet codons is correct?
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What is meant by the degeneracy of the genetic code?
What is meant by the degeneracy of the genetic code?
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Which of the following codons functions as the initiator codon in protein synthesis?
Which of the following codons functions as the initiator codon in protein synthesis?
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What characteristic do all codons share across different species?
What characteristic do all codons share across different species?
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What role do terminator codons play in protein synthesis?
What role do terminator codons play in protein synthesis?
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How does the Wobble Hypothesis explain certain codons encoding the same amino acid?
How does the Wobble Hypothesis explain certain codons encoding the same amino acid?
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Which of the following statements best describes the characteristic of the genetic code being 'unambiguous'?
Which of the following statements best describes the characteristic of the genetic code being 'unambiguous'?
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Why is redundancy in the genetic code advantageous?
Why is redundancy in the genetic code advantageous?
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Which mitochondrial codon exceptions indicate amino acids instead of termination?
Which mitochondrial codon exceptions indicate amino acids instead of termination?
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What is the result when the RNA sequence AAAAAA is used in the experiments?
What is the result when the RNA sequence AAAAAA is used in the experiments?
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What role do release factors play in protein synthesis termination?
What role do release factors play in protein synthesis termination?
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In Nirenberg and Matthaei's experiments, what was used to determine the amino acids specified by different codons?
In Nirenberg and Matthaei's experiments, what was used to determine the amino acids specified by different codons?
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What happens to the polypeptide chain during the termination of translation?
What happens to the polypeptide chain during the termination of translation?
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Which of the following codons is a termination codon in the cytoplasm?
Which of the following codons is a termination codon in the cytoplasm?
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What was the significance of studying codons composed of only one type of base in the experiments?
What was the significance of studying codons composed of only one type of base in the experiments?
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Which amino acid corresponds to the RNA sequence CCCCCC according to the experiments?
Which amino acid corresponds to the RNA sequence CCCCCC according to the experiments?
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What is the role of initiation factor 3 (IF-3) in the initiation of translation?
What is the role of initiation factor 3 (IF-3) in the initiation of translation?
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Which component forms a complex with initiation factor 2 (IF-2) during the initiation of translation?
Which component forms a complex with initiation factor 2 (IF-2) during the initiation of translation?
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What occurs when GTP is hydrolyzed during the initiation of translation?
What occurs when GTP is hydrolyzed during the initiation of translation?
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What is the final result after the large subunit binds to the initiation complex?
What is the final result after the large subunit binds to the initiation complex?
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During translation termination, what happens to the polypeptide chain?
During translation termination, what happens to the polypeptide chain?
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What is the significance of the 70S initiation complex in translation?
What is the significance of the 70S initiation complex in translation?
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How is the release factor involved in the process of translation termination?
How is the release factor involved in the process of translation termination?
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What prevents the large ribosomal subunit from immediately associating with the small subunit during translation initiation?
What prevents the large ribosomal subunit from immediately associating with the small subunit during translation initiation?
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Study Notes
Genetic Code
- Genetic code is a set of rules that translates a sequence of nucleotides in DNA or RNA into a sequence of amino acids in a protein.
- It is a dictionary with codons as the words.
- Each codon is a triplet of nucleotides, and there are 64 possible codons.
- Three codons are non-sense codons, which do not code for any amino acid.
- The other 61 codons code for the 20 amino acids.
Genetic Code Table
- The genetic code table shows the correspondence between codons and amino acids.
- The table is organized by the first, second and third bases of the codon.
Features of the Genetic Code
- Universal: The same codons code for the same amino acids in all organisms.
- Non-ambiguous: Each codon codes for only one amino acid.
- Comma-less: Codons are read consecutively without punctuation.
- Degenerate: More than one codon can code for the same amino acid.
- Non-overlapping: Three consecutive bases code for one amino acid.
- Initiation codon: AUG is the start codon, which codes for methionine.
- Termination codons: UAA, UAG, and UGA are stop codons, which signal the end of protein synthesis.
Redundancy of the Genetic Code
- Different codons can specify the same amino acid.
- This is due to the degeneracy of the code.
- This makes it less likely that mutations will disrupt protein synthesis.
Complementary Base Pairing
- The three base codons on mRNA are complementary to the three base anticodons of tRNA.
- This is how tRNA molecules deliver the correct amino acid to the ribosome.
Wobble Hypothesis
- Proposed by Crick to explain how tRNA can recognize multiple codons.
- The third base in a codon can sometimes "wobble" or pair with more than one base in an anticodon.
- This allows for a limited level of flexibility in the codon-anticodon pairing.
- Allows cells to have fewer tRNAs than codons.
Universal
- The same codons specify the same amino acids in all species.
Terminator codons
- Three "nonsense" codons, UAA, UAG, and UGA, act as termination codons.
- They signal the end of protein synthesis.
Initiator codon
- AUG is typically the initiation codon.
- It codes for methionine.
Genetic Code - Universal
- The genetic code is universal with some exceptions.
- Mitochondrial codons have some differences compared to cytoplasmic codons.
Nirenberg & Matthaei experiments
- These experiments used synthetic mRNA to determine what amino acids were coded by different codons.
- They found that the codon UUU codes for phenylalanine, AAA for lysine, and CCC for proline.
Ribosome
- The ribosome is the site of protein synthesis.
- It has two subunits: a small subunit and a large subunit.
- The small subunit binds to mRNA and the large subunit binds to tRNA.
Nirenberg-Leder Experiment
- Used a filter-binding assay to determine the codons that code for specific amino acids.
- The experiment involved preparing a cell extract containing ribosomes, tRNAs, and amino acids.
- They added different synthetic mRNA sequences to the extract, and analyzed the results.
Protein Synthesis Termination
- Stop codons signal the end of protein synthesis.
- Release factors bind to the stop codons and cause the polypeptide chain to be released from the ribosome.
- Hydrolysis of GTP releases the release factors and the tRNA from the ribosome.
Initiation of Translation
- The ribosome is made up of two subunits: a small subunit and a large subunit.
- Initiation factor 3 (IF-3) prevents the large subunit from associating with the small subunit.
- The small subunit binds to the mRNA.
- A tRNA charged with N-formylmethionine binds to the initiation codon on the mRNA.
- The large subunit binds to the complex, creating a complete initiation complex.
Nirenberg-Leder Experiment
- Used a filter-binding assay to determine the codons that code for specific amino acids.
- The experiment involved preparing a cell extract containing ribosomes, tRNAs, and amino acids.
- They added different synthetic mRNA sequences to the extract, and analyzed the results.
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Description
This quiz delves into the genetic code, exploring its structure and function in the translation of nucleotides to amino acids. Understand the universal nature, non-ambiguous definitions, and the organization of the genetic code table. Test your knowledge on codons and their corresponding amino acids.
