Textbook Question
Assuming the genetic code is a triplet, what effect would the addition or loss of two nucleotides have on the reading frame? The addition or loss of three, six, or nine nucleotides?
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Ch. 13 - The Genetic Code and Transcription
Klug12th EditionConcepts of Genetics ISBN: 9780135564776
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Table of contents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Chapter 13, Problem 6
In a coding experiment using repeating copolymers, the following data were obtained:
AGG is known to code for arginine. Taking into account the wobble hypothesis, assign each of the four codons produced in the experiment to its correct amino acid.
Verified step by step guidance1
Step 1: Identify the known codon and its amino acid. The problem states that AGG codes for arginine (Arg). This gives us a starting point to analyze other codons with similar sequences.
Step 2: Recall the wobble hypothesis, which states that the third base of a codon can often vary without changing the amino acid it codes for. This means codons differing only in the third base may code for the same amino acid.
Step 3: Analyze the codons from the AG copolymer: AGA and GAG. Since AGG codes for Arg, and AGA differs only in the third base, AGA likely also codes for Arg. GAG differs in the first base and is associated with Glu in the table, so GAG codes for Glutamic acid (Glu).
Step 4: Analyze the codons from the AAG copolymer: AGA, AAG, and GAA. From previous steps, AGA codes for Arg. AAG differs in the third base from AAA, which is known to code for Lysine (Lys), so AAG likely codes for Lys. GAA is known to code for Glu.
Step 5: Assign each codon to its amino acid based on the wobble hypothesis and the given data: AGA - Arg, GAG - Glu, AAG - Lys, GAA - Glu.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
The Genetic Code and Codon-Amino Acid Relationship
The genetic code consists of triplet codons in mRNA that specify amino acids during protein synthesis. Each codon corresponds to a particular amino acid or a stop signal. Understanding which codons code for which amino acids is essential for interpreting polypeptide sequences from nucleotide sequences.
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The Genetic Code
Wobble Hypothesis
The wobble hypothesis explains that the third base of a codon can pair less strictly with the corresponding base of the tRNA anticodon, allowing some tRNAs to recognize multiple codons. This flexibility helps explain why different codons can code for the same amino acid, which is crucial for assigning codons to amino acids in the experiment.
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Repeating Copolymers and Codon Production
Repeating copolymers are sequences of nucleotides repeated in a pattern, producing specific sets of codons. Analyzing the codons produced by these copolymers helps identify the amino acids incorporated into the polypeptide. This concept is key to linking the experimental codons to their corresponding amino acids.
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Related Practice
Textbook Question
The mRNA formed from the repeating tetranucleotide UUAC incorporates only three amino acids, but the use of UAUC incorporates four amino acids. Why?
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Textbook Question
In studies using repeating copolymers, AC . . . incorporates threonine and histidine, and CAACAA . . . incorporates glutamine, asparagine, and threonine. What triplet code can definitely be assigned to threonine?
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Textbook Question
In the triplet binding technique, radioactivity remains on the filter when the amino acid corresponding to the codon is labeled. Explain the rationale for this technique.
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Textbook Question
When the amino acid sequences of insulin isolated from different organisms were determined, differences were noted. For example, alanine was substituted for threonine, serine for glycine, and valine for isoleucine at corresponding positions in the protein. List the single-base changes that could occur in codons of the genetic code to produce these amino acid changes.
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Textbook Question
In studies of the amino acid sequence of wild-type and mutant forms of tryptophan synthetase in E. coli, the following changes have been observed:
Determine a set of triplet codes in which only a single-nucleotide change produces each amino acid change.
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