Textbook Question
An experiment by Khorana and his colleagues translated a synthetic mRNA containing repeats of the trinucelotide UUG.
How many reading frames are possible in this mRNA?
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Ch. 9 - The Molecular Biology of Translation
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 9, Problem 25c
An experiment by Khorana and his colleagues translated a synthetic mRNA containing repeats of the trinucelotide UUG.
How does the result of this experiment help confirm the triplet nature of the genetic code?
Verified step by step guidance1
Understand the context: The genetic code is composed of codons, which are sequences of three nucleotides that correspond to specific amino acids. The experiment by Khorana used a synthetic mRNA with repeating trinucleotide sequences (UUG) to investigate how these codons are translated into amino acids.
Recognize the significance of repeating trinucleotides: When the mRNA contains repeating sequences like UUG, the ribosome reads the sequence in sets of three nucleotides (triplets). This ensures that the genetic code is interpreted in a consistent manner during translation.
Analyze the experimental outcome: The translation of the synthetic mRNA would produce a polypeptide with a repeating pattern of amino acids. For example, UUG could code for one amino acid, and the next UUG triplet would code for the same or a different amino acid, depending on the genetic code.
Connect the results to the triplet nature of the genetic code: The experiment confirms that the genetic code operates in triplets because the repeating trinucleotide sequence (UUG) leads to a predictable and repeating pattern of amino acids in the resulting polypeptide. If the code were not triplet-based, the translation would not produce such a regular pattern.
Conclude the importance of the experiment: This experiment provides strong evidence that the genetic code is read in sets of three nucleotides (triplets), reinforcing the understanding of codon-based translation and the triplet nature of the genetic code.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Triplet Nature of the Genetic Code
The genetic code is composed of nucleotide sequences that are read in groups of three, known as codons. Each codon corresponds to a specific amino acid or a stop signal during protein synthesis. This triplet nature is fundamental to how genetic information is translated into proteins, as it allows for 64 possible combinations from the four nucleotides, accommodating the 20 standard amino acids.
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Synthetic mRNA and Translation
Synthetic mRNA is artificially created RNA that can be designed to contain specific sequences of nucleotides. In the experiment by Khorana, the synthetic mRNA with repeated UUG codons was used to study how ribosomes translate these sequences into proteins. This process demonstrates how the sequence of nucleotides in mRNA dictates the sequence of amino acids in a protein, thereby confirming the triplet nature of the genetic code.
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Experimental Confirmation in Genetics
Experimental confirmation in genetics involves conducting controlled experiments to validate hypotheses about genetic mechanisms. Khorana's experiment provided empirical evidence for the triplet nature of the genetic code by showing that specific sequences of mRNA lead to predictable and consistent protein synthesis. This type of experimental approach is crucial for establishing the principles of molecular biology and genetics.
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Related Practice
Textbook Question
The following figure contains several examples of the Shine–Dalgarno sequence. Using the seven Shine–Dalgarno sequences from E. coli, determine the consensus sequence and describe its location relative to the start codon.
Textbook Question
Har Gobind Khorana and his colleagues performed numerous experiments translating synthetic mRNAs. In one experiment, an mRNA molecule with a repeating UG dinucleotide sequence was assembled and translated.
If the genetic code were overlapping rather than nonoverlapping, how would the result of this experiment be different?
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Textbook Question
An experiment by Khorana and his colleagues translated a synthetic mRNA containing repeats of the trinucelotide UUG.
What is the result obtained from each reading frame?
Textbook Question
The human β-globin polypeptide contains 146 amino acids. How many mRNA nucleotides are required to encode this polypeptide?
Textbook Question
The mature mRNA transcribed from the human β-globin gene is considerably longer than the sequence needed to encode the 146–amino acid polypeptide. Give the names of three sequences located on the mature β-globin mRNA but not translated.