Textbook Question
Describe the gene and protein defects in phenylketonuria (PKU). How are these defects connected to disease symptoms?
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 4
Outline the events that occur during initiation of translation in E. coli.
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Identify the Shine-Dalgarno sequence on the mRNA, which is a purine-rich region located upstream of the start codon (AUG). This sequence helps the ribosome recognize and bind to the mRNA.
The small ribosomal subunit (30S) binds to the mRNA at the Shine-Dalgarno sequence with the help of initiation factors (IFs), such as IF-1, IF-2, and IF-3.
The initiator tRNA, charged with N-formylmethionine (fMet-tRNAfMet), pairs with the start codon (AUG) on the mRNA in the P site of the ribosome. This step is facilitated by IF-2, which is bound to GTP.
The large ribosomal subunit (50S) associates with the small subunit to form the complete 70S initiation complex. This step is accompanied by the hydrolysis of GTP to GDP, which is catalyzed by IF-2.
The initiation factors (IF-1, IF-2, and IF-3) are released, leaving the ribosome ready to proceed with the elongation phase of translation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Translation Initiation
Translation initiation is the first step in protein synthesis where the ribosome assembles around the mRNA. In E. coli, this process begins when the small ribosomal subunit binds to the mRNA at the start codon, typically AUG, which codes for methionine. This step is crucial as it sets the reading frame for the ribosome to translate the mRNA into a polypeptide chain.
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Translation initiation
Shine-Dalgarno Sequence
The Shine-Dalgarno sequence is a ribosomal binding site in bacterial mRNA that is essential for the initiation of translation. It is located upstream of the start codon and helps align the ribosome with the mRNA by base-pairing with a complementary sequence on the 16S rRNA of the small ribosomal subunit. This interaction ensures that translation begins at the correct site.
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Initiation Factors
Initiation factors are proteins that facilitate the assembly of the ribosome and the initiation of translation. In E. coli, key initiation factors such as IF1, IF2, and IF3 play roles in stabilizing the binding of the ribosomal subunits to the mRNA and the initiator tRNA. These factors are essential for ensuring the accuracy and efficiency of the translation initiation process.
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Related Practice
Textbook Question
In the experiments that deciphered the genetic code, many different synthetic mRNA sequences were tested.
What result was obtained for synthetic mRNAs containing AG repeats, that is, AGAGAGAG...?
Textbook Question
In the experiments that deciphered the genetic code, many different synthetic mRNA sequences were tested.
Predict the results of experiments examining GCUA repeats.
Textbook Question
Several lines of experimental evidence pointed to a triplet genetic code. Identify three pieces of information that supported the triplet hypothesis of genetic code structure.
Textbook Question
A portion of a DNA template strand has the base sequence
5′-...ACGCGATGCGTGATGTATAGAGCT...-3′
Identify the sequence and polarity of the mRNA transcribed from this fragmentary template-strand sequence.
Textbook Question
A portion of a DNA template strand has the base sequence
5′-...ACGCGATGCGTGATGTATAGAGCT...-3′
Assume the mRNA is written in the correct reading frame. Determine the amino acid sequence encoded by this fragment. Identify the N- and C-terminal directions of the polypeptide.