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- In this chapter, we focused on the translation of mRNA into proteins as well as on protein structure and function. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations in the chapter, what answers would you propose to the following fundamental questions: What experimental information verifies that certain codons in mRNA specify chain termination during translation?
Problem 1
Problem 1a
What experimentally derived information led to Holley's proposal of the two-dimensional cloverleaf model of tRNA?
Problem 1c
How do we know, based on studies of Neurospora nutritional mutations, that one gene specifies one enzyme?
Problem 1d
On what basis have we concluded that proteins are the end products of genetic expression?
Problem 1e
How do we know that the structure of a protein is intimately related to the function of that protein?
- Write a short essay that discusses the role of ribosomes in the process of translation as it relates to these concepts.
Problem 2
Problem 3
Contrast the roles of tRNA and mRNA during translation, and list all enzymes that participate in the transcription and translation process.
Problem 4
Francis Crick proposed the 'adaptor hypothesis' for the function of tRNA. Why did he choose that description?
Problem 5
During translation, what molecule bears the codon? the anticodon?
Problem 6
The α chain of eukaryotic hemoglobin is composed of 141 amino acids. What is the minimum number of nucleotides in an mRNA coding for this polypeptide chain?
Problem 7
Assuming that each nucleotide in an mRNA is 0.34 nm long, how many triplet codes can simultaneously occupy the space in a ribosome that is 20 nm in diameter?
Problem 8
Summarize the steps involved in charging tRNAs with their appropriate amino acids.
Problem 9
To carry out its role, each transfer RNA requires at least four specific recognition sites that must be inherent in its tertiary structure. What are they?
Problem 10
What are isoaccepting tRNAs? Assuming that there are only 20 different aminoacyl tRNA synthetases but 31 different tRNAs, speculate on parameters that might be used to ensure that each charged tRNA has received the correct amino acid.