Concept explainers
HOW DO WE KNOW?
In this chapter, we focused on the genetic code and the transcription of genetic information stored in DNA into complementary RNA molecules. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:
(a) How did we determine the compositions of codons encoding specific amino acids?
(b) How were the specific sequences of triplet codes determined experimentally?
(c) How were the experimentally derived triplet codon assignments verified in studies using bacteriophage MS2?
(d) How do we know that mRNA exists and serves as an intermediate between information encoded in DNA and its concomitant gene product?
(e) How do we know that the initial transcript of a eukaryotic gene contains noncoding sequences that must be removed before accurate translation into proteins can occur?
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Essentials of Genetics Plus Mastering Genetics with eText -- Access Card Package (9th Edition) (Klug et al. Genetics Series)
- As 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 informationwas acquired. From the explanations given in the chapter,what answers would you propose to the following fundamentalquestion What experimental information verifies that certain codonsin mRNA specify chain termination during translation?arrow_forwardIt is conceivable for codons encoding a single amino acid to share the first two bases while differing in the third. Why does this experimental finding support the idea of wobble?arrow_forwardSuppose the codon sequence AUGACCCGGCUACUG has a single base pair mutation to AUGACCCGGUUACUG. If the old protein sequence was Met-Thr-Arg-Leu-Leu, what will be the new sequence encoded by the mutant gene?arrow_forward
- As 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 informationwas acquired. From the explanations given in the chapter,what answers would you propose to the following fundamentalquestion What experimentally derived information led to Holley’sproposal of the two-dimensional cloverleaf model of tRNA?arrow_forwardThe amino acid glycine is encoded by four codons: GGA, GGC, GGG, and GGU. Which of the following statements correctly explains this fact? The glycine anticodon contains the sequence CC, but the 5' base of the anticodon can pair nonspecifically with the 3' base of the codon. The glycine anticodon contains the sequence CC, but the 3' base of the anticodon can pair nonspecifically with the 5' base of the codon. Glycine tRNA has four anticodons, and the appropriate anticodon specifically pairs with the correct codon. There are four tRNAs for glycine, each of which has an anticodon that specifically pairs with the correct codon. all of the abovearrow_forwardWhat is an Okazaki fragment, and how are they later “glued” together? What are the types and major functions for each type of RNA? Define transcription and translation. Which process occurs first to make protein from DNA? In what direction does a polymerase move when synthesizing a strand of mRNA? What mRNA sequence is synthesized from a section of DNA that is 3’-TTGACCT-5’?arrow_forward
- If the gene undergoing protein synthesis consists of 24 bases, how many codons does that result in? How many amino acids will the protein consist of?arrow_forwardWhy did geneticists believe, even before direct experimental evidence was obtained, that the genetic code would turn out to be composed of triplet sequences and be non-overlapping?Experimentally, how were these suppositions shown to be correct?arrow_forwardWhat is meant by the statement “The genetic code is universal”? What is the significance of this finding?arrow_forward
- Suppose that codons consisted of 4 nucleotides instead of 3 and that there were only 2 different bases. How many amino acids could be encoded by this variant of the genetic code?arrow_forwardWhat experimental evidence provided the initial insights into the compositions of codons encoding specific amino acids?arrow_forwardWhat is the concept of universality of the genetic code? What are the exceptions to this universality?arrow_forward
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