Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 8, Problem 58P
Canavanine is an amino acid similar to arginine (see accompanying figure) that is normally synthesized by some plants. Usually, in plants or animals that don’t make canavanine, arginine aminoacyl-tRNA synthetase cannot distinguish between canavanine and arginine, and tRNA can be charged with canavanine. Incorporation of canavanine in proteins in place of arginine can cause misfolding and destroys protein structure and function.
| a. | Can you think of a reason why a plant might have evolved the ability to make canavanine? |
| b. | How do you suppose plants that make canavanine escape its toxicity? |
| c. | A particular vining legume called Dioclea megacarpa makes canavanine and yet still has a single insect predator, a beetle, Caryedes brasiliensis. The beetle lays its eggs on the ripe fruit of the vine, and after hatching, the beetle larvae live in the fruit until they mature into adults. How do you suppose that the beetle evades canavanine toxicity? |
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The charging of a tRNA with an amino acid can be represented by the following equation:amino acid + tRNA + ATP → aminoacyl-tRNA + AMP + PPI where PPI is pyrophosphate (see figure 3–40). in the aminoacyl-tRNA, the amino acid and tRNA are linked with a high-energy covalent bond; a large portion of the energy derived from the hydrolysis of ATP is thus stored in this bond and is available to drive peptide bond formation at the later stages of protein synthesis. the free-energy change of the charging reaction shown in the equation is close to zero and therefore would not be expected to favor attachment of the amino acid to tRNA. Can you suggest a further step that could drive the reaction to completion?
Three E. coli tRNA molecules with the anticodon sequences CGG, OGG , and UGG are charged with the same amino acid. What is the amino acid ?
In bacteria, researchers have isolated strains that carry mutations within tRNA genes. These mutations can change the sequence of the anticodon. For example, a normal tRNATrp gene encodes a tRNA with the anticodon 3′–ACC–5′. A mutation can change this sequence to 3′–CCC–5′. When this mutation occurs, the tRNA still carries a tryptophan at its 3′ acceptor stem, even though the anticodon sequence has been altered.
A. How would this mutation affect the synthesis of polypeptides within the bacterium?
B. What does this mutation tell you about the recognition between tryptophanyl-tRNA synthetase and tRNATrp? Does the enzyme primarily recognize the anticodon or not?
Chapter 8 Solutions
Genetics: From Genes to Genomes
Ch. 8 - For each of the terms in the left column, choose...Ch. 8 - Match the hypothesis from the left column to the...Ch. 8 - How would the artificial mRNA 5GUGUGUGU . . . 3 be...Ch. 8 - An example of a portion of the T4 rIIB gene in...Ch. 8 - Consider Crick and Brenners experiments in Fig....Ch. 8 - The HbSsickle-cell allele of the human -globin...Ch. 8 - The following diagram describes the mRNA sequence...Ch. 8 - The amino acid sequence of part of a protein has...Ch. 8 - The results shown in Fig. 8.5 may have struck you...Ch. 8 - Identify all the amino acid-specifying codons in...
Ch. 8 - Before the technology existed to synthesize RNA...Ch. 8 - A particular protein has the amino acid sequence...Ch. 8 - How many possible open reading frames frames...Ch. 8 - Prob. 14PCh. 8 - Charles Yanofsky isolated many different trpA-...Ch. 8 - The sequence of a segment of mRNA, beginning with...Ch. 8 - You identify a proflavin-generated allele of a...Ch. 8 - Using recombinant DNA techniques which will be...Ch. 8 - Describe the steps in transcription that require...Ch. 8 - Chapters 6 and 7 explained that mistakes made by...Ch. 8 - The coding sequence for gene F is read from left...Ch. 8 - If you mixed the mRNA of a human gene with the...Ch. 8 - Prob. 23PCh. 8 - The Drosophila gene Dscam1 encodes proteins on the...Ch. 8 - Describe the steps in translation that require...Ch. 8 - Locate as accurately as possible the listed items...Ch. 8 - Concerning the figure for Problem 26: a. Which...Ch. 8 - a. Can a tRNA exist that has the anticodon...Ch. 8 - For parts a and b of Problem 28, consider the DNA...Ch. 8 - Remembering that the wobble base of the tRNA is...Ch. 8 - Prob. 31PCh. 8 - The yeast gene encoding a protein found in the...Ch. 8 - The sequence of a complete eukaryotic gene...Ch. 8 - Arrange the following list of eukaryotic gene...Ch. 8 - Prob. 35PCh. 8 - The human gene for 2 lens crystallin has the...Ch. 8 - In prokaryotes, a search for genes in a DNA...Ch. 8 - a. The genetic code table shown in Fig. 8.2...Ch. 8 - a. Very few if any eukaryotic genes contain tracts...Ch. 8 - Explain how differences in the initiation of...Ch. 8 - Do you think each of the following types of...Ch. 8 - Null mutations are valuable genetic resources...Ch. 8 - The following is a list of mutations that have...Ch. 8 - Considering further the mutations described in...Ch. 8 - Adermatoglyphia described previously in Problem 18...Ch. 8 - Prob. 46PCh. 8 - You learned in Problem 21 in Chapter 7 that the...Ch. 8 - When 1 million cells of a culture of haploid yeast...Ch. 8 - Why is a nonsense suppressor tRNATyr, even though...Ch. 8 - A mutant B. adonis bacterium has a nonsense...Ch. 8 - You are studying mutations in a bacterial gene...Ch. 8 - Another class of suppressor mutations, not...Ch. 8 - Yet another class of suppressor mutations not...Ch. 8 - At least one nonsense suppressing tRNA is known...Ch. 8 - An investigator was interested in studying UAG...Ch. 8 - Prob. 56PCh. 8 - In certain bacterial species, pyrrolysine Pyl,...Ch. 8 - Canavanine is an amino acid similar to arginine...
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- A mutant E. coli strain is found with a mutation affecting some of its tRNA(Cys). The wild type normally produces a tRNA that recognizes the codon 5’ UGC 3’, and is charged with the amino acid Cysteine (Cys) (its notation is tRNA(Cys)). The mutant tRNA is still charged with Cysteine, but the mutation is in its anticodon that now has the sequence 5’- UCA-3’. How will some of the proteins produced in these E. coli cells be different from the proteins produced in the wild type cellsarrow_forwardOrnithine is structurally similar to lysine except ornithine’s side chain is one methylene group shorter than that of lysine. Attempts to chemically synthesize and isolate ornithinyl-tRNA proved unsuccessful. Propose a mechanistic explanation. (Hint: Six-membered rings are more stable than sevenmembered rings.)arrow_forwardGiven the following mRNA and amino acids, construct a polypeptide from this tRNA strand. tRNA UAA CCA UUA UAA mRNA Amino Acids AUU = isoleucine AAU = asparginine GGU = glycine GUC = valine GAG = glutamic acidarrow_forward
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