Characterisation of mutant strainThe mutant strain cdc9--50 was isolated from wild-type S. pombe (972h.. obtained from U. Leupold,Bern) after nitrosoguanidine mutagenesis (P. Nurse and B. Carter, un- published). When grown at 35oc, cells of strain cdc9-50 divide at ahout half the volume of wild-type cells at that temperature(Tahle \). The mutant phenotype is tempera- ture-enhanced since at 25 oc cdc9-50 divides at a cellvolume only 15'X. smaller than wild type (Table I). These differences are also reflected in the RNAand protein con- tent per cell in exponentially growing cultures of the two strains at the twotemperaiures (Table I). Thus cdc9-50 divides at both a lower cell colume and a reduced macro-molecular content compared with wild type. In spite of these differences cdc9-50 has a similargeneration time to wild type at both 25 "C and 35 oc (Table 1).The mutant phenotype of reduced cell size at division segregated 2:2 in all of 27 asci dissected froma wild-type 975 h+ x cdc9- 50h- cross (P. Thuriaux, personal communica- tion), demonstrating that itis caused by a mutation in a single nuclear gene.Table 1 Characteristics of wild type and mutant at 25 C and 35 CCell volume atcell division(µm³)MeanCell volume atnuclear division(um³)MeanGrowth temperature(°C)Macromolecularcontent per cellStrainGeneration time(min)s.d.s.d.ProteinRNA(pg per cell) (pgper cell)Wild-type9722281421291499.16.41211398.49.012.414.12.542.9035Mutantcde9-5023213810972.78.87.898.060.47.98.49.661.162.261.541.Why did they suspect it was caused by a single gene mutation?

Name: Characterisation of mutant strainThe mutant strain cdc9--50 was isola
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Description: Characterisation of mutant strainThe mutant strain cdc9--50 was isolated from wild-type S. pombe (972h.. obtained from U. Leupold,Bern) after nitrosoguanidine mutagenesis (P. Nurse and B. Carter, un- published). When grown at 35oc, cells of strain c

Asci are the cells that bear sexual spores. They are produced when two yeast haploid strains with…

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Strain Wild-type 972 Mutant ede9-50 Growth temperature (°C) 25 35 Table 1 Characteristics of wild type and mutant at 25 C and 35 °C Cell volume at cell division Cell volume at nuclear division (μm³) (μm³) Mean Mean s.d. 25 35 Generation time (min) 228 142 232 138 129 149 109 72.7 s.d. 9.1 6.4 8.8 7.8 121 139 98.0 60.4 1. Why did they suspect it was caused by a single gene mutation? 8.4 9.0 7.9 8.4 Macromolecular content per cell Protein RNA (pg percell) (pg percell) 12.4 14.1 9.66 7.16 2.54 2.90 2.26 1.54

Strain Wild-type 972 Mutant ede9-50 Growth temperature (°C) 25 35 Table 1 Characteristics of wild type and mutant at 25 C and 35 °C Cell volume at cell division Cell volume at nuclear division (μm³) (μm³) Mean Mean s.d. 25 35 Generation time (min) 228 142 232 138 129 149 109 72.7 s.d. 9.1 6.4 8.8 7.8 121 139 98.0 60.4 1. Why did they suspect it was caused by a single gene mutation? 8.4 9.0 7.9 8.4 Macromolecular content per cell Protein RNA (pg percell) (pg percell) 12.4 14.1 9.66 7.16 2.54 2.90 2.26 1.54

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter28: Dna Metabolism: Replication, Recombination, And Repair

Section: Chapter Questions

Problem 16P: Helicase Unwinding of the E. coli Chromosome Hexameric helicases, such as DnaB, the MCM proteins,...

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To determine the reproducibility of mutation fre-quency measurements, you do the following experiment.You inoculate each of 10 cultures with a single E. coli bac-terium, allow the cultures to grow until each contains 106cells, and then measure the number of cells in each culturethat carry a mutation in your gene of interest. You were sosurprised by the initial results that you repeated the experi-ment to confirm them. Both sets of results display the sameextreme variability, as shown in Table Q5–1. Assuming thatthe rate of mutation is constant, why do you suppose thereis so much variation in the frequencies of mutant cells indifferent cultures?
Robert Bost and Richard Cribbs studied a strain of E. coli (araB14)that possessed a nonsense mutation in the structural gene that encodes Lribulokinase,an enzyme that allows the bacteria to metabolize the sugararabinose (R. Bost and R. Cribbs. 1969. Genetics 62:1–8). From thearaB14 strain, they isolated some bacteria that possessed mutations thatcaused them to revert back to the wild type. Genetic analysis of theserevertants showed that they possessed two different suppressormutations. One suppressor mutation (R1) was linked to the originalmutation in L-ribulokinase and probably occurred at the same locus. Byitself, this mutation allowed the production of L-ribulokinase, but theenzyme produced was not as effective in metabolizing arabinose as theenzyme encoded by the wild-type allele. The second suppressormutation (SuB) was not linked to the original mutation. In conjunctionwith the R1 mutation, SuB allowed the production of L-ribulokinase, butSuB by itself was not able to suppress the…
The human genome contains approximately 106 copies of an Alusequence, one of the best-studied classes of short interspersedelements (SINEs), per haploid genome. Individual Alus share a282-nucleotide consensus sequence followed by a 3'-adeninerichtail region. Given that there are approximately 3 * 109bp per human haploid genome, about how many base pairs arespaced between each Alu sequence?
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Price et al. [(1999). J. Bacteriol. 181:2358–2362] conducteda genetic study of the toxin transport protein (PA) of Bacillusanthracis, the bacterium that causes anthrax in humans. Withinthe 2294-nucleotide gene in 26 strains they identified five pointmutations—two missense and three synonyms—among differentisolates. Necropsy samples from an anthrax outbreak in 1979revealed a novel missense mutation and five unique nucleotidechanges among ten victims. The authors concluded that thesedata indicate little or no horizontal transfer between differentB. anthracis strains. Question: Which types of nucleotide changes (missense or synonyms)cause amino acid changes?
Price et al. [(1999). J. Bacteriol. 181:2358–2362] conducteda genetic study of the toxin transport protein (PA) of Bacillusanthracis, the bacterium that causes anthrax in humans. Withinthe 2294-nucleotide gene in 26 strains they identified five pointmutations—two missense and three synonyms—among differentisolates. Necropsy samples from an anthrax outbreak in 1979revealed a novel missense mutation and five unique nucleotidechanges among ten victims. The authors concluded that thesedata indicate little or no horizontal transfer between differentB. anthracis strains. Question: On what basis did the authors conclude that evidence ofhorizontal transfer is absent from their data?
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The entire genome of the yeast Saccharomyces cerevisiaehas been sequenced. This sequencing has led to the identification of all the open reading frames (ORFs, gene-sizesequences with appropriate translational initiation andtermination signals) in the genome. Some of these ORFsare previously known genes with established functions;however, the remainder are unassigned reading frames(URFs). To deduce the possible functions of the URFs,they are being systematically, one at a time, convertedinto null alleles by in vitro knockout techniques. The results are as follows:15 percent are lethal when knocked out.25 percent show some mutant phenotype (alteredmorphology, altered nutrition, and so forth).60 percent show no detectable mutant phenotype at alland resemble wild type.Explain the possible molecular-genetic basis of thesethree mutant categories, inventing examples wherepossible.
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Robert Bost and Richard Cribbs studied a strain of E. coli (araB14) that possessed a nonsense mutation in the structural gene that encodes Lribulokinase, an enzyme that allows the bacteria to metabolize the sugar arabinose (R. Bost and R. Cribbs. 1969. Genetics 62:1–8). From the araB14 strain, they isolated some bacteria that possessed mutations that caused them to revert back to the wild type. Genetic analysis of these revertants showed that they possessed two different suppressor mutations. One suppressor mutation (R1) was linked to the original mutation in L-ribulokinase and probably occurred at the same locus. By itself, this mutation allowed the production of L-ribulokinase, but the enzyme produced was not as effective in metabolizing arabinose as the enzyme encoded by the wild-type allele. The second suppressor mutation (SuB) was not linked to the original mutation. In conjunction with the R1 mutation, SuB allowed the production of L-ribulokinase, but SuB by itself was not able…