Biology
12th Edition
ISBN: 9781260494570
Author: Raven, Peter
Publisher: MCGRAW-HILL HIGHER EDUCATION
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Chapter 16, Problem 1S
You have isolated a series of mutants affecting regulation of the lac operon. All of these are constitutive, that is, they express the lac operon all the time. You also have both mutant and wild-type alleles for each mutant in all combinations, and on F′ plasmids, which can be introduced into cells to make the cell diploid for the relevant genes. How would you use these tools to determine which mutants affect DNA binding sites on DNA, and which affect proteins that bind to DNA?
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Suppose you have six strains of E. coli. One is wildtype, and each of the other five has a single one of thefollowing mutations: lacZ−, lacY−, lacI−, oc, andlacIS. For each of these six strains, describe thephenotype you would observe using the following assays. [Notes: (1) IPTG is a colorless synthetic molecule that acts as an inducer of lac operon expressionbut cannot serve as a carbon source for bacterialgrowth because it cannot be cleaved byβ-galactosidase; (2) X-gal cannot serve as a carbonsource for growth; (3) E. coli requires active lactosepermease (the product of lacY) to allow lactose,X-gal, or IPTG into the cells.] Colony color in medium containing glycerol as theonly carbon source and X-gal, but no IPTG.d. Colony color in medium containing high levels ofglucose as the only carbon source, X-gal, andIPTG.e. Colony color in medium containing high levels ofglucose as the only carbon source and X-gal, butno IPTG
Strain ROFL4 has a premature stop mutation in the lacZ gene, resulting in a nonfunctional b-galactosidase. Otherwise all other parts of the operon are functional.
Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lac operon in the resulting partial diploid. (may need more than one)
(a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restored.
The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).
The possible answers indicate with a ʺ+ʺ or a ʺ-ʺ whether β-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)Genotype F: I+ Oc Z-/ Fʹ I- O+ Z+
KEY:I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)
Chapter 16 Solutions
Biology
Ch. 16.1 - Prob. 1LOCh. 16.1 - Prob. 2LOCh. 16.1 - Prob. 3LOCh. 16.2 - Explain how proteins can interact with base-pairs...Ch. 16.2 - Prob. 2LOCh. 16.3 - Prob. 1LOCh. 16.3 - Prob. 2LOCh. 16.3 - Explain control of gene expression in the trp...Ch. 16.4 - Prob. 1LOCh. 16.4 - Prob. 2LO
Ch. 16.4 - Prob. 3LOCh. 16.5 - Describe at least two kinds of epigenetic mark.Ch. 16.5 - Explain the function of chromatin-remodeling...Ch. 16.6 - Prob. 1LOCh. 16.6 - Prob. 2LOCh. 16.7 - Prob. 1LOCh. 16.7 - Prob. 2LOCh. 16 - Prob. 1DACh. 16 - What advantage might a bacterium gain by linking...Ch. 16 - Prob. 2IQCh. 16 - Prob. 3IQCh. 16 - In prokaryotes, control of gene expression usually...Ch. 16 - Prob. 2UCh. 16 - Prob. 3UCh. 16 - The lac operon is controlled by two main proteins....Ch. 16 - In eukaryotes, binding of RNA polymerase to a...Ch. 16 - In eukaryotes, the regulation of gene expression...Ch. 16 - In the trp operon, the repressor binds to DNA a....Ch. 16 - Prob. 1ACh. 16 - Specific transcription factors in eukaryotes...Ch. 16 - Repression in the trp operon and induction in the...Ch. 16 - Regulation by small RNAs and alternative splicing...Ch. 16 - Eukaryotic mRNAs differ from prokaryotic mRNAs in...Ch. 16 - In the cell cycle, cyclin proteins are produced in...Ch. 16 - A mechanism of control in E. coli not discussed in...Ch. 16 - You have isolated a series of mutants affecting...Ch. 16 - Examples of positive and negative control of...Ch. 16 - What forms of eukaryotic control of gene...Ch. 16 - The number and type of proteins found in a cell...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- The map of the lac operon is shown below. Consider the following examples that include both haploids and partial diploids and explain in each scenario whether the repressor can bind and regulate expression and whether or not the lac operon is expressed. For partial diploids the plasmid is indicated by the F’. I+ O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ I+ Oc Z+ Y+arrow_forwardA number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the highest beta-galactosidase enzyme activity, when grown in the lactose medium. CAP It P+ O`Z+ CAP+ I P+ O+ Zt CAP+ It P- O+ Z+ CAP+ It P+ 0+ Zarrow_forwardParts A-C show the genotypes for partial diploid strains of the lac operon. Gene names have been simplified (ie, LacZ is shown as Z), with alleles shown as standard notations. There are two copies of the operon, one line is the copy in the genome and the other line is on a plasmid. In the blanks, indicate the following based on regulation of the structural gene in the header, choose "functional' if you expect that any amount of normal enzyme will be made, "nonfunctional" if you expect that transcription occurs but the enzyme is mutated, or "no transcription if the structural gene is not transcribed. Assume glucose is absent. LacY Enzyme Activity Genotype of Strain Absence of allolactose I-P+O+Z+Y+ I+P+ O° Z-Y- 1+ P+ OF Z+Y- PP+O+Z-Y+ 1-P+O+Z+Y- I+P-O+Z-Y+ Presence of allolactosearrow_forward
- The streptolysin S toxin made by S. pyogenes is encoded by a 9-gene operon, sagABCDEFGHI. Thinking about what a 3-line diagram would look like for this operon, answer the following questions. Write numeric answers only. For example, if your answer is 6 promoters, write only 6. 1) How many promoters control the expression of these genes? 2) How many locations does RNA Polymerase bind to get full expression of these genes? 3) How many ribosome binding sites are needed for full protein expression? 4) How many start codons will be needed for full protein expression? 5) How many mRNA strands will be produced with full operon expression? 6) How many proteins will be produced with full protein expression? 1arrow_forwardA number of mutations affect the expression of the lac operon in E. coli. Consider each genotype below and complete the table using “+” to indicate that the gene is expressed, and “−” to indicate that gene is not expressed.arrow_forwardA number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the highest beta-galactosidase enzyme activity, when grown in the lactose medium. O CAP+ r* p* o* z O CAP* I P* o* z* O CAP* r* P O* z* O CAP I P* O z*arrow_forward
- Given the following genotypes, explain, by answering the questions in each number, how the mutation (identified by a (-) superscript) will affect E. coli grown in lactose medium. Will there be a complete set ofgene products? (Yes/No) Will the lac operon be turnedon/off? Will the cell survive? (Yes/No) a. i + p + o + z - y + b. i + p - o + z + y + c. i + p + o - z + y +arrow_forwardThe genotypes of five merozygote bacteria are shown below. In each set, the genotype of the lac operon on the chromosome is on the left side of the slash () and the genotype of the lac operon on the F' plasmid is on the right side of the slash. Which of the merozygote bacteria listed below would be able to make high quantities of B-galactosidase in the absence of lactose? Mark all the answers that are correct. O i p*o°z¯ y*A*/F'I$ p*oʻz*y*A* I* p* o*Z¯YA*/F'T P*O*z*y* A* I* P* o*z*Y* A* /F'T P*O*z*y* A* O 1* p*o*z° YA*/F'T P*o°z*y*A* 1S p*0°2¯Y¯AZET P*O*Z*Y*A*arrow_forwardStrain X-23 has a mutation in the lacI gene resulting in a lacI protein that cannot bind DNA. Otherwise all other parts of the operon are functional. Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lacoperon in the resulting partial diploid. (may need more than one) (a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restoredarrow_forward
- Examine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Promoter || Operator genC genB gen operon Regulator genAarrow_forwardA haploid E. coli cell has the genotype I ¯ P+ O+ Z+ Y ¯ where the I ¯ indicates that the repressor protein cannot bind to the operator due to a mutation. Which of the following statements about cells with this lac operon genotype are correct? I ¯ P+ O+ Z+ Y ¯ Select all that apply. β-galactosidase will be transcribed constitutively. The cells are able to import lactose across the cell membrane. The cells are lac+ and are able to grow on a medium with lactose but no glucose. RNA polymerase can bind to the promoter.arrow_forwardIf a wild-type (normal, NOTmutated) E. coli strain is grown in a medium: a. without lactose or glucose, how many proteins (and which ones) are bound to the lac operon? b. Without lactose, but with glucose, how many proteins (and which ones) are bound to the lac operon??arrow_forward
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