Biological Science (7th Edition)
7th Edition
ISBN: 9780134678320
Author: Scott Freeman, Kim Quillin, Lizabeth Allison, Michael Black, Greg Podgorski, Emily Taylor, Jeff Carmichael
Publisher: PEARSON
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Chapter 18, Problem 8TYU
Summary Introduction
To review:
The effect of the addition of the Isopropyl β-D-1-thiogalactopyranoside (IPTG) to the Escherichia coli growth medium containing no glucose or lactose on lac operon regulation.
Introduction:
The IPTG is a structure quite similar to the lactose molecule. It can be transported by the galactoside permease and is capable of binding to the lac repressor protein. Isopropyl β-D-1-thiogalactopyranoside (IPTG) is a molecule with structure resemblance to lactose. IPTG can be transported into cells by galactoside permease and can bind to the lac repressor protein. However, unlike lactose, IPTG is not broken down by β-galactosidase.
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Students have asked these similar questions
Which of the following lac operon genotypes would allow for functional versions of all the structural enzymes of the lac operon to be expressed constitutively even in the absence of lactose?
Group of answer choices
I+ O+ Z+ Y+ A+
I- O+ Z- Y- A-
I+ OC Z+ Y+ A+
IS O+ Z+ Y+ A+
I+ O+ Z- Y+ A+
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?
1
Give all possible genotypes of a lac operon that produces, or fails to
produce, B-galactosidase and permease under the following conditions.
Do not give partial-diploid genotypes.
Lactose present
B-Galactosidase
Lactose absent
B-Galactosidase
Permease
Permease
a.
b.
C.
d.
e.
f.
g.
+ I + II +
+ + | +I
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- 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. 1. Can strain ROFL4 metabolize lactose if it is present? 2. If lactose is absent, will strain ROFL4 transcribe its lac operon? 3. If lactose is present, will strain ROFL4 transcribe its lac operon?arrow_forwardThe 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_forwardThe diagram below represents the tryptophan operon with the trp leader mRNA transcript enlarged to represent the AUG translation start codon, two consecutive tryptophan amino acid codons (UGGUGG), and 4 regions (1, 2, 3, and 4) that base pair to form different hairpin-loop structures in the MRNA leader region. Suppose a mutant bacteria has region 4 of the trp operon attenuator region mutated so that it cannot base pair normally. Would the bacteria grow in the absence of the amino acid tryptophan? (hint: in order for bacteria to grow in absence of tryptophan it should be able to synthesize its own tryptophan) Lead&r region trpE trpD trpC trpB trpA DNA 5' 3' Transcription trp leader sequence MRNA UGGUGG 1 (tryptophan codons) AUG UUUUUU No There is insutficient information to answer the question. O Yesarrow_forward
- Given the following mutant and conditions, predict the expression of the lacZ gene (no expression, basal level, activate level of expression). A mutant of E. coli has a mutation in the promoter of the lac operon that prevents RNA polymerase from binding. + glucose, - lactose + glucose, + lactose – glucose, + lactosearrow_forwardThe diagram below represents the tryptophan operon with the trp leader mRNA transcript enlarged to represent the AUG translation start codon, two consecutive tryptophan amino acid codons (UGGUGG), and 4 regions (1, 2, 3, and 4) that base pair to form different hairpin-loop structures in the mRNA leader region. Suppose a mutant bacteria has region 3 of the trp operon attenuator region mutated so that it cannot base pair normally. Would the bacteria grow in the absence of the amino acid tryptophan? (hint: in order for bacteria to grow in absence of tryptophan it should be able to synthesize its own tryptophan) Leader region trpE trpD trpC trpB trpA DNA 5' 3' Transcription trp leader sequence MRNA AUG UGGUGG UUUUUU 1 2 3 (tryptophan codons) There is insufficient information to answer the question. Yes No O Oarrow_forwardExplain why inactivation of the O1 sequence of the lac operator almost completely abolishes repression of the lac operon.arrow_forward
- The molecules indicated below can be used experimentally due to their roles in relation to the expression of the lac operon. Drag the listed molecules to their corresponding bin. Reset Help ONPG IPTG X-Gal allolactose Dragable beta-galactosidase cleaves this molecule to form a visible yellow product. beta-galactosidase cleaves this molecule which then dimerizes to form a visible blue product. This molecule induces the transcription of the lac operon by inactivating the lac repressor.arrow_forwardThe diagram below represents a hypothetical operon in the bacterium E. coli. The operon consists of two structural genes (A and B), which code for the enzymes “Aase" and "Base", respectively, and also includes P (promoter) and O (operator) regions as shown. A В When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes "Aase" and "Base" are both synthesized at a 50-fold higher rate than in the absence of X. (X has a molecular weight of about 200.) Which of the following statements is true of the operon described above? The region of the A gene that codes for the carboxyl-terminal amino acid of “Aase" is near the left end of the A gene. The P region contains nucleotide sequences to which the RNA polymerase holoenzyme (including the o subunit) binds specifically but which the core enzyme does not recognize. The addition of X to the growth medium causes a repressor protein to bind tightly to the O region. The mRNA copied from this operon will be covalently…arrow_forwardA theoretical operon (theo) in E. coli contains several structural genes encoding enzymes that are involved sequentially in the biosynthesis of an amino acid. Unlike the lac operon, in which the repressor gene is separate from the operon, the gene encoding the regulator molecule is contained within the theo operon. When the end product (the amino acid) is present, it combines with the regulator molecule, and this complex binds to the operator, repressing the operon. In the absence of the amino acid, the regulatory molecule fails to bind to the operator, and transcription proceeds. Characterize this operon, then consider the following mutations, as well as the situation in which the wild-type gene is present along with the mutantgene in partially diploid cells (F¿):(a) Mutation in the operator region.(b) Mutation in the promoter region.(c) Mutation in the regulator gene.In each case, will the operon be active or inactive in transcription, assuming that the mutation affects the…arrow_forward
- To study the lac operon, you engineer a strain of E coli to have a lac operon in which the lac Z gene is replaced by the gene for green fluorescent protein (GFP). Expression of GFP generates a green color in the cells that can be easily quantitated with a fluorescence microscope. You test the activity of the operon in the absence of the inducer IPTG, the presence of the inducer IPTG and the presence of an antibiotic the completely inhibits RNA polymerase (i.e. no gene expression). You then use this system to test the effects of various mutation on the activity of the operon. Match the following mutations with the activity (A, B or C) you would expect to observe with the mutation. All experiments are done in the presence of IPTG unless otherwise stated.arrow_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_forwardGiven the following mutant and conditions, predict the expression of the lacZ gene (no expression, basal level, activate level of expression). A mutant of E. coli that has a mutation in the operator of the lac operon that prevents the repressor from binding. + glucose, - lactose + glucose, + lactose – glucose, + lactosearrow_forward
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