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Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN: 9780134580999
Author: Elaine N. Marieb, Katja N. Hoehn
Publisher: PEARSON
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
Transcribed Image Text:The lac operon regulates expression of genes required for the breakdown of lactose.
Use the schematic diagram of the lac operon to help you answer the following
questions about the lac operon.
Representation of the Lac operon and upstream
regions in E.coli (not drawn to scale!)
Indicates 1,000s bases
Indicates regions of DNA
lacz
lacz
lacz
gene
gene
gene
....
Lac I promoter
Lac I gene
CRP
lac Z
lac
lac Z
lacY
lacA
binding
promoter
operator
gene
gene
gene
site
When wild-type E. coli are grown in media with high lactose and high glucose, which
of the following statements are true?
RNA polymerase can bind tightly to the lac Z promoter and activate a high level
of transcription
CRP protein is bound to the CRP binding site
There is a basal level of lac Z, Y and A transcription
O RNA polymerase can bind tightly to the lac I promoter and activate a high level
of transcription
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- As diagrammed below, some amino acid biosynthetic operons have stem loop structures in the mRNA. These structures play a role in the regulation of the operon by which of the following mechanisms? Translation stop codon- Attenuator loop. mRNA 5' 3' DNA attenuator trpE O Catabolite repressor protein can bind and prevent the hairpins from forming thus allowing translation to occur. O The leader sequence shown contains codons for the amino acid. When these are low, the ribosome stalls, allowing a hairpin between the two middle regions to form so that the rest of the message can be translated. In the presence of large amounts of the amino acid, the hairpin will wind around the amino acid and prevent further translation. O A repressor protein made of that amino acid will bind to the region and prevent translation when large amounts of the amino acid are present. O The uridine-rich region has codons for that amino acid; when present, this region will be a terminator region. The hairpins allow…arrow_forwardWhat ratoe of NADPH to NADP+ is required to maintain [GSH]=10mM and [GSSH]= 1 mM?arrow_forwardIndicate whether each of the following statements about the lac operon are true or false: Bacteria with a lac phenotype are unable to use lactose because of some defect in expressing the genes A constitutive Lac+ phenotype could mean either that the production of repressor is defective or that the operator sequence is defective The lacl gene is next to, but is not part of, the lac 1. TRUE operon 2. FALSE Bacteria with a lac* phenotype cannot grow on media containing lactose as the only sugar The structural genes of the lac operon are each transcribed as a separate MRNA Expression of the Lac Repressor from the lacl promoter is regulated by lactosearrow_forward
- Need answer and explainarrow_forward1. Draw a diagram of the lac operon. PO I+P+O+Z+Y+ I+P+OcZ+Y- I-P+O+Z+Y+ Lab section (circle): lacz gene lac Y gene lacA gene I+P+O+ZY/IPO+Z+Y- 2. The promoter (P) is the start site of transcription through the binding of RNA polymerase before actual mRNA production. Mutated promoters (P) cannot bind RNA polymerase, so no mRNA is made. In the table below, make predictions about the expression of ß-galactosidase and permease for different partial diploid (F') genotypes. Do this for E. coli growth on two different types of media - one without lactose, and one with. Use a to mark where there is no enzyme produced, and a + to mark where the enzyme is made. The first genotype has all wild-type alleles, and has been filled in as an example. Genotype IPOCZ+Y/I-P+O+Z-Y+ ISP+O+Z+Y/I+P+O+Z*Y* CR 1:00 Lactose absent B-galactosidase Permease R 3:-00 + R 6:30 Lactose present B-galactosidase F 10:00 Permeasearrow_forwardThe 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_forward
- Suppose that E. coli sustains a mutation in its gene for the lac operon repressor making the repressor ineffective. How would this mutation affect the bacterium's ability to catabolize lactose? Would the mutant strain have an advantage over the wild-type strain? Explain your answer. (Minimum 150 words, the document will be checked for plagiarism)arrow_forwardRead the following statements about operons, and mark the FALSE one. O a. Prokaryotes use operons frequently because they are an efficient use of resources O b. The expression levels of the genes in an operon can be regulated individually Genes in an operon are placed next to each other (physically) O d. The genes in an operon share a single promoterarrow_forward4) Suppose you have an E. coli in which the gene that codes for the lac repressor protein has been mutated in such a way that the protein produced can bind to both lactose and DNA (at its specific binding site in the lac operon promoter) simultaneously. What effect, if any, would this have on regulation of expression of the lac operon? Briefly (1 sentence) explain why you would predict the effect or lack of effect this mutation would have.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_forwardFor the wildtype E. coli two sugars influence the level of transcription of the lactose operon. Fill in the table wvith the choices (shown in parenthesis) in each column to show how these two sugars influence gene regulation. Sugars in the growth media: CAMP levels positive regulation negative regulation Relative level of Lac operon transcription (highest, inbetween, lowest) (high or low) оссurs оссurs (yes or no) (yes or no) glucose present; lactose absent glucose present; lactose present glucose absent; lactose presentarrow_forwardAssuming that the level of glucose is low, a mutation in the repressor associated with the lac operon of E. coli which prevents binding of the repressor to lactose should result in_____ Constitutive expression of the lac operon genes ito sagot ko Lack of expression or reduced expression of the lac operon genes under all circumstances Expression of the genes only when lactose is present Expression of the genes only when lactose is absentarrow_forward
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