You have isolated two different mutants (reg1 and reg2) causing constitutive expression of the emu operon (emu1 emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site. Is the DNA-binding protein a positive or negative regulator of gene expression? Explain. To determine which mutant has a defect in the site and which one has a mutation in the binding protein, you decide to do an analysis using F′ plasmids. Assuming you can assay levels of the Emu1 and Emu2 proteins, what results do you predict for the two strains (i and ii; see descriptions below) if reg2 encodes the regulatory protein and reg1 is the regulatory site? Explain. F′ (reg1− reg2+ emu1− emu2+)/reg1+ reg2+ emu1+ emu2− F′ (reg1+ reg2− emu1− emu2+)/reg1+ reg2+ emu1+ emu2−

You have isolated two different mutants (reg1 and reg2) causing constitutive expression of the emu operon (emu1 emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site. Is the DNA-binding protein a positive or negative regulator of gene expression? Explain. To determine which mutant has a defect in the site and which one has a mutation in the binding protein, you decide to do an analysis using F′ plasmids. Assuming you can assay levels of the Emu1 and Emu2 proteins, what results do you predict for the two strains (i and ii; see descriptions below) if reg2 encodes the regulatory protein and reg1 is the regulatory site? Explain. F′ (reg1− reg2+ emu1− emu2+)/reg1+ reg2+ emu1+ emu2− F′ (reg1+ reg2− emu1− emu2+)/reg1+ reg2+ emu1+ emu2−

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Description: You have isolated two different mutants (reg1 and reg2) causing constitutive expression of the emu operon (emu1 emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter10: From Proteins To Phenotypes

Section: Chapter Questions

Problem 21QP: Transcriptional regulators are proteins that bind to promoters (the 5-flanking regions of genes) to...

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You have isolated different mutants (reg1 and reg2) causing constitutive expression of the emu operon (which has genes emu1 and emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site. Is the DNA-binding protein a positive or negative regulator of gene expression?
In the galactose operon of Escherichia coli, a repressor, encoded by the galR gene, binds to an operator site, galo, to regulate the expression of three structural genes, galE, galT, and galK. Expression is induced by the presence of galactose in the media. For each of the strains listed, would the cell show constitutive, inducible, or no expression of each of the structural genes? (Assume that galR−is a loss-of-function mutation.) galR− galo+ galE+ galT+ galK+ galR+ galoc galE+ galT+ galK+ galR− galo+ galE+ galT+ galK−/ galR+ galo+ galE− galT+ galK+ galR− galoc galE+ galT+ galK−/ galR+ galo+ galE− galT+ galK+
You have isolated different mutants (reg1 and reg2) causing constitutive expression of the emu operon (which has genes emu1 and emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site Say you don’t know which mutant has a defect in the site and which one has a mutation in the binding protein. To figure it out, you construct the two partial diploid strains (i and ii below), and you then assay the levels of the Emu1 and Emu2 proteins in these two strains. F’ (reg1- reg2+ emu1- emu2+) / reg1+ reg2+ emu1+ emu2- F’ (reg1+ reg2- emu1- emu2+) / reg1+ reg2+ emu1+ emu2- What proteins do you predict will be expressed for strains i and ii if reg2 encodes the regulatory protein and reg1 is the regulatory site?
What experimental results would indicate that the mutation lacISlacIS is dominant to lacI+lacI+? In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a constitutive state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in an activated state in the presence of lactose. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the absence of the repressor. In lacISlacIS/lacI+lacI+ partial diploids, the lac operon is in a repressed state in the presence of lactose.
In the lac operon (below), how will expression of the genes lacZ and lacy be effect by a mutation in the repressor protein (encoded by lach) that prevents it from binding the operator sequence (lacO) in the absence of lactose? Explain the answer
Suppose you are studying the regulation of a gene involved in the metabolism of two nutrients, Llamasin and Alpacalon, in bacteria. You are trying to determine if these nutrients act as inducers in their operons. The following data were collected from your experiments. Which of these operons is most similar to the lac operon? Explain. Nutrient Levels of nutrient in growth medium Level of transcription of genes in operon Llamasin low high high low Alpacalon low low high high Highlight one in green: Llamasin Alpacalon Explanation:
Mutations in bacterial promoters may increase or decrease the rate of gene transcription. Promoter mutations that increase the transcription rate are termed up-promoter mutations, and those that decrease the transcription rate are termed down-promoter mutations. As shown , the sequence of the −10 site of the promoter for the lac operon is TATGTT. Would you expect the following mutations to be up-promoter or down-promoter mutations? A. TATGTT to TATATT B. TATGTT to TTTGTT C. TATGTT to TATGAT
Under what conditions would you expect to see high levels of expression of the structural genes in the lac operon? Group of answer choices Lactose is absent and glucose is absent Lactose is absent and glucose is present Lactose is present and glucose is present None of these Lactose is present and glucose is absent
How does the binding of the trp corepressor and the lac inducer to their respective repressor proteins alter repressor function and transcription in each case? What if there was a mutation in the operator region of the lac operon and the active repressor could not bind there? How would this affect the cell’s production of β–galactosidase? In general, Histone acetylation makes DNA ___________________, while DNA methylation makes DNA ________________.
The yeast gene SER3, whose product has a role in serine biosynthesis, is repressed during growth in nutrient-rich medium, so little transcription takes place, and little SER3 enzyme is produced, under these conditions. In an investigation of the repression of the SER3 gene, a region of DNA upstream of SER3 was found to be heavily transcribed when SER3 is repressed ). Within this upstream region is a promoter that stimulates the transcription of an RNA molecule called SRG1 RNA (for SER3 regulatory gene 1). This RNA molecule has none of the sequences necessary for translation. Mutations in the promoter for SRG1 result in the disappearance of SRG1 RNA, and these mutations remove the repression of SER3. When RNA polymerase binds to the SRG1 promoter, the polymerase travels downstream, transcribing the SGR1 RNA, and passes through and transcribes the promoter for SER3. This activity leads to the repression of SER3. Propose a possible explanation for how the transcription of SGR1 might…
Suppose you want to study the transcription in vitro of one particular gene in a DNA molecule that contains several genes and promoters. Without adding specific regulatory proteins, how might you stimulate transcription from the gene of interest relative to the transcription of the other genes on your DNA template? To make all of the complexes identical, you would like to arrest all transcriptional events at the same position on the DNA template before isolating the complex. How might you do this?
If glucose is not available, but lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?