Concept explainers
To analyze:
An inducible operon of bacteria has three genes R, T, and S – same as lactose operon. These genes play a role in the regulation of transcription. These genes can be operator gene, regulatory gene, and structural gene (codes for structural enzyme). In the question, a table is provided in which
Introduction:
A unit of DNA that has a group of genes controlled by a single promoter is termed as an operon. The operon possesses different regions (operator, promoter and structural genes); each region has a different role. Operator region is a short region of operon that controls transcription of genes by interacting with regulatory proteins. Regulatory proteins include proteins that act as transcription factor and facilitate the synthesis of protein in bacteria. Any protein which has its impact on the region of operon (DNA), which is transcribed in the transcription, is a regulatory protein.
The gene which codes for the protein other than the regulatory protein is termed as the structural gene. The product of structural genes is structural protein and enzymes.
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Genetic Analysis: An Integrated Approach (3rd Edition)
- Listed in parts a through g are some mutations that were found in the 5′ UTR of the trp operon of E. coli. What will the most likely effect of each of these mutations be on the transcription of the trp structural genes? a. A mutation that prevents the binding of the ribosome to the 5′ end of the mRNA 5′ UTR b. A mutation that changes the Trp codons in region 1 of the mRNA 5′ UTR into codons for alanine c. A mutation that creates a stop codon early in region 1 of the mRNA 5′ UTR d. Deletions in region 2 of the mRNA 5′ UTR e. Deletions in region 3 of the mRNA 5′ UTR f. Deletions in region 4 of the mRNA 5′ UTR g. Deletion of the string of adenine nucleotides that follows region 4 in the 5′ UTRarrow_forwardIn lac operon, both gene A and gene B undergo a transcription process. Gene B can only undergo transcription in the presence of lactose and in the absence of glucose. The product of gene A is often altered by an inducer. Which of the following is true about genes A and B? Select one: a. Gene A= structural gene; Gene B= regulatory gene b. Gene A= regulatory gene; Gene B= structural gene c. Gene A= promoter gene; Gene B= operator gene d. Gene A= lacZ gene; Gene B= promoter genearrow_forward. Listed in parts a through g are some mutations that were found in the 5′ UTR of the trp operon of E. coli. What will the most likely effect of each of these mutations be on the transcription of the trp structural genes? Q. A mutation that changes the Trp codons in region 1 of the mRNA 5′ UTR into codons for alaninearrow_forward
- 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?arrow_forwardGiven the Table below concerning the lac operon, match the letter with what would be occurring for each scenario. Repressor is bound to the operator, cAMP complex is bound and transcription is prevented. Allolactose is bound to the repressor, cAMP complex is bound, and transcription is prevalent. Allolactose is bound to the repressor, cAMP complex is not assembled, and transcription is slow Repressor is bound to the operator, cAMP complex is not assembled, and transcription is prevented.arrow_forwardWhat 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.arrow_forward
- If glucose levels in the cell are high and 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?arrow_forwardYou 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?arrow_forwardWhat does the lac operon consist of? How is the operator switch turned on and off in the expression of genes in this operon? Explain.arrow_forward
- One of the main lessons of this chapter is that several bacterial genes are often transcribed from a single promoter into a large multigene (polycistronic) transcript. The region of DNA containing the set of genes that are cotranscribed, along with all of the regulatory elements that control the expression of these genes, is called an operon. a. Which of the mechanisms in the following list (i-vi) could explain differences in the levels of the mRNAs for different operons? Different promoters might have different DNA sequences Different promoters might be recognized by different types of RNA polymerase The secondary structures of mRNAs might differ which will influence the rate at which they are degraded by ribonucleases. In an operon, some genes are farther away from the promoter than other genes The translational initiation sequences at the beginning of different open reading frames in an operon might result in different efficiencies of translation Proteins encoded by different genes…arrow_forwardMutations 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. If the promoter for the lac operon is TATGTT, would the following be uppromoters or downpromoters?A. TATGTT to TATATTB. TATGTT to TTTGTTC. TATGTT to TATGATarrow_forwardMutations 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 TATGATarrow_forward
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