Concept explainers
INTERPRET DATA Develop a simple hypothesis that would explain the behavior of each of the following types of mutants in E. coli.
Mutant a: The map position of this mutation is in the trp operon. The mutant cells are constitutive; that is, they produce all the enzymes coded for by the trp operon, even if large amounts of tryptophan are present in the growth medium. Mutant b: The map position of this mutation is in the trp operon. The mutant cells do not produce any enzymes coded for by the trp operon under any conditions. Mutant c: The map position of this mutation is some distance from the trp operon. The mutant cells are constitutive; that is, they produce all the enzymes coded for by the trp operon, even if the growth medium contains large amounts of tryptophan.
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EBK BIOLOGY
- . 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.]a. Growth on medium in which the only carbonsource was lactose.b. Colony color in medium containing glycerol as theonly carbon source, X-gal, and IPTGarrow_forwardYou can determine the regulation of an unknown operon based on descriptions like those in the table below. For each row, choose whether the fact would suggest positive or negative or inducible or repressible regulation and indicate your answer with an X in the column. Only one X should appear in each row. In the presence of the signal, the structural genes are expressed. In the presence of the signal, the structural genes are not expressed. In the absence of the signal, the structural genes are expressed. In the absence of the signal, the structural genes are not expressed. The binding of the regulatory protein to the operon results in structural gene expression. The binding of the regulatory protein to the operon prevents structural gene expression. A mutation in the regulatory protein results in constitutive expression of the structural genes. A mutation in the regulatory protein results in no or low expression of the structural genes. Positive? Negative? Inducible? Repressible?arrow_forwardThe lactose operon in E. coli comprises two structural genes and three regulatory components.a.State the name of each structural gene and describe its function: b.) State the name of each regulatory component and describe its functionarrow_forward
- Analyze the following genotypes of the Lac Operon in E. coli. In each case, determine whether Beta-galactosidase (enzyme that digests lactose) and permease (membrane channel that brings lactose into the cell) would be made in the presence or absence of lactose. For the purpose of this question, ignore glucose levels. Simply select 'YES' if the proteins are made or 'NO' if they are not . (Refer to the Lac Operon diagram for the meaning of the letters in the genotypes. Remember a "plus" superscript indicates normal functioning part of operon or repressor gene, a "minus" indicates loss of function, "OC" means "operator- constitutive", and "IS" means "super-repressor") Absence of Lactose Presence of Lactose Genotype В-gal Permease В -gal Permease IS pt 0 z+ Y-/ I† p+ 0C z¯ y+ It p+ 0C z+ y+/ I* P¯ 0 Z- Y It P 0C Z- Y+/ I¯ p* 0 z+ y It pt o z Y+/ I¯ p+ 0 z+ Yarrow_forwardSupply the words “off" or “on" in the blanks below: In an inducible operon, transcription is normally and must be turned In a repressible operon, transcription is normally and must be turned Briefly describe the overall function of the structural genes in the lac operon. Briefly describe the overall function of the structural genes in the trp operon. For the following descriptions of the bacterial lac operon, determine if lactose is present (P) or absent (A). The repressor is bound to the operator. The repressor is inactive. RNA polymerase transcribes the structural genes. Allolactose is bound to the repressor For the following descriptions of the bacterial trp operon, determine if tryptophan levels are high (H) or low (L). The repressor is bound to the operator. The repressor is inactive. RNA polymerase transcribes the structural genes. Tryptophan is bound to the repressor.arrow_forwardselect all the mutations that could applyarrow_forward
- Which option is true when considering the regulation of cAMP and the Lac operon. If bacteria are in a medium containing low glucose, but suddenly glucose concentration in the medium increases by ten times, then we expect that cAMP...... a) Will increase inside the cell. b) Will not increase inside the cell.arrow_forwardIn the bacterium,Martian coli, it was discovered that the lac operon is positively regulated. Lactose, when present, binds to the regulatory protein A. The protein A-lactose complex then binds to the operator domain 0 and induces synthesis of lacZ+ and lacY+ MRNAS. a) What would be the most common phenotype of o- mutants in terms of lactose utilization? Explain your answer. b) What would be the most common phenotype of A- mutants? Explain your answer.arrow_forwardSuppose 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_forward
- In addition to observing similarities to the lac operon, you also notice that this gene is regulated via attenuation, similar to the trp operon. Based on this similarity to this model operon, you could state that ___________. Group of answer choices If a terminator loop forms in the DNA, the expression of the structural genes is halted. The formation of the terminator hairpin followed by a series of Uracil (UUUUUUU) functions similar to Rho-Independent termination to result in the stopping of transcription. The transcription of a leader sequence affects the translation of the structural genes. Never mind – all of these statements are true! Attenuation will be the primary means of transcriptional regulation, with a repressor used as a back up option.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_forwardConsider the following simple regulatory pathways. Assume the full pathway is shown. A- E- B- F- C- G- D- 1 H- A You identify several null mutations (a complete deletion of the gene). For each mutant (ind with a - sign), determine whether the final product (I, J, K or L) is inducible, uninducible, or constitutive. 2 B 3 C 4 D inducible inducible constitutive uninducible constitutive inducible inducible E uninducible F G H > > >arrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning