Given the following genotype I + P + O^c lacZ + lacY -/I + P + O + lacZ + lacY-w
ID: 94996 • Letter: G
Question
Given the following genotype I + P + O^c lacZ + lacY -/I + P + O + lacZ + lacY-which statement is true? A) E.coli will produce B-galactosidase but not permease, and will NOT grow on lactose medium B) E.coli will produce permease but not B-galactosidase, and will NOT grow on lactose medium C) E. coli will produce B-galactosidase and permease in presence of lac (inducible), and will grow on lac medium D) E. coli will produce neither B-galactosidase nor permease, and will NOT grow on lactose medium E) E. coli will produce B-galactosidase and permease regardless of lac presence (constitutive), and will grow on lac medium Given the following genotype: I^s P - O^c lacZ + lacY + which of the following mutations act in "trans"? A) Operator mutation B) Repressor mutation C) Promoter mutation D) Both promoter and operator mutations E) none of the above In prokaryotic gene expression, which is the best definition of an operon? A) A cluster of genes that are regulated by a single promoter B) A DNA-binding protein that regulates gene expression C) A non-coding, regulatory DNA sequence that is bound by RNA polymerase D) A non-coding, regulatory DNA sequence that is bound by a repressor protein The L-arabinose operon in E.coli encodes enzymes necessary for the breakdown of the sugar arabinose. If arabinose is absent, the protein AraC binds near the promoter preventing their transcription. If arabinose is present, it binds to AraC and prevents it from binding to the promoter. Which of the following best summarizes the AraC operon? a) ara is an inducible operon- - arabinose acts as the inducer b) ara is an induciblc operon- AraC acts as the inducer c) ara is a repressible operon- arabinose acts as the repressor d) ara is a repressible operon- arabinose acts as the repressor c) none of the above You are studying a population of Spartacus guppies, and determine that mean body length is 18cm. You want to try to increase the size of your school of fish, and select several parent fish with a mean body length of 24cm to contribute offspring to the next generation. The body length of their offspring is on average 20cm. What is the probable narrow-sense heritability for this trait? A) 20/24 B) 2/6 C) 24 - 4 D) 4/6 E) 18/20Explanation / Answer
14) The answer is A. lacY produces permease but in the given genotype it is absent. Hence the cell will not produce permease which restricts the entry of lactose. So the cell cannot utilize lactose that leads to its death.
15) The answer is B. Mutation in repressor gene causes repressor protein that cannot bind to the inducer but can bind to promoter and operator and permanently turns the operon off. This is an example of trans dominant effect.
16) The answer is A. An operon is a group of genes regulated by a common promoter and operator ultimately generating a polycistronic mRNA. Examples are ara operon, trp operon and lac operon.
17) The answer is A. AraC binds to the arabinose molecule present in the vicinity. This binding leads to the change in the confirmation of AraC which makes it misfit to bind to the promoter. Thus the ara operon is switched on.
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