Bio Final Lecture 37

The greatest expression of the lac operon occurs when lactose levels are _____. high and glucose levels are high high and glucose levels are low low and glucose levels are high low and glucose levels are low

What is the pattern of expression of β-galactosidase in lacI— cells and why? Constitutive expression, because there is no repressor No expression, because lactose is absent. Constitutive expression, because the galactoside permease gene is defective No expression, because the β-galactosidase gene is defective

If you wanted to prevent a regulatory protein from changing gene expression, you would have to prevent physical contact between the protein and _____. ribozymes ribosomes DNA mRNA

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the repressor gene (lacI), along with its promoter, to a position at some several thousand base pairs away from its normal position, we would expect the _____. repressor will no longer bind to the operator lac operon will be expressed continuously lac operon will function normally repressor will no longer bind to the inducer repressor will no longer be made

Which of the following characteristics, structures, or processes is common to bacteria and viruses? genetic material composed of nucleic acid ribosomes metabolism cell division independent existence

Viruses _____. use the host cell to copy themselves and then viruses synthesize their own proteins use the host cell to copy themselves and make viral proteins manufacture their own ATP, proteins, and nucleic acids metabolize food and produce their own ATP

There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant? It cannot bind to the inducer. It makes a repressor that binds CAP. It cannot bind to the operator. It cannot make a functional repressor. It makes molecules that bind to one another.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely? RNA polymerase will no longer transcribe permease. The cell will continue to metabolize but more slowly. The operon will still transcribe the lacZ and lacY genes, but the mRNA will not be translated. Beta galactosidase will not be produced. The three structural genes will be expressed normally.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the operator to the far end of the operon, past the transacetylase (lacA) gene, which of the following would likely occur when the cell is exposed to lactose? The repressor will no longer bind to the operator. The operon will never be transcribed. The inducer will no longer bind to the repressor. The structural genes will be transcribed continuously. The repressor protein will no longer be produced.

A compound known as X-gal is widely used in molecular genetic research. When wild-type (normal) E. coli is grown on medium containing X-gal, the bacterial colonies turn blue. In contrast, when lacZ mutants are grown on medium containing X-gal, the bacterial colonies remain their normal white color. X-gal is likely to be a compound _____. chemically similar to galactose that can be transported only into lacA mutants chemically similar to glucose chemically similar to lactose that cannot be transported into lacZ mutants

Colonies of what color are produced by cells with functioning copies of β-galactosidase? white blue

Colonies of what color are produced by cells with mutations in the lacZ or in the lacY genes? blue white

Suppose you analyze the protein-coding sequence of the lacZ and lacY genes of cells from the three mutant colonies and find that these sequences are wild type (normal). What other region of the lac operon might be altered to account for the mutant phenotype of these colonies? the inducer the lacI gene the repressor the lac promoter

Which of the following leads to the highest rate of lac operon transcription? low lactose levels and low glucose levels high lactose levels and high glucose levels high lactose levels and low glucose levels low lactose levels and high glucose levels intermediate levels of lactose and glucose

You are studying an operon that encodes a polycistronic mRNA for three structural genes of approximately equal size: gene A, gene B, and gene C. The mRNA is stable for about 2 minutes, and the genes are found in the order A, B, C from the 5' end to the 3' end. If you knew that the mRNA was degraded by a 3'→5' exonuclease, which of the following ratios of functional proteins (A:B:C) would you most likely observe? 3:5:8 5:7:10 10:7:5 1:1:1 5:10:10

Which of the following parts in the human body CANNOT be infected by a virus? brain skeletal muscle blood cells none of the above, as they can all be infected by viruses

Which of the following statements about viruses is incorrect? Since viruses can persist on their own, they can replicate independently outside of a host. Bacteriophage are viruses that infect bacteria. Influenza is an example of a virus that contains a segmented genome. Viruses contain nucleic acids. The most common type of genome found in a virus is a linear double stranded DNA.

Which of the following statements about phage is/are correct? Choose all that apply. They are obligate intracellular parasites that infect bacteria. They produce their own supply of ATP. They always contain circular RNA genomes. They are replicated only within bacterial cells. They encode most of the enzymes and proteins required for intracellular metabolism and survival. They enter the cells they infect through endocytosis.

virus

lateral gene transfer

epidemic

pandemic

virulent

AIDS

HIV

to fight viruses

virion

capsid

positive sense RNA virus

negative sense RNA virus

ambisense RNA virus

replicative growth

Which one of the following examples of regulation would save a cell the most energy? Preventing a transcription factor from binding a promoter Inhibiting a snRNP complex from recognizing an intron/exon junction Degrading an mRNA Stalling a ribosome through the use of a non-preferred codon Keeping a folded polypeptide from possessing biological activity until it has been phosphorylated