BIO 4

A mutation that inactivates a regulatory gene of a repressible operon in an E. coli cell would result in _____. A) continuous transcription of the structural gene controlled by that regulator B) complete inhibition of transcription of the structural gene controlled by that regulator C) irreversible binding of the repressor to the operator D) continuous translation of the mRNA because of alteration of its structure

A

Which of the following human diseases is caused by a virus that requires reverse transcriptase to transcribe its genome inside the host cell? A) herpes B) HIV C) smallpox D) influenza

B

Why do RNA viruses appear to have higher rates of mutation? A) RNA nucleotides are more unstable than DNA nucleotides. B) Replication of their genomes does not involve proofreading. C) RNA viruses can incorporate a variety of nonstandard bases. D) RNA viruses are more sensitive to mutagens.

B

A lack of which molecule would result in a cell's inability to "turn off" genes? A) operon B) inducer C) promoter D) corepressor

D

Extracellular glucose inhibits transcription of the lac operon by _____. A) strengthening the binding of the repressor to the operator B) weakening the binding of the repressor to the operator C) inhibiting RNA polymerase from opening the strands of DNA to initiate transcription D) reducing the levels of intracellular cAMP

D

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population? A) population bottleneck and HardyWeinberg equilibrium B) heterozygote advantage and stabilizing selection C) mutation and natural selection D) founder effect and genetic drift

D

Which of the following supports the argument that viruses are nonliving? A) They are not cellular. B) Their DNA does not encode proteins. C) They have RNA rather than DNA. D) They do not evolve.

A

Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by _____. A) organizing gene expression, so that genes are expressed in a given order B) allowing each gene to be expressed an equal number of times C) allowing an organism to adjust to changes in environmental conditions D) allowing environmental changes to alter a prokaryote's genome

C

What is the main structural difference between enveloped and nonenveloped viruses? A) Enveloped viruses have their genetic material enclosed by a layer made only of protein. B) Nonenveloped viruses have only a phospholipid membrane, while enveloped viruses have two membranes, the other one being a protein capsid. C) Enveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane. D) Both types of viruses have a capsid and phospholipid membrane; but in the nonenveloped virus the genetic material is between these two membranes, while in the enveloped virus the genetic material is inside both membranes.

C

Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation? A) inducer B) promoter C) transcription factor D) cAMP

A

What is the function of reverse transcriptase in retroviruses? A) It uses viral RNA as a template for DNA synthesis. B) It converts host cell RNA into viral DNA. C) It translates viral RNA into proteins. D) It uses viral RNA as a template for making complementary RNA strands.

A

Which of the following is the best modern definition of evolution? A) descent with modification B) change in the number of genes in a population over time C) survival of the fittest D) inheritance of acquired characters

A

A mutant bacterial cell has a defective aminoacyltRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that _____. A) none of the proteins in the cell will contain phenylalanine B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU C) the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysinespecifying anticodons D) the ribosome will skip a codon every time a UUU is encountered

B

HIV is inactivated in the laboratory after a few minutes of sitting at room temperature, but the flu virus is still active after sitting for several hours. What are the practical consequences of these findings? A) HIV can be transmitted more easily from person to person than the flu virus B) The flu virus can be transmitted more easily from person to person than HIV C) This property of HIV makes it more likely to be a pandemic than the flu virus D) Disinfecting surfaces is more important to reduce the spread of HIV than the flu

B

In positive control of several sugarmetabolismrelated operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP activity in stimulating transcription? A) an increase in glucose and an increase in cAMP B) a decrease in glucose and an increase in cAMP C) an increase in glucose and a decrease in cAMP D) a decrease in glucose and a decrease in the repressor

B

In the formula for determining a population's genotype frequencies, the "2" in the term 2pq is necessary because _____. A) the population is diploid B) heterozygotes can come about in two ways C) the population is doubling in number D) heterozygotes have two alleles

B

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

B

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true? A) Each bird evolved a deeper, stronger beak as the drought persisted. B) Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted. C) Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation. D) The frequency of the strongbeak alleles increased in each bird as the drought persisted.

B

Genetic variation _____. A) is created by the direct action of natural selection B) arises in response to changes in the environment C) must be present in a population before natural selection can act upon the population D) tends to be reduced by when diploid organisms produce gametes

C

In many ways, the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes. Therefore, which of the following would you expect of the genes of a bacteriophage? A) regulation via acetylation of histones B) positive control mechanisms rather than negative C) control of more than one gene in an operon D) reliance on transcription activators

C

The lactose operon is likely to be transcribed when _____. A) there is more glucose in the cell than lactose B) there is glucose but no lactose in the cell C) the cyclic AMP and lactose levels are both high within the cell D) the cAMP level is high and the lactose level is low

C

Which of the following accounts for someone who has had regular herpes virus mediated cold sore or genital sore flareups? A) reinfection by a closely related herpesvirus of a different strain B) reinfection by the same herpesvirus strain C) copies of the herpesvirus genome permanently maintained in host nuclei D) copies of the herpesvirus genome permanently maintained in host cell cytoplasm

C

Which of the following is characteristic of the lytic cycle? A) Viral DNA is incorporated into the host genome. B) The viral genome replicates without destroying the host. C) A large number of phages are released at a time. D) The virus—host relationship usually lasts for generations.

C

The host range of a virus is determined by _____. A) the enzymes carried by the virus B) whether its nucleic acid is DNA or RNA C) the proteins in the host's cytoplasm D) the proteins on its surface and that of the host

D

Which of the following is a protein produced by a regulatory gene? A) operon B) inducer C) promoter D) repressor

D