Biology Practice Test 4|50 Questions with Verified Answers
1) Which of the following is the best modern definition of evolution?
A) descent with
... [Show More] modification
B) change in the number of genes in a population over time
C) survival of the fittest
D) inheritance of acquired characters - CORRECT ANSWER A
2) 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 strong-beak alleles increased in each bird as the drought persisted. - CORRECT ANSWER B
3) 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 - CORRECT ANSWER C
4) Cystic fibrosis is a genetic disorder in homozygous recessives that causes death during the teenage years. If 9 in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant (A1) and recessive (A2) alleles according to the Hardy-Weinberg model?
A) f(A1) = 0.9997, f(A2) = 0.0003
B) f(A1) = 0.9800, f(A2) = 0.0200
C) f(A1) = 0.9700, f(A2) = 0.0300
D) f(A1) = 0.9604, f(A2) = 0.0392 - CORRECT ANSWER C
5) 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 - CORRECT ANSWER B
6) An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake?
A) directional selection
B) disruptive selection
C) a founder event
D) a genetic bottleneck - CORRECT ANSWER D
7) The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. 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 Hardy-Weinberg equilibrium
B) heterozygote advantage and stabilizing selection
C) mutation and natural selection
D) founder effect and genetic drift - CORRECT ANSWER D
8) Which of the following is the most predictable outcome of increased gene flow between two populations?
A) lower average fitness in both populations
B) higher average fitness in both populations
C) increased genetic difference between the two populations
D) decreased genetic difference between the two populations - CORRECT ANSWER D
9) Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing _____.
A) nonrandom mating
B) geographic isolation
C) genetic drift
D) gene flow - CORRECT ANSWER D
10) Currently the only predators of Galápagos marine iguanas are Galápagos hawks. Iguana body size is not correlated with risk of hawk predation, although small iguanas can sprint faster than large iguanas. If predators (for example, cats) that preferably catch and eat slower iguanas are introduced to the island, iguana body size is likely to _____ in the absence of other factors; the iguanas would then be under _____ selection.
A) increase; directional
B) increase; disruptive
C) decrease; directional
D) decrease; disruptive - CORRECT ANSWER C
11) In his transformation experiments, what did Griffith observe?
A) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
B) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.
C) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.
D) Mice infected with a pathogenic strain of bacteria can spread the infection to other mice. - CORRECT ANSWER A
12) How do we describe transformation in bacteria?
A) the creation of a strand of DNA from an RNA molecule
B) the creation of a strand of RNA from a DNA molecule
C) the infection of cells by a phage DNA molecule
D) assimilation of external DNA into a cell - CORRECT ANSWER D
13) After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait?
A) evidence that DNA was passed from the heat-killed strain to the living strain
B) evidence that protein passed from the heat-killed strain to the living strain
C) especially bright phosphorescence in the living strain
D) phosphorescence in descendants of the living cells - CORRECT ANSWER D
14) Which of the following investigators was (were) responsible for the following discovery?
In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.
A) Alfred Hershey and Martha Chase
B) Oswald Avery, Maclyn McCarty, and Colin MacLeod
C) Erwin Chargaff
D) Matthew Meselson and Franklin Stahl - CORRECT ANSWER C
15) Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
A) 8%
B) 16%
C) 42%
D) 58% - CORRECT ANSWER A
16) Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?
A) Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.
B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.
C) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes.
D) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not. - CORRECT ANSWER B
17) What is meant by the description "antiparallel" regarding the strands that make up DNA?
A) The twisting nature of DNA creates nonparallel strands.
B) The 5' to 3' direction of one strand runs counter to the to direction of the other strand.
C) Base pairings create unequal spacing between the two DNA strands.
D) One strand contains only purines and the other contains only pyrimidines. - CORRECT ANSWER B
18) In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?
A) Additional proofreading will occur.
B) No replication fork will be formed.
C) Replication will occur via RNA polymerase alone.
D) Replication will require a DNA template from another source - CORRECT ANSWER B
19) In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the → direction?
A) primase
B) DNA ligase
C) DNA polymerase III
D) helicase - CORRECT ANSWER C
20) A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is _____.
A) UCA
B) UGA
C) TCA
D) ACU - CORRECT ANSWER A
21) The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A) A gene from an organism can theoretically be expressed by any other organism.
B) DNA was the first genetic material.
C) The same codons in different organisms translate into different amino acids.
D) Different organisms have different types of amino acids. - CORRECT ANSWER A
22) In the process of transcription, _____.
A) DNA is replicated
B) RNA is synthesized
C) proteins are synthesized
D) mRNA attaches to ribosomes - CORRECT ANSWER B
23) Codons are part of the molecular structure of _____.
A) a protein
B) mRNA
C) tRNA
D) rRNA - CORRECT ANSWER B
24) Which of the following occurs in prokaryotes but not in eukaryotes?
A) post-transcriptional splicing
B) concurrent transcription and translation
C) translation in the absence of a ribosome
D) gene regulation - CORRECT ANSWER B
25) Which of the following statements best describes the termination of transcription in prokaryotes?
A) RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase.
B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
C) Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome.
D) RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. - CORRECT ANSWER B
26) Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
A) start and stop codons
B) ribosomes and tRNA
C) several transcription factors
D) aminoacyl-tRNA synthetase - CORRECT ANSWER C
27) A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is _____.
A) TTT
B) UUA
C) UUU
D) AAA - CORRECT ANSWER D
28) Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _____.
A) binding of ribosomes to mRNA
B) binding of the anticodon to small subunit of the ribosome
C) attachment of amino acids to rRNAs
D) binding of the anticodon to the codon and the attachment of amino acids to tRNAs - CORRECT ANSWER D
29) A mutant bacterial cell has a defective aminoacyl-tRNA 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 lysine-specifying anticodons
D) the ribosome will skip a codon every time a UUU is encountered - CORRECT ANSWER B
30) Which of the following is a protein produced by a regulatory gene?
A) operon
B) inducer
C) promoter
D) repressor - CORRECT ANSWER D
31) A lack of which molecule would result in a cell's inability to "turn off" genes?
A) operon
B) inducer
C) promoter
D) corepressor - CORRECT ANSWER D
32) 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 - CORRECT ANSWER A
33) 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 - CORRECT ANSWER A
34) 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 - CORRECT ANSWER C
35) 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 - CORRECT ANSWER C
36) In positive control of several sugar-metabolism-related 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 - CORRECT ANSWER B
37) 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 - CORRECT ANSWER D
38) CAP is said to be responsible for positive regulation of the lac operon because _____.
A) CAP binds cAMP
B) CAP binds to the CAP-binding site
C) CAP prevents binding of the repressor to the operator
D) CAP bound to the CAP-binding site increases the frequency of transcription initiation - CORRECT ANSWER D
39) Imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?
A) The mutant will grow rapidly.
B) The mutant will require galactose for growth.
C) The mutant will show low levels of gene expression.
D) The mutant will show high levels of gene expression - CORRECT ANSWER C
40) Which of the three types of viruses shown above would you expect to include glycoproteins?
A) I only
B) II only
C) III only
D) I and II only - CORRECT ANSWER D
41) Which of the three types of viruses shown above would you expect to include a capsid(s)?
A) I only
B) II only
C) III only
D) I, II, and III - CORRECT ANSWER D
42) 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. - CORRECT ANSWER A
43) 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 - CORRECT ANSWER B
44) 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. - CORRECT ANSWER C
45) 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 - CORRECT ANSWER D
46) 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 - CORRECT ANSWER C
47) 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 - CORRECT ANSWER A
48) 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 - CORRECT ANSWER B
49) 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. - CORRECT ANSWER B
50) 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
. - CORRECT ANSWER B [Show Less]