1) If a mutation deactivated a regulatory gene of a repressible operon in an E. coli cell which of the following describes the most likely outcome?
A. continuous transcription of the structural gene controlled by that regulator
B. continuous translation of the mRNA because of alteration of its structure
C. irreversible binding of the repressor to the operator
D. complete inhibition of transcription of the structural gene controlled by that regulator
A
2) A mutation in E. coli results in a molecule known as a "super-repressor" because the operon is permanently repressed. Which of the following describes the most likely effect of the mutation on the repressor protein?
A. It cannot bind to the inducer.
B. It cannot bind to the operator.
C. It makes a repressor that binds CAP.
D. It cannot make a functional repressor.
A
3) If a researcher 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 results would be most likely?
A. RNA polymerase will no longer transcribe permease.
B. Beta galactosidase will not be produced.
C. The operon will still transcribe the lacZ and lacY genes, but the mRNA will not be translated.
D. The three genes of the lac operon will be expressed normally.
B
4) If a researcher moves the operator to the far end of the operon, which of the following processes would likely occur when the cell is exposed to lactose?
A. The operon will never be transcribed.
B. The inducer will no longer bind to the repressor.
C. The genes of the lac operon will be transcribed continuously.
D. The repressor will no longer bind to the operator.
C
5) If a researcher moves the repressor gene (lacI) and its promoter, to a position at some several thousand base pairs away from its normal position, which of the following describes the most likely effect on the lac operon?
A. The lac operon will function normally.
B. The repressor will no longer bind to the inducer.
C. The lac operon will be expressed continuously.
D. The repressor will no longer bind to the operator.
A
6) According to the lac operon model proposed by Jacob and Monod, what is predicted to occur if the operator is removed from the operon?
A. The lac operon would be transcribed continuously.
B. Only lacY would be transcribed.
C. Only lacZ would be transcribed.
D. Genes involved in glucose metabolism would not be transcribed.
A
7) Which of the following is the most likely phenotypes of a yeast mutant that contains histones that are resistant to acetylation?
A. The mutant will show increased levels of gene expression.
B. The mutant will show decreased levels of gene expression.
C. The mutant will grow rapidly.
D. The mutant will require galactose for growth.
B
8) Which of the following statements correctly describes the primary difference between enhancers and proximal control elements?
A. Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter.
B. Enhancers are transcription factors; proximal control elements are DNA sequences.
C. Enhancers improve transcription; proximal control elements inhibit transcription.
D. Enhancers are long regions of DNA; proximal control elements are shorter RNA molecules that stand in for DNA.
A
9) Which of the following best explains why a neuron and a pancreatic cell isolated from the same individual contain different sets of proteins?
A. Each cell type needs different proteins and, therefore, they break down proteins they don't need.
B. The set of genes in each cell type are different, therefore, they express different proteins.
C. Each cell type contains different regulatory proteins and, therefore, they express different proteins.
D. The genes in each cell type have different promoters and, therefore, they respond to different regulatory proteins.
C
10) Gene expression is often assayed by measuring the level of mRNA produced from a gene. Which of the following levels of the control of gene expression can by analyzed by this type of assay?
A. alternative splicing
B. translational control
C. replication control
D. transcriptional control
D
11) Which of the following results is most likely to occur if acetylation of histone tails in the chromatin of embryonic cells is increased?
A. inactivation of the selected genes
B. increased chromatin condensation
C. decreased binding of transcription factors
D. decreased chromatin condensation
D
12) If the DNA of a mammalian promoter region experiences increased methylation on cytosine (C) which of the following results is most likely to occur?
A. decreased chromatin condensation
B. inactivation of the gene
C. higher levels of transcription of certain genes
D. activation of histone tails for enzymatic function
B
13) Which of the following statements best describes the characteristics of siRNA?
A. a single-stranded RNA that can fold into cloverleaf patterns due to regions of internal complementary base pairs
B. a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor
C. a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits
D. a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
D
14) A researcher introduced many copies of a double-stranded RNA into a culture of mammalian cells and used a fluorescent probe to follow it. She found that the introduced strands separated; one strand degraded and the other single-stranded RNA remained. The remaining strand is able to do which of the following?
A. bind to complementary regions of target mRNAs
B. attach to histones in the chromatin
C. activate other siRNAs in the cell
D. act as a template for transcription
A
15) A researcher introduced many copies of a double-stranded RNA into a culture of mammalian cells and used a fluorescent probe to follow it. Later she finds that the introduced strands separate into single-stranded RNAs and she hypothesizes that the molecules is acting as an miRNA. Which of the following pieces of evidence would support her claim?
A. After separating the strands she introduced shut down all translation.
B. The rate of accumulation of the polypeptide encoded by the target mRNA is reduced.
C. The degradation rate of the single strand is slower than that of other cellular mRNA's.
D. The amount of the RNA she introduced increases due to transcription
B
16) Which of the following conclusions is consistent with the fact that plants can be cloned from somatic cells?
A. Differentiation results in the loss of non-expressed genes.
B. Differentiation does not occur in plants.
C. Differentiated cells retain all the genes of the zygote.
D. The differentiated state is normally very unstable.
C
17) Which of the following explains why introducing the MyoD protein into a fat cell causes that cell to become a muscle cell but adding it to a neuron will have no effect?
A. Neurons are a differentiation step after muscle cells, they cannot go "backwards."
B. Fat cells are undifferentiated, the MyoD protein causes them to differentiate.
C. MyoD is causes positive feedback of MyoD expression in fats cells but not neurons.
D. Muscle-specific gene expression requires a protein that neurons do not make.
D
18) In wildtype Drosophila embryos, the bicoid mRNA is localized to the anterior end of the embryo. If bicoid mRNA was injected into the embryo's posterior end as well, which of the following developmental events would occur?
A. The embryo would show anterior structures at both ends of the embryo.
B. The embryo would develop normally.
C. The embryo would have altered segmentation.
D. The embryo would grow extra wings and legs.
A
19) A cell is considered to be differentiated if it has which of the following characteristics?
A. The cell loses connections to the surrounding cells.
B. The cell appears to be different from the surrounding cells.
C. The cell replicates by the process of mitosis.
D. The cell produces proteins specific to a particular cell type.
D
20) In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated?
A. genes involved in control of the cell cycle
B. genes coding enzymes that act in the colon
C. genes that are especially susceptible to mutation
D. genes regulating cell division in colon bacteria
A
21) Which of the following events or characteristics is the most likely explanation for why an individual experiences regular herpesvirus-mediated cold sore or genital sore flare-ups?
A. They have been reinfection by exposure to a different, but closely related herpesvirus strain.
B. Copies of the herpesvirus genome permanently maintained in host nuclei are periodically "activated."
C. Copies of herpesvirus particles that have escaped the immune system periodically experience conditions that allow them to replicate and infect cells.
D. They have been reinfection by exposure to the same herpesvirus strain.
B
22) Since viral gene expression is regulated by the same machinery as host cell gene expression, which of the following is most likely involved in regulating expression of bacteriophage genes?
A. reliance on transcription activators
B. regulation via acetylation of histones
C. positive control mechanisms rather than negative
D. coordinate control of more than one gene in an operon
D
23) A newly identified virus has a single-stranded RNA genome that is used as mRNA after infection. Its capsid is 25-30 nm in diameter and contains 180 identical capsomeres. Which of the following processes would be the best to follow to analyze the reproduction of this virus in a host cell?
A. formation of new transcription factors
B. mRNA splicing
C. DNA replication rate
D. translation rate
D
24) Use the following information to answer the question. Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. The RNA genome has a 5′ RNA cap instead of a 5′ methyl-G cap. This is followed by a non-translated leader sequence and then a single long protein-coding region (~7,000 nucleotides) followed by a poly-A tail. Infected cells were incubated with radioactive amino acids and viral proteins were isolated. After a short incubation with radioactive amino acids only very long viral proteins were seen, while longer periods of labeling result in several short polypeptides of different lengths. Which of the following conclusions is most consistent with the results described?
A. Host cell ribosomes translate the viral coding region and poly-A tail at different times resulting in the different populations of proteins.
B. The RNA is translated into short polypeptides, which are then assembled into large complexes.
C. The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.
D. The RNA is first translated into a single long protein, which is then cleaved into shorter ones.
D
25) Cells were infected with approximately 1,000 copies of either virus A or virus B at the 0 time point. At five-minute intervals, a sample of the virus and cell mixture was removed. All intact cells were removed from the sample, and the number of viruses per milliliter of culture was determined and plotted in the graph above. In a second experiment, 1 mL of each viral sample collected at 90 minutes post infection was mixed with new, uninfected cell cultures. Which of the following best describes these new cultures?
A. The new culture infected with virus A will result in more infected cells than the new culture infected with virus B.
B. The new culture infected with virus A will require 60 minutes before new viral particles will be released into the culture.
C. The new culture infected with virus B will have a shorter lytic cycle than seen in the original virus B culture.
D. The new culture infected with virus B will plateau with approximately 50,000 viral particles per milliliter of culture.
A
26) Which of the following best explains the results?
A. Virus P is capable of both lysogenic and lytic cycles.
B. The chemical added to culture B1 caused the cells to lyse.
C. The cells in culture B2 were resistant to infection while the cells in B1 were not.
D. Culture B1 was contaminated and infected with virus when the chemical was added.
A
27) Which of the following viruses would most likely contain reverse transcriptase?
A. an RNA-based lysogenic virus
B. an RNA-based lytic virus
C. a DNA-based lytic virus
D. a DNA-based lysogenic virus
A
28) If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins during processing in the Golgi apparatus, which of the following processes is most likely to occur?
A. The virus would be unable to reproduce within the host cell.
B. The viral envelope proteins would not have glycoproteins added to them and might not arrive at the host plasma membrane.
C. The viral capsid proteins would not have glycoproteins added to them and might not arrive at the host plasma membrane.
D. The viral core proteins would not have glycoproteins added to them and might not arrive at the host plasma membrane.
B
29) Viruses require host cell's machinery to make copies of themselves. However, some viruses that infect humans require mechanisms that do not normally occur in human cells. Which of the following describes how the viruses can replicate in human cells?
A. The viral genome codes for specialized enzymes not found in the host cells.
B. The virus can enter these cells but new viruses will not be made until an environmental change triggers a switchover.
C. Viruses can stay in a quiescent state until the host cell evolves this ability.
D. The virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles.
A
30) Azidothymidine (AZT) is a reverse transcriptase inhibitor that was part of the first class of antiviral drugs developed to treat HIV infection. Which of the following correctly describes how these drugs inhibited HIV infection?
A. The drugs prevented host cells from producing the enzymes used by the virus to replicate its genome.
B. The drugs targeted and destroyed the viral genome before it could be reverse transcribed into DNA.
C. The drug bonded to the viral reverse transcriptase enzyme and prevented it from making a DNA copy of viral RNA.
D. The drugs bonded to the viral dsDNA and prevented it from being able to be used as a template for replication.
C
31) Humans have harmless E. coli strains that reside in the intestines. O157:H7 is an E. coli strain reported to cause several food poisoning deaths. Evidence suggests that the virulence of O157:H7 is caused by genes from a virus that infects bacteria. Considering this evidence, which of the following statements most likely explains how the O157:H7 population acquired the genetic variation that distinguishes it from the harmless E. coli strains?
A. Viral envelope proteins bound receptors on the bacteria, allowing the viral genetic material to enter the cytoplasm and be translated into proteins that increased that bacterium's virulence.
B. The virus infected the bacterium, and the bacterial population replicated with a copy of the phage genome in each new bacterium.
C. The virus entered the bacterial cell, allowing the bacteria's cellular machinery to create new viruses.
D. The virus entered the cell and reassorted to acquire specific genes from the bacteria to increase the virulence of the virus.
B
32) A researcher is studying a single plant infected with tobacco mosaic virus (TMV). She crushes three of the plant's leaves in a small amount of water and stores the sample in the refrigerator overnight. The next day she sprays the mixture onto a new set of tobacco plants she had recently trimmed and repotted. Which of the following results will most likely occur?
A. These plants would not show any disease symptoms but vertical transmission would cause their offspring to be diseased.
B. The plant cuticle would protect them from infection and they would continue growing as before.
C. The plants would develop the typical symptoms of TMV infection and would be able to transmit the disease.
D. The plants would become infected with TMV, but extracts from these plants would be unable to infect other plants.
C
33) Which of the following statements best reflects what we know about how influenza virus moves between species?
A. In an animal, such as a pig, the influenza virus is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected.
B. An influenza virus from a human epidemic or pandemic infects birds; the birds replicate mutant versions of that virus and then pass the new forms back to humans.
C. An animal, such as a pig, is infected with more than one strain of the influenza virus and the genomes reassort into new combinations that can facilitate spread to other species.
D. An influenza virus fuses with a different type of virus (like HSV) and gains new DNA which enable the new virus to be transmitted to a wider variety of host species.
C
34) An infectious substance capable of causing disease in plants is isolated and researchers want to determine whether the substance is a bacterium or a virus. Which of the following methods will best allow them to determine the type of infectious agent they have isolated?
A. Culture the substance with plant cells, and then determine whether the cells lyse.
B. Culture the substance on nutritive medium, away from any plant cells.
C. Treat the sample with proteases that digest all proteins, and then determine whether the substance is still infectious.
D. Treat the substance with enzymes that destroy all nucleic acids, and then determine whether the substance is still infectious.
B
35) Which of the following methods would be best to use for distinguishing between an infectious agent that is a virus and one that is a prion?
A. Filter the substance to remove all elements smaller than what can be easily seen under a light microscope.
B. Treat the sample with proteases that digest all proteins, and then determine whether the substance is still infectious.
C. Treat the substance with enzymes that destroy all nucleic acids, and then determine whether the substance is still infectious.
D. Culture the substance on nutritive medium, away from any cells.
C
36) Use the following information to answer the question. The herpes viruses are enveloped DNA viruses that cause disease in vertebrates and in some invertebrates such as oysters. Some of the human forms are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can later reactivate, replicate, and infect others. Which of the following treatments would have the best chance of lowering the number of new cases of infection?
A. Interfere with new viral replication in preexisting cases of herpes simplex virus.
B. Vaccinate of all persons with preexisting cases of herpes simplex virus.
C. Educate people about ways to disinfect surfaces that came in contact with herpes simplex virus.
D. Treat herpes simplex virus lesions to shorten the breakout.
A
37) Which of the following best explains the inability of bacteria to correctly express the protein products of plasmid containing an unmodified mammalian gene?
A. prokaryotes use a different genetic code from that of eukaryotes
B. bacteria cannot remove eukaryotic introns
C. bacterial RNA polymerase cannot make RNA complementary to mammalian DNA
D. bacteria translate only mRNAs that have multiple messages
B
38) Which of the following reasons best explains why sequencing an entire genome, such as that of C. elegans, a nematode, is important for genetic research?
A. It allows researchers to use the sequence to build a "better" nematode, which is resistant to disease.
B. A sequence that is found to have a particular function in the nematode is likely to have a closely related function in vertebrates.
C. It allows research on a group of organisms we do not usually care much about.
D. A sequence that is found to have no introns in the nematode genome is likely to have acquired the introns from vertebrates.
B
39) When attempting to introduce a particular fragment of DNA into the genome of an animal cell which of the following methods would be most successful?
A. infecting the mouse cell with a Ti plasmid
B. CRISPR/Cas9 recombination
C. RNA-seq followed by genetic profiling
D. in vitro hybridization of the DNA with the cell's genome
B
40) The activity of which of the following enzymes would produce a molecule of DNA as represented in the figure?
A. DNA polymerase
B. a restriction enzyme (endonuclease)
C. ligase
D. RNA polymerase
B
41) The segment of DNA shown in the figure has restriction sites I and II, which create restriction fragments A, B, and C. Which of the gels produced by electrophoresis best represents the separation and identity of these fragments?d
CAB spaced out
42) In large-scale, genome-wide association studies in humans, which of the following types of genetic markers are typically sought by researchers?
A. specific SNPs inherited more frequently by members within a family than by unrelated individuals
B. SNPs found approximately 100-300 bases apart within the genome
C. specific SNPs found more often in persons with a particular disorder than in healthy controls
D. SNPs where one allele is found in two or more adjacent genes
C
43) A person is heterozygous for a locus on Chromosome 1. The first copy of Chromosome 1 has the sequence 5′-AACTACGA-3′; the second copy has the sequence 5′-AACTTCGA-3′. Which of the following statements correctly describes theses sequences?
A. They contain a SNP that may be useful for genetic mapping.
B. They identify a location where only one copy could be cut by a restriction enzyme.
C. They may carry out RNA interference.
D. They contain an STR that may be useful for forensic analysis
A
44) Reproductive cloning of human embryos is generally considered unethical. However, on the subject of therapeutic cloning, there is a wider divergence of opinion. Which of the following statements provides the best argument in support of therapeutic cloning?
A. A clone that lives until the blastocyst stage does not yet have human DNA.
B. The use of adult stem cells is likely to produce more cell types than the use of embryonic stem cells.
C. Cloning to produce stem cells relies on a different initial procedure than reproductive cloning.
D. Cloning to produce embryonic stem cells may lead to great medical benefits for many.
D
45) Which of the following statements correctly describes one of the main differences between embryonic stem cells and adult stem cells?
A. Embryonic stem cells can continue to reproduce for an indefinite period, and adult stem cells cannot.
B. Embryonic stem cells are used to provide cells for repair of diseased tissue, and adult stem cells are not.
C. Embryonic stem cells only differentiate into only eggs and sperm, and adult stem cells differentiate into any type of cell.
D. Embryonic stem cells can give rise to all cell types in the organism, and adult stem cells cannot.
D
46) Which of the following is an ethical question regarding the use of CRISPR-Cas9 gene editing in humans?
A. Should we be able to determine information about individuals' genomes?
B. Should we be able to reduce the prevalence of human disease?
C. Should we be able to use try to use approaches developed in other model systems (for example, fruit flies, mice) in humans?
D. Should we be able to select and control the genetic makeup of the human population?
D
47) Which of the following describes an advantage of establishing and using a human reference genome in a bioinformatics investigation?
A. It represents the entire genome of one individual who acts as a standard for comparison.
B. Filling in remaining gaps would be more work than it is worth, so the reference has been set.
C. It is continuously revised as new data are collected and represents current consensus.
D. "Next generation" sequencing efforts can use it to see if their output is correct.
C
48) An indigenous group uses a certain plant for medicinal purposes. Their scientists are most likely to find which of the following in the genome annotation for the medicinal plant?
A. the cellular location of mRNAs expressed within different plant tissues
B. the plant's proteins that are medically important
C. the sequences show similarities with known functional domains
D. the relative levels of mRNA transcripts produced by the plant
C
49) What can proteomics reveal that genomics cannot?
A. the movement of transposable elements within the genome
B. the set of proteins present within a cell or tissue type
C. the number of genes characteristic of a species
D. the patterns of alternative splicing
B
50) Crickets and fruit flies are both insects. Which of the following statements could explain why a certain cricket genome has eleven times as many base pairs as that of the fruit fly, Drosophila melanogaster?
A. Crickets have higher gene density.
B. Crickets must make many more proteins.
C. Drosophila are more complex organisms.
D. Crickets must have more noncoding DNA.
D
51) Which of the following statements best explains why it is more difficult to determine a complete eukaryotic genome sequence than it is to determine the complete genomes of bacteria or archaea?
A. Eukaryotic DNA has a high proportion of G-C base pairs which makes sequencing difficult to complete.
B. Eukaryotic genomes contain sequences for hard-to-find proteins.
C. Eukaryotic proteins are larger in size are encoded by longer genes.
D. Eukaryotes have a large amount of repetitive DNA making sequence alignment difficult.
D
52) Which of the following describes a difference between transposable elements and short tandem repeats (STRs)?
A. STRs occur within introns; transposable elements occur within exons
B. STRs contain much larger repeated units those found in transposable elements
C. STRs make up only a small percentage of a given genome while transposable elements often make up larger parts of a given genome
D. STRs may result in phenotypic differences between individuals; transposable elements are non-coding regions.
C
53) Unequal crossing over during prophase I can result in one sister chromosome with a deletion and another with a duplication. Hemoglobin Lepore is a form of hemoglobin that is missing a series of amino acids. If this form was caused by unequal crossing over, which of the following is the most likely consequence?
A. Each of the genes in the hemoglobin gene family must show the same deletion.
B. The deleted region must be located in a different area of the individual's genome.
C. There should also be individuals whose hemoglobin contains a tandem repeat of the amino acid sequence that was deleted in hemoglobin Lepore.
D. The gene with the deletion must have undergone exon shuffling.
C
54) Which of the following statements best explains the different arrangements of these blocks in the genomes of these two species?
A. During evolutionary time, these sequences separated and have returned to their original positions in the mouse.
B. Chromosomal translocations have moved blocks of sequences to other chromosomes.
C. DNA sequences within these blocks have become increasingly divergent.
D. dSequences represented have duplicated at least three times resulting in this arrangement.
B
55) If gene duplication occurs to its ultimate extent and doubles all genes in a genome, which of the following outcomes is most likely to occur?
A. creation of a diploid
B. creation of a polyploid
C. creation of a pseudogene
D. creation of a gene cluster
B
56) Which of the following statements explains how errors during meiosis that result in an extra copy of a chromosome can facilitate evolution?
A. The genome is redundant and adding additional copies reinforces the redundancy.
B. Evolution requires fit individuals and an increase in the number of genes in a genome correlates with increased fitness.
C. Over time, mutations can accumulate in the extra sets of genes and allow evolution of novel functions.
D. A polyploid individual that results could mate with an individual that is deficient for other chromosomes.
C