AP Bio 14-18
A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer? a. colorectal only b. lung and breast c. small intestinal and esophageal d. lung only e. lung and prostate
A
A researcher is using adult stem cells and comparing them to other adult cells from the same tissue. Which of the following is a likely finding? a. The cells from the two sources exhibit different patterns of DNA methylation. b. Adult stem cells have more DNA nucleotides than their counterparts. c. The two kinds of cells have virtually identical gene expression patterns in microarrays. d. The nonstem cells have fewer repressed genes. e. The nonstem cells have lost the promoters for more genes.
A
Cell differentiation always involves a. the production of tissue-specific proteins, such as muscle actin. b. the movement of cells. c. the transcription of the myoD gene. d. the selective loss of certain genes from the genome. e. the cell's sensitivity to environmental cues, such as light or heat.
A
Figure 18.1 Types of DNA sequences in the human genome. The pie chart in Figure 18.1 represents the relative frequencies of the following in the human genome: I. repetitive DNA unrelated to transposons II. repetitive DNA that includes transposons III. unique noncoding DNA IV. introns and regulatory sequences V. exons Which region is occupied by exons only (V)? a. A b. B c. C d. D e. E
A
Homeotic genes a. encode transcription factors that control the expression of genes responsible for specific anatomical structures. b. are found only in Drosophila and other arthropods. c. are the only genes that contain the homeobox domain. d. encode proteins that form anatomical structures in the fly. e. are responsible for differentiation in muscle cells.
A
Homeotic genes contain a homeobox sequence that is highly conserved among very diverse species. The homeobox is the code for that domain of a protein that binds to DNA in a regulatory developmental process. Which of the following would you then expect? a. that homeotic genes are selectively expressed over developmental time b. that a homeobox-containing gene has to be a developmental regulator c. that homeoboxes cannot be expressed in nonhomeotic genes d. that all organisms must have homeotic genes e. that all organisms must have homeobox-containing genes
A
Humans have 23 pairs of chromosomes. In contrast, chimpanzees have 24 pairs of chromosomes and lack any pair resembling the long human chromosome 2 pair; instead, chimpanzees have two pairs of medium-sized chromosomes. What is the most likely explanation for these differences in the human and chimpanzee genomes? a. The common ancestor of humans and chimpanzees had 24 pairs of chromosomes, and at some point in the human lineage, two chromosomes fused end to end, providing some selective advantage. b. The common ancestor of humans and chimpanzees had 23 pairs of chromosomes, but when chimpanzees evolved, one of the chromosomes broke in half. c. At some point in evolution, human ancestors and chimpanzee ancestors were able to mate and produce fertile offspring, making a new species. d. Chromosome breakage resulted in additional centromeres being made, allowing meiosis to proceed successfully. e. Transposable elements transferred significantly large segments of the chromosomes to new locations.
A
In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA. Table 17.1 shows the results of testing five viruses (A—E) for nuclease specificity, the ability of the viral genome to act as an mRNA, and the presence (+) or absence (—) of each virus's own polymerase. Based on Table 17.1, which virus meets the requirements for a bacteriophage? a. A b. B c. C d. D e. E
A
In animals, embryonic stem cells differ from adult stem cells in that a. embryonic stem cells can differentiate into more cell types than adult stem cells. b. adult stem cells can differentiate into more cell types than embryonic stem cells. c. embryonic stem cells have more genes than adult stem cells. d. embryonic stem cells have fewer genes than adult stem cells. e. embryonic stem cells are localized to specific sites within the embryo, whereas adult stem cells are spread throughout the body.
A
In humans, the embryonic and fetal forms of hemoglobin have a higher affinity for oxygen than that of adults. This is due to a. nonidentical genes that produce different versions of globins during development. b. identical genes that generate many copies of the ribosomes needed for fetal globin production. c. pseudogenes, which interfere with gene expression in adults. d. the attachment of methyl groups to cytosine following birth, which changes the type of hemoglobin produced. e. histone proteins changing shape during embryonic development.
A
In recent times, it has been shown that adult cells can be induced to become pluripotent stem cells (iPS). In order to make this conversion, what has been done to the adult cells? a. A retrovirus is used to introduce four specific regulatory genes. b. The adult stem cells must be fused with embryonic cells. c. Cytoplasm from embryonic cells is injected into the adult cells. d. An adenovirus vector is used to transfer embryonic gene products into adult cells. e. The nucleus of an embryonic cell is used to replace the nucleus of an adult cell.
A
Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation? a. inducer b. promoter c. RNA polymerase d. transcription factor e. cAMP
A
Muscle cells differ from nerve cells mainly because they a. express different genes. b. contain different genes. c. use different genetic codes. d. have unique ribosomes. e. have different chromosomes.
A
One of the characteristics of retrotransposons is that a. they code for an enzyme that synthesizes DNA using an RNA template. b. they are found only in animal cells. c. they generally move by a cut-and-paste mechanism. d. they contribute a significant portion of the genetic variability seen within a population of gametes. e. their amplification is dependent on a retrovirus.
A
The anticodon of a particular tRNA molecule is a. complementary to the corresponding mRNA codon. b. complementary to the corresponding triplet in rRNA. c. the part of tRNA that bonds to a specific amino acid. d. changeable, depending on the amino acid that attaches to the tRNA. e. catalytic, making the tRNA a ribozyme.
A
The cancer-causing forms of the Ras protein are involved in which of the following processes? a. relaying a signal from a growth factor receptor b. DNA replication c. DNA repair d. cell-cell adhesion e. cell division
A
The difference between vertical and horizontal transmission of plant viruses is that a. vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant. b. vertical transmission is the spread of viruses from the upper leaves to the lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level. c. vertical transmission is the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size. d. vertical transmission is the transfer of DNA from one type of plant virus to another, and horizontal transmission is the exchange of DNA between two plant viruses of the same type. e. vertical transmission is the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species.
A
The following questions refer to the simple metabolic pathway in Figure 14.1. A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation? a. an accumulation of A and no production of B and C b. an accumulation of A and B and no production of C c. an accumulation of B and no production of A and C d. an accumulation of B and C and no production of A e. an accumulation of C and no production of A and B
A
The functioning of enhancers is an example of a. transcriptional control of gene expression. b. a post-transcriptional mechanism to regulate mRNA. c. the stimulation of translation by initiation factors. d. post-translational control that activates certain proteins. e. a eukaryotic equivalent of prokaryotic promoter functioning.
A
The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called a. RNA interference. b. RNA obstruction. c. RNA blocking. d. RNA targeting. e. RNA disposal.
A
Which of the following is characteristic of the product of the p53 gene? a. It is an activator for other genes. b. It speeds up the cell cycle. c. It causes cell death via apoptosis. d. It allows cells to pass on mutations due to DNA damage. e. It slows down the rate of DNA replication by interfering with the binding of DNA polymerase.
A
Which of the following is the best predictor of how much damage a virus causes? a. ability of the infected cell to undergo normal cell division b. ability of the infected cell to carry on translation c. whether the infected cell produces viral protein d. whether the viral mRNA can be transcribed e. how much toxin the virus produces
A
Which of the following represents another example of the same phenomenon as that shown in Figure 18.2? a. the apparent centric fusion between two chromosome pairs of primates such as chimps to form the ancestor of human chromosome 2 b. the difference in the numbers of chromosomes in five species of one genus of birds c. the formation of several pseudogenes in the globin gene family subsequent to human divergence from other primates d. the high frequency of polyploidy in many species of angiosperms
A
A multigene family is composed of a. multiple genes whose products must be coordinately expressed. b. genes whose sequences are very similar and that probably arose by duplication. c. the many tandem repeats such as those found in centromeres and telomeres. d. a gene whose exons can be spliced in a number of different ways. e. a highly conserved gene found in a number of different species.
B
A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The charged transfer RNA molecules shown in Figure 14.4 (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. Figure 14.4 The dipeptide that will form will be a. cysteine-alanine. b. proline-threonine. c. glycine-cysteine. d. alanine-alanine. e. threonine-glycine.
B
A recent study compared the H. sapiens genome with that of Neanderthals. The results of the study indicated that there was a mixing of the two genomes at some period in evolutionary history. The data that suggested this were a. some Neanderthal sequences not found in humans. b. a number of modern H. sapiens with Neanderthal sequences. c. Neanderthal Y chromosomes preserved in the modern population of males. d. mitochondrial sequences common to both groups.
B
Antiviral drugs that have become useful are usually associated with which of the following properties? a. ability to remove all viruses from the infected host b. interference with viral replication c. prevention of the host from becoming infected d. removal of viral proteins e. removal of viral mRNAs
B
BRCA1 and BRCA2 are considered to be tumor-suppressor genes because a. they prevent infection by tumor viruses that cause cancer. b. their normal products participate in repair of DNA damage. c. the mutant forms of either one of these prevent breast cancer. d. the normal genes make estrogen receptors. e. they block penetration of breast cells by chemical carcinogens.
B
If a Drosophila female has a homozygous mutation for a maternal effect gene, a. she will not develop past the early embryonic stage. b. all of her offspring will show the mutant phenotype, regardless of their genotype. c. only her male offspring will show the mutant phenotype. d. her offspring will show the mutant phenotype only if they are also homozygous for the mutation. e. only her female offspring will show the mutant phenotype.
B
Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells? a. Proto-oncogenes first arose from viral infections. b. Proto-oncogenes normally help regulate cell division. c. Proto-oncogenes are genetic "junk." d. Proto-oncogenes are mutant versions of normal genes. e. Cells produce proto-oncogenes as they age.
B
RNA viruses require their own supply of certain enzymes because a. host cells rapidly destroy the viruses. b. host cells lack enzymes that can replicate the viral genome. c. these enzymes translate viral mRNA into proteins. d. these enzymes penetrate host cell membranes. e. these enzymes cannot be made in host cells.
B
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 is a likely explanation? a. Use of adult stem cells is likely to produce more cell types than use of embryonic stem cells. b. Cloning to produce embryonic stem cells may lead to great medical benefits for many. c. Cloning to produce stem cells relies on a different initial procedure than reproductive cloning. d. A clone that lives until the blastocyst stage does not yet have human DNA. e. No embryos would be destroyed in the process of therapeutic cloning.
B
The comparison between the number of human genes and those of other animal species has led to many conclusions, including that a. the density of the human genome is far higher than in most other animals. b. the number of proteins expressed by the human genome is far more than the number of its genes. c. most human DNA consists of genes for protein, tRNA, rRNA, and miRNA. d. the genomes of other organisms are significantly smaller than the human genome.
B
Viral envelopes can best be analyzed with which of the following techniques? a. use of 15N to label specific nucleotides b. antibodies against specific proteins not found in the host membranes c. DNA staining and visualization with the light microscope d. use of plaque assays for quantitative measurement of viral titer e. immunofluorescent tagging of capsid proteins
B
What is bioinformatics? a. a technique using 3-D images of genes to predict how and when they will be expressed b. the application of computational methods to the storage and analysis of biological data c. software programs available from NIH to design and synthesize genes d. a series of search programs that allow a student to identify which labs around the world are trying to sequence the genome of a given species e. a procedure that uses software to order DNA sequences in a variety of comparable ways
B
What is considered to be the first evidence of differentiation in the cells of an embryo? a. cell division occurring after fertilization b. the occurrence of mRNAs for the production of tissue-specific proteins c. determination of specific cells for certain functions d. changes in the size and shape of the cell e. changes resulting from induction
B
What is proteomics? a. the linkage of each gene to a particular protein b. the study of the full protein set encoded by a genome c. the totality of the functional possibilities of a single protein d. the study of how amino acids are ordered in a protein e. the study of how a single gene activates many proteins
B
What is the function of reverse transcriptase in retroviruses? a. It hydrolyzes the host cell's DNA. b. It uses viral RNA as a template for DNA synthesis. c. It converts host cell RNA into viral DNA. d. It translates viral RNA into proteins. e. It uses viral RNA as a template for making complementary RNA strands.
B
When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by a. a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes. b. a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane. c. moving through a specialized channel of the nucleus. d. a chemical signal given off by the ER. e. a signal sequence of RNA that precedes the start codon of the message.
B
Which of the following can be effective in preventing the onset of viral infection in humans? a. taking vitamins b. getting vaccinated c. taking antibiotics d. applying antiseptics e. taking nucleoside analogs that inhibit transcription
B
Which of the following describes plant virus infections? a. They can be controlled by the use of antibiotics. b. They are spread via the plasmodesmata. c. They have little effect on plant growth. d. They are seldom spread by insects. e. They can never be passed vertically.
B
Which of the following genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo? a. homeotic genes b. segmentation genes c. egg-polarity genes d. morphogens e. inducers
B
Which of the following is true of transcription in domain Archaea? a. It is regulated in the same way as in domain Bacteria. b. There is only one kind of RNA polymerase. c. It produces RNA transcripts that are processed after they leave the nucleus. d. It involves promoters that are identical to those in domain Eukarya. e. It terminates in a manner similar to that in bacteria.
B
Which of the following would not be true of cDNA produced using human brain tissue as the starting material? a. It could be amplified by the polymerase chain reaction. b. It would contain sequences representing all the genes in the genome. c. It was produced from mRNA using reverse transcriptase. d. It could be used as a probe to detect genes expressed in the brain. e. It lacks the introns of the human genes.
B
Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator? a. ubiquitin b. inducer c. promoter d. repressor e. corepressor
B
A human pandemic is a. a viral disease that infects all humans. b. a flu that kills more than 1 million people. c. an epidemic that extends around the world. d. a viral disease that can infect multiple species. e. a virus that increases in mortality rate as it spreads.
C
A microarray known as a GeneChip, with most of the human protein-coding genetic sequences, has been developed to aid in the study of human cancer by first comparing two to three subsets of cancer subtypes. What kind of information might be gleaned from this GeneChip to aid in cancer prevention? a. information about whether or not a patient has this type of cancer prior to treatment b. evidence that might suggest how best to treat a person's cancer with chemotherapy c. data that could alert patients to what kind of cancer they were likely to acquire d. information about which parent might have provided a patient with cancer-causing genes e. information on cancer epidemiology in the United States or elsewhere
C
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate? a. The sequence evolves very rapidly. b. The sequence does not mutate. c. Any mutation in the sequence is selected against. d. The sequence is found in many but not all promoters. e. The sequence is transcribed at the start of every gene.
C
Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene a. is transcribed in the early embryo. b. normally leads to formation of tail structures. c. normally leads to formation of head structures. d. is a protein present in all head structures. e. leads to programmed cell death.
C
Bioinformatics includes all of the following except a. using computer programs to align DNA sequences. b. analyzing protein interactions in a species. c. using molecular biology to combine DNA from two different sources in a test tube. d. developing computer-based tools for genome analysis. e. using mathematical tools to make sense of biological systems.
C
During splicing, which molecular component of the spliceosome catalyzes the excision reaction? a. protein b. DNA c. RNA d. lipid e. sugar
C
In Figure 17.2, at the arrow marked II, what enzyme(s) are being utilized? a. reverse transcriptase b. viral DNA polymerase c. host cell DNA polymerase d. host cell RNA polymerase e. host cell DNA and RNA polymerases
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 the 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 e. utilization of eukaryotic polymerases
C
In order to determine the probable function of a particular sequence of DNA in humans, what might be the most reasonable approach? a. Prepare a knockout mouse without a copy of this sequence and examine the mouse phenotype. b. Genetically engineer a mouse with a copy of this sequence and examine its phenotype. c. Look for a reasonably identical sequence in another species, prepare a knockout of this sequence in that species, and look for the consequences. d. Prepare a genetically engineered bacterial culture with the sequence inserted and assess which new protein is synthesized. e. Mate two individuals heterozygous for the normal and mutated sequences.
C
Some viruses can be crystallized and their structures analyzed. One such virus is yellow mottle virus, which infects beans. This virus has a single-stranded RNA genome containing about 6,300 nucleotides. Its capsid is 25-30 nm in diameter and contains 180 identical capsomeres. If the yellow mottle virus capsid has 20 facets, how many proteins form each facet? a. 1 b. 5 c. 9 d. 20 e. 180
C
The nitrogenous base adenine is found in all members of which group? a. proteins, triglycerides, and testosterone b. proteins, ATP, and DNA c. ATP, RNA, and DNA d. α glucose, ATP, and DNA e. proteins, carbohydrates, and ATP
C
Tumor-suppressor genes a. are frequently over-expressed in cancerous cells. b. are cancer-causing genes introduced into cells by viruses. c. can encode proteins that promote DNA repair or cell-cell adhesion. d. often encode proteins that stimulate the cell cycle. e. do all of the above.
C
Two eukaryotic proteins have one domain in common but are otherwise very different. Which of the following processes is most likely to have contributed to this similarity? a. gene duplication b. alternative splicing c. exon shuffling d. histone modification e. random point mutations
C
Which of the following characteristics, structures, or processes is common to both bacteria and viruses? a. metabolism b. ribosomes c. genetic material composed of nucleic acid d. cell division e. independent existence
C
Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression? a. mRNA, tRNA, and rRNA are transcribed. b. RNA polymerase binds to the promoter. c. A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end. d. Transcription can begin as soon as translation has begun even a little. e. RNA polymerase requires a primer to elongate the molecule.
C
Which of the following is a representation of gene density? a. Humans have 2,900 Mb per genome. b. C. elegans has ~20,000 genes. c. Humans have ~20,000 genes in 2,900 Mb. d. Humans have 27,000 bp in introns. e. Fritillaria has a genome 40 times the size of a human genome.
C
Which of the following problems with animal cloning might result in premature death of the clones? a. use of pluripotent instead of totipotent stem cells b. use of nuclear DNA as well as mtDNA c. abnormal gene regulation due to variant methylation d. the indefinite replication of totipotent stem cells e. abnormal immune function due to bone marrow dysfunction
C
Which of the following statements describes the lysogenic cycle of lambda (λ) phage? a. After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses. b. Most of the prophage genes are activated by the product of a particular prophage gene. c. The phage genome replicates along with the host genome. d. Certain environmental triggers can cause the phage to exit the host genome, switching from the lytic to the lysogenic. e. The phage DNA is incorporated by crossing over into any nonspecific site on the host cell's DNA.
C
Which procedure is not required when the shotgun approach to sequencing is modified as sequencing by synthesis, in which many small fragments are sequenced simultaneously? a. use of restriction enzymes b. sequencing each fragment c. cloning each fragment into a plasmid d. ordering the sequences e. PCR amplification
C
You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious If you already knew that the infectious agent was either bacterial or viral, which treatment would allow you to distinguish between these two possibilities? a. I b. II c. III d. IV e. either II or IV
C
39. What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? a. irreversible binding of the repressor to the promoter b. reduced transcription of the operon's genes c. buildup of a substrate for the pathway controlled by the operon d. continuous transcription of the operon's genes e. overproduction of catabolite activator protein (CAP)
D
A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced will have a. T2 protein and T4 DNA. b. T2 protein and T2 DNA. c. a mixture of the DNA and proteins of both phages. d. T4 protein and T4 DNA. e. T4 protein and T2 DNA.
D
Apoptosis involves all but which of the following? a. fragmentation of the DNA b. cell-signaling pathways c. activation of cellular enzymes d. lysis of the cell e. digestion of cellular contents by scavenger cells
D
Emerging viruses arise by a. mutation of existing viruses. b. the spread of existing viruses to new host species. c. the spread of existing viruses more widely within their host species. d. all of the above e. none of the above
D
Figure 14.5 represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid? a. UGG b. GUG c. GUA d. UUC e. CAU
D
Figure 17.1 Which of the three types of viruses shown in Figure 17.1 would you expect to include glycoproteins? a. I only b. II only c. III only d. I and II only e. all three
D
Figure 18.2 shows a diagram of blocks of genes on human chromosome 16 and the locations of blocks of similar genes on four chromosomes of the mouse. The movement of these blocks suggests that a. during evolutionary time, these sequences have separated and have returned to their original positions. b. DNA sequences within these blocks have become increasingly divergent. c. sequences represented have duplicated at least three times. d. chromosomal translocations have moved blocks of sequences to other chromosomes. e. higher mammals have more convergence of gene sequences related in function.
D
In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA. Table 17.1 shows the results of testing five viruses (A—E) for nuclease specificity, the ability of the viral genome to act as an mRNA, and the presence (+) or absence (—) of each virus's own polymerase. Table 17.1 Based on Table 17.1, which virus meets the Baltimore requirements for a retrovirus? a. A b. B c. C d. D e. E
D
In 1997, Dolly the sheep was cloned. Which of the following processes was used? a. use of mitochondrial DNA from adult female cells of another ewe b. replication and dedifferentiation of adult stem cells from sheep bone marrow c. separation of an early-stage sheep blastula into separate cells, one of which was incubated in a surrogate ewe d. fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a surrogate e. isolation of stem cells from a lamb embryo and production of a zygote equivalent
D
In animals, what is the difference between reproductive cloning and therapeutic cloning? a. Reproductive cloning uses totipotent cells, whereas therapeutic cloning does not. b. Reproductive cloning uses embryonic stem cells, whereas therapeutic cloning does not. c. Therapeutic cloning uses nuclei of adult cells transplanted into enucleated nonfertilized eggs. d. Therapeutic cloning supplies cells for repair of diseased or injured organs.
D
Multigene families include two or more nearly identical genes or genes sharing nearly identical sequences. A classical example is the set of genes for globin molecules, including genes on human chromosomes 11 and 16. How might identical and obviously duplicated gene sequences have gotten from one chromosome to another? a. by normal meiotic recombination b. by normal mitotic recombination between sister chromatids c. by transcription followed by recombination d. by chromosomal translocation e. by deletion followed by insertion
D
Mutations in which of the following genes lead to transformations in the identity of entire body parts? a. morphogens b. segmentation genes c. egg-polarity genes d. homeotic genes e. inducers
D
The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur? a. The embryo would grow to an unusually large size. b. The embryo would grow extra wings and legs. c. The embryo would probably show no anterior development and die. d. Anterior structures would form in both sides of the embryo. e. The embryo would develop normally.
D
The first cloned cat, called Carbon Copy, was a calico, but she looked significantly different from her female parent. Why? a. The environment, as well as genetics, affects phenotypic variation. b. Fur color genes in cats are influenced by differential acetylation patterns. c. Cloned animals have been found to have a higher frequency of transposon activation. d. X inactivation in the embryo is random and produces different patterns. e. The telomeres of the parent's chromosomes were shorter than those of an embryo.
D
The herpes viruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones 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 three 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 then reactivate, replicate again, and be infectious to others. In electron micrographs of HSV infection, it can be seen that the intact virus initially reacts with cell-surface proteoglycans, then with specific receptors. This is later followed by viral capsids docking with nuclear pores. Afterward, the capsids go from being full to being "empty." Which of the following best fits these observations? a. Viral capsids are needed for the cell to become infected; only the capsids enter the nucleus. b. The viral envelope is not required for infectivity, since the envelope does not enter the nucleus. c. Only the genetic material of the virus is involved in the cell's infectivity, and is injected like the genome of a phage. d. The viral envelope mediates entry into the cell, the capsid enters into the nuclear membrane, and the genome is all that enters the nucleus. e. The viral capsid mediates entry into the cell, and only the genomic DNA enters the nucleus, where it may or may not replicate.
D
What is metagenomics? a. genomics as applied to a species that most typifies the average phenotype of its genus b. the sequence of one or two representative genes from several species c. the sequencing of only the most highly conserved genes in a lineage d. sequencing DNA from a group of species from the same ecosystem e. genomics as applied to an entire phylum
D
Which of the following statements describes proto-oncogenes? a. Their normal function is to suppress tumor growth. b. They are introduced to a cell initially by retroviruses. c. They are produced by somatic mutations induced by carcinogenic substances. d. They can code for proteins associated with cell growth. e. They are underexpressed in cancer cells.
D
Why might the cricket genome have 11 times as many base pairs as that of Drosophila melanogaster? a. The two insect species evolved in very different geologic eras. b. Crickets have higher gene density. c. Drosophila are more complex organisms. d. Crickets must have more noncoding DNA. e. Crickets must make many more proteins.
D
A frameshift mutation could result from a. a base insertion only. b. a base deletion only. c. a base substitution only. d. deletion of three consecutive bases. e. either an insertion or a deletion of a base.
E
Figure 18.1 Types of DNA sequences in the human genome. The pie chart in Figure 18.1 represents the relative frequencies of the following in the human genome: I. repetitive DNA unrelated to transposons II. repetitive DNA that includes transposons III. unique noncoding DNA IV. introns and regulatory sequences V. exons Which region includes Alu elements and LI sequences? a. A b. B c. C d. D e. E
E
In Figure 17.2, when new viruses are being assembled (IV), what mediates the assembly? a. host cell chaperones b. assembly proteins coded for by the host nucleus c. assembly proteins coded for by the viral genes d. viral RNA intermediates e. nothing; they self-assemble
E
Let us suppose that someone is successful at producing induced pluripotent stem cells (iPS) for replacement of pancreatic insulin-producing cells for people with type 1 diabetes. Which of the following could still be problematic? I. the possibility that, once introduced into the patient, the iPS cells produce nonpancreatic cells II. the failure of the iPS cells to take up residence in the pancreas III. the inability of the iPS cells to respond to appropriate regulatory signals a. I only b. II only c. III only d. I and II e. all of them
E
Most molecular biologists think that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory? a. Viruses contain either DNA or RNA. b. Viruses are enclosed in protein capsids rather than plasma membranes. c. Viruses can reproduce only inside host cells. d. Viruses can infect both prokaryotic and eukaryotic cells. e. Viral genomes are usually similar to the genome of the host cell.
E
The following questions refer to the table of codons in Figure 14.2. A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be a. 5' TTG-CTA-CAG-TAG 3'. b. 3' AAC-GAC-GUC-AUA 5'. c. 5' AUG-CTG-CAG-TAT 3'. d. 3' AAA-AAT-ATA-ACA 5'. e. 3' AAA-GAA-TAA-CAA 5'.
E
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 enzymes produced by the virus before it infects the cell. e. the proteins on its surface and that of the host.
E
The product of the bicoid gene in Drosophila provides essential information about a. lethal genes. b. the dorsal-ventral axis. c. the left-right axis. d. segmentation. e. the anterior-posterior axis.
E
The tryptophan operon is a repressible operon that is a. permanently turned on. b. turned on only when tryptophan is present in the growth medium. c. turned off only when glucose is present in the growth medium. d. turned on only when glucose is present in the growth medium. e. turned off whenever tryptophan is added to the growth medium.
E
Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' When the spliceosome binds to elements of this structure, where can it attach? a. to the exons b. to the 5' UTR c. to the 3' UTR d. to an adjacent intron and exon e. to the end of an intron
E
Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' When the spliceosome binds to this transcript, where can it attach? a. to the exons b. to the 5' UTR c. to the 3' UTR d. to an adjacent intron and exon e. at certain sites along an intron
E
Which of the following can be duplicated in a genome? a. DNA sequences above a minimum size only b. DNA sequences below a minimum size only c. entire chromosomes only d. entire sets of chromosomes only e. sequences, chromosomes, or sets of chromosomes
E
Which of the following is most closely identical to the formation of twins? a. cell cloning b. therapeutic cloning c. use of adult stem cells d. embryo transfer e. organismal cloning
E
Which of the following is the most probable fate of a newly emerging virus that causes high mortality in its host? a. It is able to spread to a large number of new hosts quickly because the new hosts have no immunological memory of them. b. The new virus replicates quickly and undergoes rapid adaptation to a series of divergent hosts. c. A change in environmental conditions such as weather patterns quickly forces the new virus to invade new areas. d. Sporadic outbreaks will be followed almost immediately by a widespread pandemic. e. The newly emerging virus will die out rather quickly or will mutate to be far less lethal.
E
Which of the following mutations would be most likely to have a harmful effect on an organism? a. a nucleotide-pair substitution b. a deletion of three nucleotides near the middle of a gene c. a single nucleotide deletion in the middle of an intron d. a single nucleotide deletion near the end of the coding sequence e. a single nucleotide insertion downstream of, and close to, the start of the coding sequence
E
Which of the following series best reflects what we know about how the flu virus moves between species? a. An avian flu virus undergoes several mutations and rearrangements such that it is able to be transmitted to other birds and then to humans. b. The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected. c. A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans. d. An influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host. e. An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates and is passed to a new species such as a bird, and the virus mutates and can be transmitted to humans.
E
Which of the three types of viruses shown in Figure 17.1 would you expect to include a capsid(s)? a. I only b. II only c. III only d. I and II only e. all three
E
Which viruses have single-stranded RNA that acts as a template for DNA synthesis? a. lytic phages b. proviruses c. viroids d. bacteriophages e. retroviruses
E
You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious If you already knew that the infectious agent was either a viroid or a prion, which treatment would allow you to distinguish between these two possibilities? a. I only b. II only c. III only d. IV only e. either I or IV
E
Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development? a. morphogenesis b. determination c. induction d. differentiation e. pattern formation
E
A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that a. many noncoding stretches of nucleotides are present in eukaryotic DNA. b. there is redundancy and ambiguity in the genetic code. c. many nucleotides are needed to code for each amino acid. d. nucleotides break off and are lost during the transcription process. e. there are termination exons near the beginning of mRNA.
A
A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Which of the following is a likely explanation for the lack of transgene expression in the fifth cell line? a. The transgene integrated into a heterochromatic region of the genome. b. The transgene integrated into a euchromatic region of the genome. c. The transgene was mutated during the process of integration into the host cell genome. d. The host cell lacks the enzymes necessary to express the transgene. e. The transgene integrated into a region of the genome characterized by high histone acetylation.
A
A mutation that inactivates the 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. inactivation of RNA polymerase by alteration of its active site. e. continuous translation of the mRNA because of alteration of its structure.
A
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is a. 3' UCA 5'. b. 3' UGA 5'. c. 5' TCA 3'. d. 3' ACU 5'. e. either UCA or TCA, depending on wobble in the first base.
A
Figure 15.1 In the microarray shown in Figure 15.1, if you were searching for genes whose expression was inhibited by hormone treatment, you would search for sequences spotted on the array that showed ________ fluorescence. a. no b. high levels of c. green d. red e. yellow
A
Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya? a. Domain Archaea has numerous transcription factors. b. Initiation of translation is like that of domain Eukarya. c. There is only one RNA polymerase. d. Transcription termination often involves attenuation. e. Post-transcriptional splicing is like that of Eukarya.
A
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. All organisms have experienced convergent evolution. c. DNA was the first genetic material. d. The same codons in different organisms translate into the different amino acids. e. Different organisms have different numbers of different types of amino acids.
A
When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? a. an assembled ribosome with a polypeptide attached to the tRNA in the P site b. separated ribosomal subunits, a polypeptide, and free tRNA c. an assembled ribosome with a separated polypeptide d. separated ribosomal subunits with a polypeptide attached to the tRNA e. a cell with fewer ribosomes
A
Which of the following best describes siRNA? a. a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA b. a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf patterns c. a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor d. a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits e. a molecule, known as Dicer, that can degrade other mRNA sequences
A
Which of the following is most likely to have a small protein called ubiquitin attached to it? a. a cyclin that usually acts in G1, now that the cell is in G2 b. a cell surface protein that requires transport from the ER c. an mRNA that is leaving the nucleus to be translated d. a regulatory protein that requires sugar residues to be attached e. an mRNA produced by an egg cell that will be retained until after fertilization
A
Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells? a. A specific combination of control elements in each gene's enhancer coordinates the simultaneous activation of the genes. b. The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time. c. The genes are organized into large operons, allowing them to be transcribed as a single unit. d. A single repressor is able to turn off several related genes. e. Environmental signals enter the cell and bind directly to promoters.
A
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. e. none of the options will occur; the cell will recognize the error and destroy the tRNA.
B
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments she succeeded in decreasing methylation of histone tails. Which of the following results would she most likely see? a. increased chromatin condensation b. decreased chromatin condensation c. activation of histone tails for enzymatic function d. decreased binding of transcription factors e. inactivation of the selected genes
B
Alternative RNA splicing a. is a mechanism for increasing the rate of transcription. b. can allow the production of proteins of different sizes and functions from a single mRNA. c. can allow the production of similar proteins from different RNAs. d. increases the rate of transcription. e. is due to the presence or absence of particular snRNPs.
B
Among the newly discovered small noncoding RNAs, one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons. These are known as a. miRNA. b. piRNA. c. snRNA. d. siRNA. e. RNAi.
B
Garrod's information about the enzyme alteration resulting in alkaptonuria led to further elucidation of the same pathway in humans. Phenylketonuria (PKU) occurs when another enzyme in the pathway is altered or missing, resulting in a failure of phenylalanine (phe) to be metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate in the pathway altered in alkaptonuria. How might PKU affect the presence or absence of alkaptonuria? a. It would have no effect, because PKU occurs several steps away in the pathway. b. It would have no effect, because tyrosine is also available from the diet. c. Anyone with PKU must also have alkaptonuria. d. Anyone with PKU is born with a predisposition to later alkaptonuria. e. Anyone with PKU has mild symptoms of alkaptonuria.
B
If a newly made polypeptide is to be secreted from a cell, what must occur before it is secreted? a. It must be translated by a ribosome that remains free of attachment to the ER. b. Its signal sequence must target it to the ER, after which it goes to the Golgi. c. Its signal sequence must be cleaved off before the polypeptide can enter the ER. d. Its signal sequence must target it to the plasma membrane, where it causes exocytosis. e. Its signal sequence must cause it to be encased in a vesicle as soon as it is translated.
B
In eukaryotes, general transcription factors a. are required for the expression of specific protein-encoding genes. b. bind to other proteins or to a sequence element within the promoter called the TATA box. c. inhibit RNA polymerase binding to the promoter and begin transcribing. d. usually lead to a high level of transcription even without additional specific transcription factors. e. bind to sequences just after the start site of transcription.
B
In eukaryotic cells, transcription cannot begin until a. the two DNA strands have completely separated and exposed the promoter. b. several transcription factors have bound to the promoter. c. the 5' caps are removed from the mRNA. d. the DNA introns are removed from the template. e. DNA nucleases have isolated the transcription unit.
B
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? a. increase in glucose and increase in cAMP b. decrease in glucose and increase in cAMP c. increase in glucose and decrease in cAMP d. decrease in glucose and increase in repressor e. decrease in glucose and decrease in repressor
B
In response to chemical signals, prokaryotes can do which of the following? a. turn off translation of their mRNA b. alter the level of production of various enzymes c. increase the number and responsiveness of their ribosomes d. inactivate their mRNA molecules e. alter the sequence of amino acids in certain proteins
B
RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such variability in RNA polymerase? a. It might allow the translation process to vary from one cell to another. b. It might allow the polymerase to recognize different promoters under certain environmental conditions. c. It could allow the polymerase to react differently to each stop codon. d. It could allow ribosomal subunits to assemble at faster rates. e. It could alter the rate of translation and of exon splicing.
B
The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following? a. polypeptide factors plus ATP b. polypeptide factors plus GTP c. polymerases plus GTP d. SRP plus chaperones e. signal peptides plus release factor
B
The tRNA shown in Figure 14.5 has its 3' end projecting beyond its 5' end. What will occur at this 3' end? a. The codon and anticodon complement one another. b. The amino acid binds covalently. c. The excess nucleotides (ACCA) will be cleaved off at the ribosome. d. The small and large subunits of the ribosome will attach to it. e. The 5' cap of the mRNA will become covalently bound.
B
There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that a. some tRNAs have anticodons that recognize four or more different codons. b. the rules for base pairing between the third base of a codon and tRNA are flexible. c. many codons are never used, so the tRNAs that recognize them are dispensable. d. the DNA codes for all 61 tRNAs but some are then destroyed. e. competitive exclusion forces some tRNAs to be destroyed by nucleases.
B
Which of the following is a protein produced by a regulatory gene? a. operon b. inducer c. promoter d. repressor e. corepressor
D
Transcription of the structural genes in an inducible operon a. occurs continuously in the cell. b. starts when the pathway's substrate is present. c. starts when the pathway's product is present. d. stops when the pathway's product is present. e. does not result in the production of enzymes.
B
Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might result? a. Removal of the 5' UTR has no effect because the exons are still maintained. b. Removal of the 5' UTR also removes the 5' cap, and the mRNA will quickly degrade. c. The 3' UTR will duplicate and one copy will replace the 5' end. d. The first exon will not be read because I1 will now serve as the UTR. e. Removal of the 5' UTR will result in the strand not binding to tRNAs.
B
Use the representation in Figure 14.3 to answer the following questions. In the transcription event of the previous DNA, where would the promoter be located? a. at the 3' end of the newly made RNA b. to the right of the template strand c. to the left of the template strand d. to the right of the sense strand e. to the left of the sense strand
B
What is a ribozyme? a. an enzyme that uses RNA as a substrate b. an RNA with enzymatic activity c. an enzyme that catalyzes the association between the large and small ribosomal subunits d. an enzyme that synthesizes RNA as part of the transcription process e. an enzyme that synthesizes RNA primers during DNA replication
B
What is the function of the release factor (RF)? a. It separates tRNA in the A site from the growing polypeptide. b. It binds to the stop codon in the A site in place of a tRNA. c. It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond. d. It supplies a source of energy for termination of translation. e. It releases the ribosome from the ER to allow polypeptides into the cytosol.
B
When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity? a. DNA supercoiling at or around H1 b. methylation and phosphorylation of histone tails c. hydrolysis of DNA molecules where they are wrapped around the nucleosome core d. accessibility of heterochromatin to phosphorylating enzymes e. nucleotide excision and reconstruction
B
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. RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript. d. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. e. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA.
B
Which of the following statements is true about protein synthesis in prokaryotes? a. Extensive RNA processing is required before prokaryotic transcripts can be translated. b. Translation can begin while transcription is still in progress. c. Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles. d. Translation requires antibiotic activity. e. Unlike eukaryotes, prokaryotes require no initiation or elongation factors.
B
Which one of the following techniques involves reverse transcriptase, PCR amplification, and gel electrophoresis? a. DNA microarray assays b. RT-PCR c. in situ hybridization d. RNA interference e. nucleic acid hybridization
B
Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein? a. a base substitution b. a base deletion near the start of a gene c. a base deletion near the end of the coding sequence, but not in the terminator codon d. deletion of three bases near the start of the coding sequence, but not in the initiator codon e. a base insertion near the end of the coding sequence, but not in the terminator codon
B
You are given an experimental problem involving control of a gene's expression in the embryo of a particular species. One of your first questions is whether the gene's expression is controlled at the level of transcription or translation. Which of the following might best give you an answer? a. You explore whether there has been alternative splicing by examining amino acid sequences of very similar proteins. b. You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same. c. You assess the position and sequence of the promoter and enhancer for this gene. d. An analysis of amino acid production by the cell shows you that there is an increase at this stage of embryonic life. e. You use an antibiotic known to prevent translation.
B
n one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see? a. increased chromatin condensation b. decreased chromatin condensation c. activation of histone tails for enzymatic function d. decreased binding of transcription factors e. inactivation of the selected genes
B
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. e. either UAA or TAA, depending on first base wobble.
C
A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) already in the ribosome. Where does tRNA #2 move to after this bonding of lysine to the polypeptide? a. A site b. P site c. E site d. exit tunnel e. directly to the cytosol
C
Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways? 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 the organism to adjust to changes in environmental conditions d. allowing young organisms to respond differently from more mature organisms e. allowing environmental changes to alter the prokaryote's genome
C
An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result? a. tRNA will not form a cloverleaf. b. The nearby stem end will pair improperly. c. The amino acid methionine will not become covalently bound. d. The anticodon will not bind with the mRNA codon. e. The aminoacyl-tRNA synthetase will not be formed.
C
During DNA replication, a. all methylation of the DNA is lost at the first round of replication. b. DNA polymerase is blocked by methyl groups, and methylated regions of the genome are therefore left uncopied. c. methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylates daughter strands after replication. d. methylation of the DNA is maintained because DNA polymerase directly incorporates methylated nucleotides into the new strand opposite any methylated nucleotides in the template. e. methylated DNA is copied in the cytoplasm, and unmethylated DNA is copied in the nucleus.
C
Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following? a. Eukaryotic mRNAs get 5' caps and 3' tails. b. Prokaryotic genes are expressed as mRNA, which is more stable in the cell. c. Eukaryotic exons may be spliced in alternative patterns. d. Prokaryotes use ribosomes of different structure and size. e. Eukaryotic coded polypeptides often require cleaving of signal sequences before localization.
C
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? a. ligase b. RNA polymerase I c. RNA polymerase II d. RNA polymerase III e. primase
C
In order for a eukaryotic gene to be engineered into a bacterial colony to be expressed, what must be included in addition to the coding exons of the gene? a. the introns b. eukaryotic polymerases c. a bacterial promoter sequence d. eukaryotic ribosomal subunits e. eukaryotic tRNAs
C
One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs? a. exploring a way to turn on the expression of pseudogenes b. targeting siRNAs to disable the expression of an allele associated with autosomal recessive disease c. targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease d. creating knock-out organisms that can be useful for pharmaceutical drug design e. looking for a way to prevent viral DNA from causing infection in humans
C
Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying leucine, Leu). What will be the effect on translation in this cell? a. The altered tRNA will cause this mRNA to make only nonfunctioning product. b. The tRNA-Leu will not be able to enter the ribosome to bind to the UUA codon. c. One altered tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones. d. The altered tRNA will be so unstable that it will not participate in translation. e. The altered tRNA will result in an amino acid variant in all copies of the protein.
C
The following questions refer to the simple metabolic pathway in Figure 14.1. If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on which of the following media? a. minimal medium b. minimal medium supplemented with nutrient A only c. minimal medium supplemented with nutrient B only d. minimal medium supplemented with nutrient C only e. minimal medium supplemented with nutrients A and C
C
The following questions refer to the table of codons in Figure 14.2. A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA could code for this peptide? a. 3' UUU-CCC-AAA-GGG-UUU-CCC b. 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG c. 5' TTT-CCC-AAA-GGG-TTT-CCC d. 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG e. 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA
C
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? a. It cannot bind to the operator. b. It cannot make a functional repressor. c. It cannot bind to the inducer. d. It makes molecules that bind to one another. e. It makes a repressor that binds CAP.
C
Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Which components of the previous molecule will also be found in mRNA in the cytosol? a. 5' UTR I1 I2 I3 UTR 3' b. 5' E1 E2 E3 E4 3' c. 5' UTR E1 E2 E3 E4 UTR 3' d. 5' I1 I2 I3 3' e. 5' E1 I1 E2 I2 E3 I3 E4 3'
C
What is the effect of a nonsense mutation in a gene? a. It changes an amino acid in the encoded protein. b. It has no effect on the amino acid sequence of the encoded protein. c. It introduces a premature stop codon into the mRNA. d. It alters the reading frame of the mRNA. e It prevents introns from being excised.
C
Which of the following is an example of post-transcriptional control of gene expression? a. the addition of methyl groups to cytosine bases of DNA b. the binding of transcription factors to a promoter c. the removal of introns and alternative splicing of exons d. the binding of RNA polymerase to transcription factors e. the folding of DNA to form heterochromatin
C
At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. There was surprise expressed by many that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for most of the rest? a. "junk" DNA that serves no possible purpose b. rRNA and tRNA coding sequences c. DNA that is translated directly without being transcribed d. non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function e. non-protein-coding DNA that is transcribed into several kinds of small RNAs without biological function
D
If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then a. the amino acid inactivates the repressor. b. the enzymes produced are called inducible enzymes. c. the repressor is active in the absence of the amino acid. d. the amino acid acts as a corepressor. e. the amino acid turns on transcription of the operon.
D
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? a. The inducer will no longer bind to the repressor. b. The repressor will no longer bind to the operator. c. The operon will never be transcribed. d. The structural genes will be transcribed continuously. e. The repressor protein will no longer be produced.
D
In a genome-wide expression study using a DNA microarray assay, each well is used to detect the a. fate of proteins produced by a cell. b. location of a protein produced by a cell. c. location of a gene within a cell. d. expression of a specific gene by a cell. e. type of chemical modification of proteins produced by a cell.
D
In the 1920s, Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals—she used nitrogen mustards—have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation? a. We worry that it might cause mutation in cereal grain plants. b. We want to make sure that it does not emit radiation. c. We want to be sure that it increases the rate of mutation sufficiently. d. We want to prevent any increase in mutation frequency. e. We worry about its ability to cause infection.
D
Steroid hormones produce their effects in cells by a. activating key enzymes in metabolic pathways. b. activating translation of certain mRNAs. c. promoting the degradation of specific mRNAs. d. binding to intracellular receptors and promoting transcription of specific genes. e. promoting the formation of looped domains in certain regions of DNA.
D
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? a. The three structural genes will be expressed normally. b. RNA polymerase will no longer transcribe permease. c. The operon will no longer be inducible. d. Beta galactosidase will not be produced. e. The cell will continue to metabolize but more slowly.
D
The following questions refer to the simple metabolic pathway in Figure 14.1. If A, B, and C are all required for growth, a strain mutant for the gene-encoding enzyme B would be capable of growing on which of the following media? a. minimal medium b. minimal medium supplemented with A only c. minimal medium supplemented with B only d. minimal medium supplemented with C only e. minimal medium supplemented with nutrients A and B
D
The following questions refer to the table of codons in Figure 14.2. What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3' a. met-arg-glu-arg-glu-arg b. met-glu-arg-arg-glu-leu c. met-ser-leu-ser-leu-ser d. met-ser-ser-leu-ser-leu e. met-leu-phe-arg-glu-glu
D
The lactose operon is likely to be transcribed when a. there is more glucose in the cell than lactose. b. the cyclic AMP levels are low. c. there is glucose but no lactose in the cell. d. the cyclic AMP and lactose levels are both high within the cell. e. the cAMP level is high and the lactose level is low.
D
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in a. a base-pair substitution. b. a nucleotide mismatch. c. a frameshift mutation. d. a polypeptide missing an amino acid. e. a nonsense mutation.
D
Transcription factors in eukaryotes usually have DNA binding domains as well as other domains that are also specific for binding. In general, which of the following would you expect many of them to be able to bind? a. repressors b. ATP c. protein-based hormones d. other transcription factors e. tRNA
D
Two potential devices that eukaryotic cells use to regulate transcription are a. DNA methylation and histone amplification. b. DNA amplification and histone methylation. c. DNA acetylation and methylation. d. DNA methylation and histone modification. e. histone amplification and DNA acetylation.
D
Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Suppose that exposure to a chemical mutagen results in a change in the sequence that alters the 5' end of intron 1 (I1). What might occur? a. loss of the gene product b. loss of E1 c. premature stop to the mRNA d. inclusion of I1 in the mRNA e. exclusion of E2
D
Using the following figure, identify a 5' → 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys. a. 5´-UUUGGGAAA-3' b. 5´-GAACCCCTT-3' c. 5´-AAAACCTTT-3' d. 5´-CTTCGGGAA-3' e. 5´-AAACCCUUU-3'
D
When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply? a. There are 20,000 genes. b. Each gene codes for one protein. c. Any other regions are "junk" DNA. d. There are also genes for RNAs other than mRNA. e. The species is highly evolved.
D
Which of the following is a function of a signal peptide? a. to direct an mRNA molecule into the cisternal space of the ER b. to bind RNA polymerase to DNA and initiate transcription c. to terminate translation of the messenger RNA d. to translocate polypeptides across the ER membrane e. to signal the initiation of transcription
D
Which of the following is not true of a codon? a. It consists of three nucleotides. b. It may code for the same amino acid as another codon. c. It never codes for more than one amino acid. d. It extends from one end of a tRNA molecule. e. It is the basic unit of the genetic code.
D
Which of the following mutations is most likely to cause a phenotypic change? a. a duplication of all or most introns b. a large inversion whose ends are each in the same region between genes c. a nucleotide substitution in an exon coding for a transmembrane domain d. a single nucleotide deletion in an exon coding for an active site e. a frameshift mutation one codon away from the 3' end of the nontemplate strand
D
Which of the following nucleotide triplets best represents a codon? a. a triplet separated spatially from other triplets b. a triplet that has no corresponding amino acid c. a triplet at the opposite end of tRNA from the attachment site of the amino acid d. a triplet in the same reading frame as an upstream AUG e. a sequence in tRNA at the 3' end
D
Which of the following provides some evidence that RNA probably evolved before DNA? a. RNA polymerase uses DNA as a template. b. RNA polymerase makes a single-stranded molecule. c. RNA polymerase does not require localized unwinding of the DNA. d. DNA polymerase uses primer, usually made of RNA. e. DNA polymerase has proofreading function.
D
Why might a point mutation in DNA make a difference in the level of a protein's activity? a. It might result in a chromosomal translocation. b. It might exchange one stop codon for another stop codon. c. It might exchange one serine codon for a different serine codon. d. It might substitute a different amino acid in the active site. e. It might substitute the N-terminus of the polypeptide for the C-terminus.
D
n an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find? a. The mRNA could not exit the nucleus to be translated. b. The cell recognizes the absence of the tail and polyadenylates the mRNA. c. The molecule is digested by restriction enzymes in the nucleus. d. The molecule is digested by exonucleases because it is no longer protected at the 5' end. e. The molecule attaches to a ribosome and is translated, but more slowly.
D
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. shape of the A and P sites of ribosomes. c. bonding of the anticodon to the codon. d. attachment of amino acids to tRNAs. e. bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.
E
Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because a. metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. b. enzymes are made of DNA, and affected individuals lack DNA polymerase. c. many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA. d. certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. e. genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
E
If she moves the repressor gene (lac I), along with its promoter, to a position some several thousand base pairs away from its normal position, which will you expect to occur? a. The repressor will no longer be made. b. The repressor will no longer bind to the operator. c. The repressor will no longer bind to the inducer. d. The lac operon will be expressed continuously. e. The lac operon will function normally.
E
