BIO 203 Exam 4 Practice Questions – Flashcards
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What is the reason that closely linked genes are typically inherited together? A) chromosomes are unbreakable B) the number of genes in a cell is greater than the number of chromosomes C) genes align that way during metaphase I of meiosis D) the likelihood of a crossover event between these two genes is low E) alleles are paired together during meiosis
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D
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All female mammals have one active X chromosome per cell instead of two. What causes this? A) inactivation of the SRY gene on the X chromosome derived from the male parent B) attachment of methyl (CH3) groups to the X chromosome that will remain active C) activation of the XIST gene on the X chromosome that will become the Barr body D) activation of the SRY gene on one X chromosome, which then becomes inactive E) crossing over between the SRY gene on one X chromosome and a related gene on an autosome
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C
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In his transformation experiments, what did Griffith observe? A) mice infected with a pathogenic strain of bacteria can spread the infection to other mice B) Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains C) Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form D) Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic E) Mutant mice were resistant to bacterial infections
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C
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In trying to determine whether DNA or protein is the genetic material of phage using radioisotopes, Hershey and Chase made use of which of the following facts? A) DNA contains purines, whereas protein includes pyrimidines B) DNA contains sulfur, whereas protein does not C) DNA contains phosphorus, whereas protein does not D) RNA includes ribose, whereas DNA includes deoxyribose sugars E) DNA contains nitrogen, whereas protein does not
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C
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Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments? A) only short DNA sequences can extend off the RNA primers B) the replication forks block the formation of longer strands C) DNA polymerase can assemble DNA only in the 5' to 3' direction D) DNA polymerase can assemble DNA only in the 3' to 5' direction E) it is more efficient than assembling complete new strands
answer
C
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Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine? A) 42% B) 16% C) 8% D) 31% E) It cannot be determined from the information provided.
answer
C
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DNA replication is said to be semiconservative. What does this mean? A) one strand of the new double helix is made of DNA and the other strand is made of RNA B) half of the old strand is degraded and half is used as a template for the replication of a new strand C) the old double helix is degraded and half of its nucleotides are used in the construction of two new double helices D) one of the two resulting double helices is made of two old strands, and the other is made of two new strands E) each new double helix consists of one old and one new strand
answer
E
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What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called? A) Okazaki fragments B) origins of replication C) supercoiled DNA D) centromeres E) none of the above
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E Correct answer: telomeres
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A particular triplet of bases in the template strand of DNA is 5' CTA 3'. The corresponding codon for the mRNA transcribed is A) 5' TCA 3' B) 3' UGA 5' C) 3' GAU 5' D) 3' ACU 5' E) either UCA or TCA, depending on wobble in the first base
answer
C
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At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T C G A A T G G 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence? A) 5' G C C T A G G 3' B) 5' A G C U U A C C 3' C) 5' G C C U A G G 3' D) 3' G C C T A G G 5' E) 5' A C G T T A G G 3'
answer
B
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Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the A) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs B) binding of transcription factors to mRNA C) TATA box D) poly-A tail E) signal peptide
answer
A
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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) the ribosome will skip a codon every time a UUU is encountered B) the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons C) none of the proteins in the cell will contain phenylalanine D) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU E) none of the options will occur; the cell will recognize the error and destroy the tRNA
answer
D
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When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by A) a signal sequence of RNA that precedes the start codon of the message B) a chemical signal given off by the ER C) a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane D) a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes E) moving through a specialized channel of the nucleus
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C
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Which of the following DNA mutations is the least likely to be damaging to the protein it specifies? A) a substitution in the last base of a codon B) a base-pair deletion C) a point mutation D) a codon deletion E) a frameshift mutation
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A
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The figure below demonstrates the outcome of the following type of mutation: A) frameshift causing extensive missense B) missense mutation C) silent mutation D) frameshift causing nonsense mutation E) none of the above
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A
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Which of the following does not occur in prokaryotic gene expression, but does in eukaryotic gene expression? A) RNA polymerase requires a primer to elongate the molecule B) RNA polymerase binds to the promoter C) mRNA, tRNA, and rRNA are transcribed D) transcription can begin as soon as translation has begun even a little E) none of the above
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E Correct answer: A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.
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The average length of a transcription unit along a eukaryotic DNA molecule is about 27kb nucleotide pairs, whereas an averaged- sized protein is about 400 amino acids long. What is the best explanation for this fact? A) each amino acid in a protein is encoded by a triplet of nucleotides B) many genes are subject to alternative RNA splicing C) most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated D) DNA undergoes extensive rearrangements prior to transcription E) none of the above
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C
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The tryptophan operon is a repressible operon that is A) permanently turned on B) turned on only when glucose is present in the growth medium C) turned off whenever tryptophan is added to the growth medium D) turned off only when glucose is present in the growth medium E) turned on only when tryptophan is present in the growth medium
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C
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If you were to observe the activity of methylated DNA, you would expect it to A) be very actively transcribed and translated B) have turned off or slowed down the process of transcription C) be replicating nearly continuously D) be unwinding in preparation for protein synthesis E) induce protein synthesis by not allowing repressors to bind to it
answer
B
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In eukaryotes, general transcription factors A) bind to other proteins or to a sequence element within the promoter called the TATA box B) bind to sequences just after the start site of transcription C) bind to mRNA and stimulate translation D) inhibit RNA polymerase binding to the promoter and begin transcribing E) none of the above
answer
A
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Which of the following best describes siRNA? A) an RNA that acts as a primer for DNA synthesis B) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits C) a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA D) a ribozyme E) a molecule, known as Dicer, that can degrade other mRNA sequences
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C
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The product of the bicoid gene in Drosophila provides essential information about A) segmentation B) lethal genes C) muscle cell differentiation D) the anterior-posterior axis E) wing development
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D
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Which of the following statements describes proto-oncogenes? A) They are cellular genes responsible for normal cell growth and division B) They repair damaged DNA C) They are cancer-causing genes D) They are introduced to a cell initially by retroviruses E) They are produced by somatic mutations induced by carcinogenic substances
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A
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A student wants to clone a DNA sequence of ~200 kb in length. Which vector would be appropriate? A) a bacteriophage B) a large polypeptide C) a plant virus D) a plasmid E) none of the above
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E Correct answer: a BAC
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Mutations in the ras gene may lead to A) DNA repair B) production of a hyperactive Ras protein and increased cell division C) cell-cell adhesion D) prevent of the cell cycle E) none of the above
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B
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BRCA1 and BRCA2 are considered to be tumor-suppressor genes because A) the mutant forms of either one of these prevent breast cancer B) the normal genes lead to production of a hyperactive Ras protein C) they block penetration of breast cells by chemical carcinogens D) they prevent infection by tumor viruses that cause cancer E) their normal products participate in repair of DNA damage
answer
E
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Genomic imprinting, DNA methylation, and histone acetylation are all examples of A) karyotypes B) translocation C) chromosomal rearrangements D) epigenetic phenomena E) genetic mutation
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D
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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 splicing B) epigenetics C) RNA interference D) positive gene regulation E) none of the above
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C
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The following enzyme is necessary to generate a complementary DNA library: A) complementarase B) reverse complementarase C) librase D) restriction enzyme E) none of the above
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E Correct answer: reverse transcriptase and/or DNA ligase
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Agent Scully was able to complete the following technique (in under two hours) combining gel electrophoresis of DNA fragments with nucleic acid hybridization in order to demonstrate the existence of alien DNA which had integrated into her own DNA A) Eastern blot B) Southern blot C) polymerase chain reaction D) restriction fragment length polymorphism E) none of the above
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B
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Scientists can utilize the following techniques in order to get DNA inside a target cell: A) electroporation B) electrocution C) electromagnetic waves D) static electricity E) having an electrifying personality
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A
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The following technique requires heating, cooling, and replication in order to bring about a chain reaction that produces an exponentially growing population of identical DNA molecules A) Southern blot B) DNA microarray C) Western blot D) Northern blot E) polymerase chain reaction
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E
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A gene that contains introns can be made shorter (but remain functional) for genetic engineering purposes by using A) RNA polymerase to transcribe the gene B) reverse transcriptase to reconstruct the gene from its mRNA C) DNA polymerase to reconstruct the gene from its polypeptide product D) a restriction enzyme to cut the gene into shorter pieces E) DNA ligase to put together fragments of the DNA that code for a particular polypeptide
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B
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In order to insert a human gene into a plasmid, both must A) have identical DNA sequences B) originate from the same type of cell C) code for the same gene product D) be cut by the same restriction enzyme E) be the same length
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D
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Which of the following is true of embryonic stem cells but not of adult stem cells? A) One aim of using them is to provide cells for repair of diseased tissue B) They can provide enormous amounts of information about the process of gene regulation C) They normally differentiate into only eggs and sperm D) They can continue to reproduce for an indefinite period E) They can give rise to all cell types in the organism
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E
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Cold case detectives are investigating a homicide that took place 30 years ago. In reexamining the evidence, they find a tiny spot of blood on the victim's clothing that was likely left by the murderer. The DNA in the blood has partially degraded over time. What technique would the blood lab technicians use in their examination of this tiny, degraded blood sample? A) restriction enzyme digest and DNA ligase to make recombinant DNA from this sample B) Southern blot analysis C) polymerase chain reaction to amplify the DNA D) DNA microarray analysis E) none of the above
answer
C
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DNA microarrays have made a huge impact on genomic studies because they A) can be used to eliminate the function of any gene in the genome B) allow the expression of many or even all of the genes in the genome to be compared at once C) allow physical maps of the genome to be assembled in a very short time D) dramatically enhance the efficiency of restriction enzymes E) can be used to introduce entire genomes into bacterial cells
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B
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Relatively short DNA fragments can be sequenced using A) reverse transcriptase B) dideoxyribonucleotides tagged with a distinct fluorescent label C) a fluorescently labeled probe D) siRNA E) none of the above
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B
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What methodology is normally utilized to insert a cloned gene into bone marrow cells from patients to correct a defective gene? A) infection with a retrovirus carrying the RNA version of the normal gene B) a BAC C) in vitro mutagenesis D) in situ hybridization E) none of the above
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A
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Gene function can be determined by disabling the gene using A) in vitro mutagenesis B) reverse transcriptase- polymerase chain reaction C) in situ hybridization D) nuclear transplantation E) none of the above
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A
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Dr. Feuer would like to clone himself so that he can go surfing while his clone teaches BIOL 203. In the end, Dr. Feuer decides against this foolish plan for the following reasons: A) ethical and moral considerations B) telomere shortening may contribute to disease if the donor nucleus is removed from somatic cells for cloning purposes C) only a small percentage of cloned embryos have developed normally to birth most likely since epigenetic changes must be reversed in the donor nucleus D) Dr. Feuer is concerned that his clone may be a better surfer than himself E) all of the above
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E
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Which of the following is one of the technical reasons why gene therapy is problematic? A) Cells with transferred genes are unlikely to replicate B) Most cells with engineered genes overwhelm other cells in a tissue C) Transferred genes may not have appropriately controlled activity D) Most cells with an engineered gene do not produce gene product E) mRNA from transferred genes cannot be translated
answer
C
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Transcription of the structural genes in an inducible operon A) starts when the pathway's product is present B) occurs continuously in the cell C) does not result in the production of enzymes D) starts when the pathway's substrate is present E) stops when the pathway's product is present
answer
D
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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) certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. C) many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA. D) enzymes are made of DNA, and affected individuals lack DNA polymerase. E) genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
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E
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A student wants to clone a DNA sequence of ~200 kb in length. Which vector would be appropriate? A) a bacteriophage B) a large polypeptide C) a plant virus D) a BAC E) a plasmid
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D
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A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is A) 5' TCA 3' B) 3' UCA 5' C) 3' UGA 5' D) 3' ACU 5' E) either UCA or TCA, depending on wobble in the first base
answer
B
