Biology Expert Answers & Study Resources

52) Describe a toeprint assay involving mammalian ribosomal subunits and a mRNA in a cell-free extract that contains all the factors necessary for translation. (a) What results would you expect to see with 40S ribosomal subunits alone? (b) With 60S subunits alone? (c) With both subunits and all amino acids except serine, which.

92) You are investigating a gene with two large introns (intron 1 and 2) and three short exons (exons A, B, C). Show the results of R-looping experiments performed with: (a) mRNA with exons A, B, and C, and single-stranded DNA (b) pre-mRNA and single-stranded DNA (c) mRNA with exons A and C.

16) Transfer RNAs are thought to improve the fidelity of mRNA translation by A. preventing translocation if an incorrect amino acid is present in the peptidyl transferase center. B. increasing the rate of GTP hydrolysis by EF-Tu upon accurate codon-anticodon pairing. C. activating proofreading activity of eEF2. D. linking codon-anticodon mispairing in the P.

98) The results of the experiment shown in Fig. 13.34 suggest that miRNAs play a role in the tissue-specific suppression of certain genes during development. Propose an experiment to follow up on these studies. For example, when does suppression by miR-1 and miR-124 occur naturally? 99) What is the likely fate.

11) What would be the consequence of inactivation of the E2F complex? A. Cells would be unable to enter the S phase of the cell cycle. B. Cells would immediately enter the S phase of the cell cycle. C. Cells would rapidly proliferate and form a tumor. D. The retinoblastoma protein (pRB) would become.

65) As they light up their cigarette, a friend of yours tells you that they have heard that benzo(a)pyrene in cigarette smoke is not really a carcinogen. Set them straight. 66) You are designing a somatic cell gene therapy protocol for spinal muscular atrophy, a genetic disorder that is caused by.

1) Which component is not directly involved in the process known as translation? A. mRNA B. tRNA C. rRNA D. DNA 2) Which statement is not true about the nucleolus? A. The nucleolus is the site of rRNA synthesis. B. The nucleolus is a membrane-bound organelle within the nucleus. C. The nucleolus is the site of ribosome subunit.

55) A skeptic thinks that only proteins can be enzymes. Provide X-ray crystallographic and biochemical evidence in support of the view that the ribosome is a ribozyme. .

6) In establishing paternity by DNA typing, how many short tandem repeat (STR) alleles in a child come from the father? A. ¼ B. ½ C. ¾ D. none 7) At approximately 2 PM; Ms. Smith, Ms. Taylor, and Ms. Jones each delivered a healthy baby girl at a local hospital. At 2:16 PM, the.

53) After sequencing the entire genome of a novel organism by the whole-genome shotgun approach, you use a computer program to search for start/stop signals for translation and homology searches based on similarity to cDNAs in the database. You predict approximately 20,000 genes. Is this an accurate representation of the.

6) You have received a lineage of “knockout mice” from a collaborator. What method would not be useful to confirm that the mice really do not express the targeted gene in all tissues of the body? A. Northern blot B. Neomycin sensitivity assay C. Western blot D. Reverse transcriptase-PCR 7) Gene knockouts often result in.

31) Retrovirus vectors for gene therapy have all of the following characteristics except: A. they can infect both dividing and nondividing cells. B. they have a limited insert size. C. they have generate only a mild immune response D. they stably integrate into host chromosomes 32) Which mode of gene therapy accomplishes transgene integration into.

1) Which statement is not true about cancer? A. Cancer results from the accumulation of many genetic changes. B. Gene mutations that increase the risk for developing cancer are always inherited. C. Cancer cells grow in an uncontrolled and invasive way. D. Cancer cells are immortal. 2) The process by which cancer cells travel from.

37) What would be the outcome if the procedure used to make gene-targeted (knock-out) mice was altered in the following ways (consider each situation separately). (a) The embryo-derived stem (ES) cells did not possess a gene responsible for visible phenotypic trait (such as agouti coat color) that differed from that of.

42) Describe the original observations that indicated the existence of “split genes.” 65) Besides base-pairing with the pre-mRNA, U6 base-pairs with two snRNAs. Which ones are they? 83) You discover that a single gene can produce two different proteins. Provide possible explanations for your observation. .

11) What distinguishes the field of genomics from genetics? A. Genomics deals with genomes; genetics deals with gene products. B. A goal of genomics is to understand how genes influence both genotype and phenotype; genetics only considers how genes influence phenotype. C. Genomics is based almost solely on studies of human genome sequences;.

11) Hydrolysis of ATP indirectly fuels protein synthesis by A. generating a high energy bond between the amino acid and tRNA. B. loading the ternary complex onto the 40S subunit. C. triggering translocation of the mRNA within the ribosome during elongation. D. triggering dissociation of the large and small ribosomal subunits at termination so.

31) Which component of the nucleolus is thought to be the location of active ribosomal genes? 32) An active ribosomal RNA gene has a “Christmas tree” structure as visualized by electron microscopy. What are the “branches” and what is the “trunk”? .

6) What is a tumor suppressor gene? A. A gene associated with tumor formation when its product does not function. B. A gene associated with tumor formation when its product functions normally. C. A gene that accelerates the cell cycle and leads to uncontrolled cell growth. D. A gene that codes for a transcription.

38) Consider the following hypothetical scenario: A young scientific genius, Dolly, is terminally ill with hereditary nonpolyposis colon cancer (HNPCC). When she dies, her parents feel that one of the most remarkable minds in science will die with her, and they feel they owe it to the world to not let.

6) What is an anticodon? A. The base sequence of an mRNA that signals the termination of translation. B. The base sequence of an mRNA that binds to a complementary codon in tRNA. C. The base sequence of a tRNA that binds to a complementary codon in mRNA. D. The base sequence of a.

48) How could DNA microarrays be used in conducting a genome-wide association study to identify SNPs associated with, e.g., type II diabetes? 50) A cigarette butt found at the scene of a violent crime is found to have a sufficient number of epithelial cells stuck to the paper for the.

39) A team of molecular biologists seeks your advice regarding whether it would be more important to include regulatory elements such as insulators and matrix attachment regions in a gene construct for generating transgenic mice by gene-targeting in embryo-derived stem cells, or for generating transgenic mice by microinjection of foreign.

36) Design a Southern blot experiment to check a transgenic mouse’s DNA for integration of the GFP cDNA under control of a constitutive promoter. You many assume any array of restriction sites you wish in the target mouse chromosome and in the GFP transgene. (a) Show sample results for a.

11) All of the following are true of stem cells except: A. They can be found in many developing organs. B. They are terminally differentiated. C. They have a high replicative capacity. D. They may differentiate to replace cells lost to injury. 12) When cloning an organism by nuclear transfer A. there is random integration.

36) The targets of a microRNA are usually A. viral mRNAs B. bacterial dsRNAs C. tissue-specific genes D. “housekeeping” genes 37) The nuclear exosome A. degrades aberrant mRNAs B. cleaves dsRNA into siRNAs C. promotes nuclear export of mature mRNA complexes D. facilitates spliceosome assembly 38) Which aspect of an mRNA’s life cycle serves as a key mRNA quality.

26) Currently, somatic cell gene therapy: A. has only been tested in cell culture and animal models B. is experimental and has never achieved any clinical success. C. is experimental and has achieved only very limited clinical success. D. is routine and has been used successfully to treat many diseases. 27) With respect to gene.

21) Which technique has almost eliminated the need to chemically sequence a polypeptide? A. peptide mass fingerprinting using MALDI-TOF B. functional protein array C. DNA microarray D. whole-genome shotgun sequencing 22) You want to analyze the entire proteome of a particular organelle. Which technique would you use? A. DNA microarray B. tandem mass spectrometry C. Western blot D. analytical.

61) Can gene therapy be used for purposes other than treatment of “monogenic” diseases (e.g., cystic fibrosis)? Explain your answer. 62) You suspect that a gene you have cloned is a proto-oncogene. Describe how you would test your hypothesis experimentally. Predict the results. .

26) For some pre-mRNAs, splicing is regulated by A. RNA polymerase stalling B. splicing enhancer sequences C. localization of the pre-mRNA to subnuclear “speckles” D. transcription termination 27) When an exon from one pre-mRNA joins to an exon from another pre-mRNA the process is called A. trans-splicing B. cis-splicing C. alternative splicing D. RNA editing 28) RNA editing is a.

21) Which step of translation requires mRNA decoding by a protein? A. Initiation B. Elongation C. Termination D. A and C 22) The signal recognition particle (SRP) is a ribonucleoprotein complex that binds to ribosomes translating polypeptides that bear a signal sequence for targeting to A. the endoplasmic reticulum. B. the nucleus. C. the mitochondria. D. the cytoplasm. 23) What.

16) RNA polymerase is thought to be disengaged from the DNA template by A. the Xrn2 exonuclease B. cleavage and polyadenylation specific-factor (CPSF) C. poly(A) polymerase D. the spliceosome 17) Nuclear pre-mRNA introns are A. self-splicing B. removed by an endoribonuclease C. removed by the spliceosome D. require an external guanosine nucleotide as a cofactor. 18) RNA splicing of nuclear.

1) When making a transgenic mouse by microinjection of foreign DNA into fertilized eggs A. there is random integration of the transgene into the embryonic genome. B. there is disruption or mutation of a targeted gene in the embryonic genome. C. the resulting mice are genetically identical to the donor nucleus. D. the.

51) Based on the DNA fingerprinting (minisatellite analysis with a multilocus probe) results shown in the figure below, is Mr. X or Mr. Y the child’s father? Explain your answer. 52) You separate a mixture of proteins by 2D-PAGE. From one protein spot, you obtain the following peptide sequence by mass.

38) Does the “two hit” hypothesis explain the role of oncogenes and proto-oncogenes in cancer? Why or why not? 54) If you were attempting for the first time to develop a viral gene therapy for a monogenic disease, what factors would you need to consider in your selection of a vector?.

21) The mechanism for nuclear pre-mRNA splicing is similar to the splicing mechanism of A. Group I introns B. Group II introns C. Archael introns D. nuclear tRNA introns 22) It was once assumed that a count of the number of protein-coding genes in an organism would provide a reasonable estimate of the total number.

16) What is a pseudogene? A. A coding sequence that originated by DNA slippage during replication. B. A gene whose sequence is similar to that of functioning genes but does not produce a functioning product. C. A gene with more than two alleles present in a population. D. An open reading frame (ORF).

94) You have developed an in vitro assay for both splicing and polyadenylation. You generate in vitro radioactively labeled pre-mRNA substrates that either include a 5′ cap or lack the 5′ cap. You incubate these labeled pre-mRNA substrates with mammalian cell nuclear extract and run out the products on a.

96) You determine that a single gene encodes a longer protein in embryos and a shorter protein in the adult organism. Describe experiments to determine whether this results from alternative splicing or RNA editing. Provide sample positive results. 97) You have cloned what you thought was the complete sequence of a.

28) Why do you suppose eukaryotes evolved a specialized subnuclear structure for ribosome biogenesis? 29) Eukaryotic ribosomes misincorporate one amino acid for every 1,000-10,000, whereas the eukaryotic replication machinery misincorporates one nucleotide for every ~1x107, a number which goes down to ~1x109 following activity of the mismatch repair machinery. (a) Why.

55) cDNA derived from normal cell mRNA was labeled with a green fluorescent tag (represented as black). cDNA derived from diseased cell mRNA was labeled with a red fluorescent tag (represented as white; the presence of both green and red tags is represented by stripes). The labeled cDNAs were mixed.

23) You have cloned the cDNA for human XPA. You now attempt to use the human XPA cDNA (linked to a promoter) to correct the genetic defect in mice that have the mouse equivalent of the human disease xeroderma pigmentosum, by making transgenic mice. Briefly explain how you would analyze.

16) Which of the following is not a suspected reason for the inefficiency/poor outcomes of reproductive cloning? A. inefficient reprogramming B. premature terminal differentiation in the developing embryo C. telomere length D. chromosome missegregation during early embryonic divisions 17) “Pharming” is A. the growth of transgenic plants as food crops B. the use of Agrobacterium tumefaciens.

1) The majority of the human genome is A. protein-coding gene exons B. intergenic DNA C. genes and gene-related sequences D. interspersed elements 2) What are minisatellites and microsatellites? A. Small, extrachromosomal loops of DNA that are similar to plasmids. B. Parts of viruses that have become integrated into the genome of an organism. C. Incomplete or inactive.

21) The vast majority of human cervical cancers are associated with high-risk human papilloma virus (HPV). HPV is a A. DNA tumor virus B. RNA tumor virus C. retrovirus D. phage 22) Benzo(a)pyrene can induce formation of DNA adducts that interfere with replication and transcription. It acts by a A. promoter insertion mechanism B. enhancer insertion mechanism C..

31) MicroRNAs are processed by the enzymes _______ and ______. One strand of the microRNA is loaded into a silencing complex named _________. The microRNAs target mRNA for ___________ or ___________. A. RISC, Dicer, Drosha, mRNA degradation, translational repression B. Drosha, Dicer, RISC, mRNA degradation, translational repression C. Drosha, Dicer, RISC, alternative splicing,.

16) Recent studies suggest that the expression pattern of a set of human _______ in cancer samples defines that cancer type better than microarray expression data from a set of 16,000 mRNAs. A. snRNAs B. snoRNAs C. miRNAs D. rRNAs 17) The “Philadelphia chromosome” is a reciprocal translocation of chromosome 9 to 22, which causes.

11) The 7-methylguanosine cap structure, the ribose of guanosine is connected to the 5’ end of the mRNA by A. phosphates B. sulfates C. glycerol D. ethylene 12) Which is not a function of the 7-methylguanosine cap? A. protection from exonucleases B. promoting mRNA nuclear export C. stimulation of RNA polymerase elongation D. stimulation of translation 13) The process of.

63) DNA microarray analysis reveals no expression of the pRB tumor suppressor gene in a bone cancer cell line. Would you expect this to be the only difference in expression pattern between normal and bone cancer cells. Why or why not? 64) Analysis of another cell line reveals normal expression levels.

53) What would be the effect on the function of eIF2 of inhibiting its guanine exchange factor? Would the outcome be different if eIF2 were phosphorylated? 54) You are investigating a tRNA whose charging specificity appears to be affected by a U11:G24 to U11:A24 base pair in the D stem. Design an.