Biochemistry Exam 3 Practice Tests 225 Questions with Verified Answers,100% CORRECT

Biochemistry Exam 3 Practice Tests 225 Questions with Verified Answers The complementary strand for the sequence 5' GCACTTCG 3' is - CORRECT ANSWER 5' CGAAGTGC 3' Polysomes...? (a) contain multiple mRNA's (b) contain multiple DNA's (c) contain multiple ribosomes (d) contain multiple RNA polymerases (e) a and c - CORRECT ANSWER (c) contain multiple ribosomes "Multiple ribosomes initiate on a SINGLE mRNA Polyribosomes or polysomes"- Ch 7 Proliferating cell nuclear antigen (PCNA) is commonly used as a diagnostic tool to determine whether cells in a specimen are in S phase. PCNA is a sliding clamp protein. PCNA binds to...? (a) DNA helicase (b) Primase (c) DNA polymerase (d) RNase (e) ligase - CORRECT ANSWER (c) DNA polymerase "Sliding clamp: keeps DNA polymerase attached to template and on lagging strand, releases when Okazaki fragment is completed" -Ch 6 Ubiquitin...? (a) inhibits DNA polymerase (b) inhibits RNA polymerase (c) is added to mRNAs (d) is added to proteins (e) decreases expression of the corresponding mRNA - CORRECT ANSWER (d) is added to proteins "Proteins that need to be degraded are marked by covalent modification - attachment of ubiquitin (a small protein - 76AA)" -Ch 7 Which of the following does NOT occur before a eukaryotic mRNA is exported from the nucleus? (a) The ribosome binds to the mRNA. (b) The mRNA is polyadenylated at its 3' end. (c) 7-methyl-G is added in a 5' to 5' linkage to the mRNA. (d) RNA polymerase dissociates. (e) Splicing out of introns in mRNA. - CORRECT ANSWER a) The ribosome binds to the mRNA. Which amino acid would you expect a tRNA with the anticodon 5'-CCA-3' to carry? [Use the genetic code provided in question 16 to answer this question]. (a) proline (b) glycine (c) serine (d) threonine (e) tryptophan - CORRECT ANSWER (e) tryptophan if the tRNA has the anticodon 5'-CCA-3', the mRNA would have the codon 5'-UGG-3' UGG codes for Trp or tryptophan Transcription initiation in eukaryotes requires the coordinated action of many proteins. Which protein is responsible for recruitment of splicing factors to the CTD of RNA Polymerase? (a) snRNP (b) TFIID (c) TBP (d) TFIIH (e) TFIIA - CORRECT ANSWER d) TFIIH miRNA's and siRNA's...? (a) inhibit DNA polymerase (b) inhibit RNA polymerase (c) increase expression of the corresponding mRNA (d) regulate the final step in RNA splicing (e) decrease expression of the corresponding mRNA - CORRECT ANSWER (e) decrease expression of corresponding mRNA. siRNA binds with mRNA and RNA inference is activated and thus mRNA is cleaved. miRNA are involved in transcriptional and post transcriptional regulation of gene expression.. Mutations of the zinc finger protein WT1 cause Wilms' tumor, a pediatric renal tumor. Zinc fingers are typically found in...? (a) methylases and acetylases (b) just acetylases (c) telomerases (d) ribozymes (e) transcription factors - CORRECT ANSWER (e) transcription factors Circle all that applies. Okazaki fragments are...? (a) synthesized by the RNA polymerase (b) composed of RNA and DNA (c) specific to eukaryotes (d) complementary to the leading template strand (e) synthesized from 5' to 3' (f) are about 200 bp long - CORRECT ANSWER (d) complementary to the leading template strand (e) synthesized from 5' to 3' (f) are about 200 bp long 12. Prepare a 5-liter solution of a 10 mM JGP, 10 mM NaCl solution using dry JGP powder (100 g/mol), a 1 M NaCl stock solution and water. JGP: __________ NaCl: ________ Water: _______ - CORRECT ANSWER KNOW HOW TO SOLVE THIS TYPE OF PROBLEM What are the basic steps involved in ribosome assembly on a eukaryotic mRNA? - CORRECT ANSWER UNSURE The two ribosomal subunits come together on an mRNA molecule near its 5' end: -Small subunit matches tRNAs with codons -Large subunit catalyzes formation of peptide bonds Three binding sites: -A site (aminoacyl-tRNA): charged tRNA binds to its codon -P site (peptidyl-tRNA): condensation of amino acids -E site (exit): where the "uncharged" tRNA is ejected You are a nurse in charge of controlling the spread of infectious diseases in a hospital. About 4 weeks ago there was an outbreak of vancomycin-resistant Enterococcus faecium in a surgical oncology ward. This morning you get a report of 4 children in a pediatric ward developing vancomycin-resistant Staphylococcus aureus infections. One of the pediatricians tells you that the pediatricians (none of whom took BIOL 213) have never before seen vancomycinresistant Staphylococcus aureus infections, and they have no idea how this could have happened. Explain what happened, drawing diagrams. - CORRECT ANSWER What is the role of telomerase in the cell? How would deletion of the telomerase gene affect rapidly dividing cells? - CORRECT ANSWER telomerase is a ribonucleoprotein complex that replicate chromosome ends in DNA synthesis (Ch 6) deletion of telomerase leads to telomeres to becoming abnormally short as cells divide. The shortened telomeres likely trigger cells that divide rapidly, such as cells that line the inside of the lungs, to stop dividing or to die prematurely What is a nucleosome (i.e., what are the constituents)? - CORRECT ANSWER 146 bp DNA fragment + 2 H2A, 2 H2B, 2 H3 and 2 H4 (histone octamer) linker DNA connects to DNA wrapped around histones ("beads-on-string") H1 (required for 30 nm fiber packing level) H2A, H2B, H3 and H4 (nucleosome core) look at slide 36? Bacteria don't have nucleosomes Provide two distinct examples that illustrate how nucleosomes regulate molecular functions in the cell. - CORRECT ANSWER Small DNA fragments of ~200bp are synthesized Enzyme? - CORRECT ANSWER DNA polymerase "Extension of the RNA primer by DNA polymerase generates the Okazaki fragment (~200 nt)" The DNA helix is further unzipped enzyme? - CORRECT ANSWER DNA Helicase? ("further?") A short RNA fragment is synthesized to serve as a primer for the replication of the lagging strand template enzyme? - CORRECT ANSWER DNA primase RNA is replaced with DNA enzyme? - CORRECT ANSWER Repair polymerase A short RNA fragment is synthesized to serve as a primer for the replication of the leading strand template enzyme? - CORRECT ANSWER DNA primase Double Strand DNA is denatured at the origin of replication enzyme? - CORRECT ANSWER initiator proteins DNA fragments are joined together enzyme? - CORRECT ANSWER ligase The leading strand is synthesized enzyme? - CORRECT ANSWER primase? RNA fragments are degraded enzyme? - CORRECT ANSWER Ribonuclease Ribonucleoprotein complexes are roughly half RNA and half protein. Provide three key enzymes in eukaryotic molecular biology that are part RNA, part protein? - CORRECT ANSWER Spliceosome (Ch 7) ribosomes (Ch 7) telomerase (Ch 6) Imagine the two situations shown in the figure below. 1.) In cell I, a transient signal induces the synthesis of protein A, which is a transcriptional activator that turns on many genes including its own. 2.) In cell II, a transient signal induces the synthesis of protein R, which is a transcriptional repressor that turns off many genes including its own. In which, if either, of these situations will the descendants of the original cell "remember" that the progenitor cell had experienced the transient signal? Explain your reasoning. - CORRECT ANSWER In cell I the gene is being activated leading to the synthesis of proteins that turn on many other genes including it. So there will be extensive functioning of the cell and assuming that the gene for cellular memory is activated, we can infer that the next generation cells will remember the kind of functioning in the parent cells. In cell II the mRNA is producing repressor proteins that stops transcription of the genes. So there will be no scope to pass on this information to the next generation cells. So in the case of cell I the descendants will remember that the original cell had experienced transient signal. Which of the following types of mutations would be predicted to harm an organism? Explain your answers. (a) Insertion of a single nucleotide near the end of a coding sequence. (b) Removal of a single nucleotide near the beginning of the coding sequence. (c) Deletion of three consecutive nucleotides in the middle of the coding sequence. (d) Deletion of four consecutive nucleotides in the middle of the coding sequence. (e) Substitution of one nucleotide for another in the middle of the coding sequence. - CORRECT ANSWER a- Not very harmful. This might change the structure of the protein, but otherwise, nothing to worry about. b- This is called a frameshift mutation and this is the most harmful. This will completely change the reading frame and will cause a dysfunctional or toxic protein to be made. c- This is not very harmful. It will result in the deletion of a single amino acid from a polypeptide chain. d- This is harmful, but not as harmful as B. This will cause the reading frame to change and can lead to a truncated protein. e-Not very harmful and does exactly as explained. B and D are harmful, B is the most harmful Which amino acid would you expect a tRNA with the anticodon 5'-AGC-3' to carry? [Use the genetic code provided at the beginning of this exam to answer this question]. (a) arginine (Arg) (b) alanine (Ala) (c) serine (Ser) (d) threonine (Thr) (e) none of the above answers are correct - CORRECT ANSWER (b) alanine (Ala) if the tRNA has the anticodon 5'-AGC-3', the mRNA would have the codon 5'-GCU-3' GCU codes for Ala or alanine The complementary strand for the sequence 5' GATCGGTACC 3' is - CORRECT ANSWER 5' GGTACCGATC 3' The lagging strand is synthesized discontinuously at the replication fork because...? (a) the lagging strand template is discontinuous. (b) DNA polymerase always falls off the template DNA every ten nucleotides or so. (c) DNA polymerase can polymerize nucleotides only in the 5′-to-3′ direction. (d) DNA polymerase removes the last few nucleotides synthesized whenever it stops. (e) None of the above - CORRECT ANSWER c) DNA polymerase can polymerize nucleotides only in the 5′-to-3′ direction. The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. Once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins does not form part of the octameric core? (a) H1 (b) H2A (c) H2B (d) H3 (e) H4 - CORRECT ANSWER (a) H1 (slide33, Ch 5) What histone proteins form the octameric core? - CORRECT ANSWER H2A, H2B, H3, H4 You are examining the DNA sequences that code for the enzyme phosphofructokinase in skinks and Komodo dragons. You notice that the coding sequence that actually directs the sequence of amino acids in the enzyme is very similar in the two organisms but that the surrounding sequences vary quite a bit. What is the most likely explanation for this? (a) Coding sequences are repaired more efficiently. (b) Coding sequences are replicated more accurately. (c) Coding sequences are packaged more tightly in the chromosomes to protect them from DNA damage. (d) Mutations in coding sequences are more likely to be deleterious to the organism than mutations in noncoding sequences. (e) Recombination between skink and Komodo dragon DNA occurred recently - CORRECT ANSWER (d) Mutations in coding sequences are more likely to be deleterious to the organism than mutations in noncoding sequences. What occurs before eukaryotic mRNA is exported from the nucleus? - CORRECT ANSWER - The mRNA is polyadenylated at its 3' end. - 7-methyl-G is added in a 5' to 5' linkage to the mRNA. - RNA polymerase dissociates. - Splicing out of introns in mRNA. In a DNA double helix, _____________________. (a) the two DNA strands are identical (b) purines pair with purines (c) thymine pairs with cytosine (d) the two DNA strands run antiparallel (e) uracil pairs with adenine - CORRECT ANSWER (d) the two DNA strands run antiparallel Transcription is similar to DNA replication in that...? (a) it requires a molecule of DNA helicase to unwind the DNA. (b) it uses the same enzyme as that used to synthesize RNA primers during DNA replication. (c) the newly synthesized RNA remains paired to the template DNA. (d) nucleotide polymerization occurs only in the 5′-to-3′ direction. (e) an RNA transcript is synthesized discontinuously and the pieces then joined together. - CORRECT ANSWER (d) nucleotide polymerization occurs only in the 5′-to-3′ direction. i think Leucine zipper are typically found in: (a) methylases and acetylases (b) just acetylases (c) telomerases (d) ribozymes (e) transcription factors - CORRECT ANSWER (e) transcription factors i think Enhancers...? (a) are only found upstream of genes. (b) can be found upstream or downstream of genes. (c) need to be immediately adjacent to the AUG. (d) need to be immediately adjacent to the transcription start site. (e) need to be immediately adjacent to the kinetochore. - CORRECT ANSWER A? Usually located upstream of initiation site AKA regulatory DNA sequences (Ch8) Genetic changes that allow new organisms to evolve...? (a) arise only from gene duplication. (b) arise only from point mutations. (c) arise only from the insertion of transposons. (d) arise from gene duplications, transposons, and point mutations. (e) arise only from gene duplications and point mutations. - CORRECT ANSWER (d) arise from gene duplications, transposons, and point mutations What is an example of a sequence that can fully base-pair with itself? - CORRECT ANSWER 5'-GGATATCC-3' complimentary strand: 5'-GGATATCC-3' predict when lac operon is off on/off - CORRECT ANSWER only on when there is no glucose and lactose is present Is the lac operon on or off? in the presence of glucose and lactose - CORRECT ANSWER OFF Is the lac operon on or off? in the presence of glucose and the absence of lactose - CORRECT ANSWER OFF Is the lac operon on or off? in the absence of glucose and the absence of lactose - CORRECT ANSWER OFF Is the lac operon on or off? in the absence of glucose and the presence of lactose - CORRECT ANSWER ON Blocking replication is a potential way to stop the proliferation of tumor cells. What are four key enzymes involved in replication, and what do they do? - CORRECT ANSWER 1A. DNA polymerase-synthesizes DNA 5'-->3', needs primer to use as a template 1B. repair polymerase- replaces DNA with RNA (type of DNA polymerase) 2. DNA primase- synthesizes short RNA stands that act as primers 3. ribonuclease- degrades RNA primers 4.DNA ligase- joins fragments 5'-->3' Explain in about 3-4 sentences what is the role and function of ubiquitin? - CORRECT ANSWER Degrade proteins whose lifespan needs to be short Proteins are degraded to amino acids by proteases This process is called proteolysis Proteins that need to be degraded are marked by covalent modification - attachment of ubiquitin (a small protein - 76AA) Formation of a chain of ubiquitin Why is there no tRNA with a 5'- CUA -3' anticodon? - CORRECT ANSWER mRNA codon is 5'-UAG-3' this is a STOP codon "There are no tRNA for stop codons"- Ch 7 The biotech company Geron is currently testing a telomerase inhibitor (Imetelstat) in Phase II clinical trials as a therapeutic for lung cancer. How would a telomerase inhibitor block tumors? - CORRECT ANSWER Telomerase is needed to replicate chromosome ends Due to telomerase inhibition, activity, or expression, these drugs might kill tumor cells by allowing telomeres to shrink or by provoking apoptosis Indicate below how to prepare 3 liters of a 10 mM TATN, solution at pH 11.0 using TATN powder (MW = 10 g/mole), a 0.1 M NaOH (strong base) stock solution and water. Be sure to clearly indicate units. TATN: _________________ 0.1 M NaOH stock: _________________ Water: __________________ - CORRECT ANSWER label replication bubble - CORRECT ANSWER Patients with Lynch syndrome have an extremely high incidence of intestinal and colon cancer, as well as stomach, urinary tract, brain, dermal, and other cancers. The syndrome is due to a dominant genetic disorder, and roughly half of the children of a patient with Lynch syndrome will inherit the disorder. The tumors are due to impaired DNA mismatch repair. You are a physician treating the colon cancer in a patient with Lynch syndrome, and the patient asks you to explain what DNA mismatch repair is. Drawing diagrams, please explain DNA mismatch repair. - CORRECT ANSWER DNA mismatch repair proteins recognize the newly synthesized strand and selectively excise and resynthesize this strand 1. DNA mismatch repair protein attaches at the DNA mismatch and a "nick" 2. removes newly synthesized DNA from this region 3. repair polymerase synthesizes and replaces this DNA 4. DNA ligase reconnects the strands The complementary strand for the sequence 5' GATCCGTATC 3' is...? - CORRECT ANSWER 5' GATACGGATC 3' Which of the following statements about eukaryotic RNA polymerase is FALSE? (a) RNA polymerase can start polymerizing on a single-stranded DNA template (b) There are three types of RNA polymerase in eukaryotes (c) RNA polymerase generates more errors than DNA polymerase (d) mRNA are mostly transcribed by RNA polymerase I (e) tRNA are mostly transcribed by RNA polymerase III - CORRECT ANSWER d) mRNA are mostly transcribed by RNA polymerase I What is true about eukaryotic RNA polymerase? - CORRECT ANSWER -RNA polymerase can start polymerizing on a single-stranded DNA template -There are three types of RNA polymerase in eukaryotes -tRNA are mostly transcribed by RNA polymerase III -mRNA are mostly transcribed by RNA polymerase II -RNA polymerase error rate is 1 in 10^4 -DNA poly. error rate is 1 in 10^7 base pairs RNA ces more errors than DNA poly Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon? (a) Eukaryotes have three types of RNA polymerase. (b) Eukaryotic RNA polymerases require general transcription factors. (c) The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter. (d) Prokaryotic genes are packaged into nucleosomes. (e) Eukaryotic genes are monocistronic - CORRECT ANSWER (c) The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter. You have a segment of DNA that contains the following sequence: 5′-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3′ 3′-CCT GATCTG T T ATCCCT GGATCTC TAAGGCTTT-5′ You know that the RNA transcribed from this segment contains the following sequence: 5′-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3′ Which of the following choices best describes how transcription occurs? (a) the top strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′ (b) the top strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′ (c) the bottom strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′ (d) the bottom strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′ (e) none of the above - CORRECT ANSWER (c) the bottom strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′ Your friend works in a lab that is studying why a particular mutant strain of Drosophila grows an eye on its wing. Your friend discovers that this mutant strain of Drosophila is expressing a transcription factor incorrectly (named Pax6). In the mutant Drosophila, this transcription factor, which is normally expressed in the primordial eye tissue, is now misexpressed in the primordial wing tissue, thus turning on transcription of the set of genes required to produce an eye in the wing primordial tissue. If this hypothesis is true, which of the following types of genetic change would most likely lead to this situation? (a) a mutation within the transcription factor gene that leads to a premature stop codon after the third amino acid (b) a mutation within the transcription factor gene that leads to a substitution of a positively charged amino acid for a negatively charged amino acid (c) a mutation within an upstrea - CORRECT ANSWER (c) a mutation within an upstream enhancer of the gene Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the adenosine in the sequence TCAT is depurinated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication? (a) TCGT (b) TAT (c) TCT (d) TGTT (e) None of the above - CORRECT ANSWER (c) TCT Several members of the same family were diagnosed with the same kind of cancer when they were unusually young. Which one of the following is the most likely explanation for this phenomenon? It is possible that the individuals with the cancer have _______________________. (a) inherited a cancer-causing gene that suffered a mutation in an ancestor's somatic cells. (b) inherited a mutation in a gene required for DNA synthesis. (c) inherited a mutation in a gene required for mismatch repair. (d) inherited a mutation in a gene required for the synthesis of purine nucleotides. (e) inherited a mutation that inhibits the telomerase activity - CORRECT ANSWER (c) inherited a mutation in a gene required for mismatch repair. Which of the following statements is false? (a) A mutation that arises in a mother's somatic cell often causes a disease in her daughter. (b) All mutations in an asexually reproducing single-celled organism are passed on to progeny. (c) In an evolutionary sense, somatic cells exist only to help propagate germ-line cells. (d) A mutation is passed on to offspring only if it is present in the germ line. (e) The pool of germ line cells become distinct from somatic cells early in the development. - CORRECT ANSWER (a) A mutation that arises in a mother's somatic cell often causes a disease in her daughter. germ cells would do this What part of the DNA replication process would be most directly affected if a strain of bacteria lacking DNA primase were used to make the cell extracts? (a) initiation of DNA synthesis (b) ligation of the okazaki fragments (c) Okazaki fragment synthesis (d) leading-strand elongation (e) lagging-strand completion - CORRECT ANSWER (a) initiation of DNA synthesis Which of the following statements is FALSE: (a) The proteasome has the shape of a cylinder. (b) Proteins that are covalently linked to ubiquitin are targeted to the proteasome to be degraded. (c) The lifespan of proteins can vary greatly (from seconds to years) (d) Misfoldfed or damaged proteins are degraded by the proteasome (e) The proteasome is a ribonucleoprotein complex - CORRECT ANSWER (e) The proteasome is a ribonucleoprotein complex Your colleague has isolated a new species of bacteria and sequenced its genome. Given that this bacteria genome contain 30% of Adenosine, what is the proportion of: Cytosine: _____________ Guanosine: _____________ Thymidine: _____________ - CORRECT ANSWER adenosine: 30% Cytosine: 20% Guanosine: 20% Thymidine: 30% The two strands of a DNA double helix can be separated by heating. If you raised the temperature of a solution containing the following three DNA molecules, in what order do you suppose they would "melt" (i.e., the two strand would dissociate)? Explain your answer. A. 5'-GCACGTGGCCGATGTCGGTGCAGTGCAGG-3' 3'-CGTGCACCGGCTACAGCCACGTCACGTCC-5' B. 5'-TATTCTAGTTACTAATATTAGCTAATTATAT-3' 3'-ATAAGATCAATGATTATAATCGATTAATATA-5' C. 5'-TGCGATCGATCGTGAATC-3' 3'-ACGCTAGCTAGCACTTAG-5' - CORRECT ANSWER C, B, A The melting temperature depends on both the size of the strand and the number of H-bonds (the more of them the higher the melting temperature) The error rate of the DNA polymerase is exceptionally low (~1 error every 109 bp). Please describe in ~5 sentences two mechanisms that are used by the DNA polymerase during replication to achieve this extremely low rate of errors. - CORRECT ANSWER Okazaki fragment - CORRECT ANSWER short segment of DNA synthesized discontinuously in small segments in the 3' to 5' direction by DNA polymerase RNA primer - CORRECT ANSWER Sequence of RNA nucleotides bound to a region of single-stranded DNA to initiate DNA replication. leading vs lagging strand - CORRECT ANSWER Leading: elongate continuously into the widening replication fork Lagging: replicates away from the fork, must wait until it widens to polymerize and is discontinuous, leading to Okazaki fragments The Lacheinmal protein is a hypothetical protein that causes people to smile more often. It is inactive in many chronically unhappy people. The mRNA isolated from a number of different unhappy individuals in the same family was found to lack an internal stretch of 173 nucleotides that is present in the Lacheinmal mRNA isolated from happy members of the same family. The DNA sequences of the Lacheinmal genes from the happy and unhappy family members were determined and compared. They differed by a single nucleotide substitution, which lay in an intron. What can you say about the molecular basis of unhappiness in this family? Elaborate your answer in about 3-5 sentences. (Hints: [1] Can you hypothesize a molecular mechanism by which a single nucleotide substitution in a gene could cause the observed deletion in the mRNA? Note that the deletion is internal to the mRNA. [2] Assuming that the 173-base pair deletion rem - CORRECT ANSWER a single nucleotide substitution may change the Intron-Exon boundary which play vital role in the splicing mechanism. it alters the splicing mechanism, substitution may change sequence present at splice site so that splicing machinery could not recognise the spilce site it moves to next exon-intron boundary site (exon skipping). in such a way the mutant mRNA lost the 173 base pair that are present in the functional lacheinmal mRNA. 2) 173 base pair deletion in the coding sequence of lacheinmal mRNA leads to Protein difference between happy and unhappy people, because the deletion occurs at coding region upto the missing region the aminoacid sequence is same in happy and unhappy people there after due to the deletion of 173 bases it shift the reading frame of mRNA and totally different aminoacid sequence will observe in the happy and unhappy people. Indicate below how to prepare 6 liters of a 10 mM TATN, solution at pH 11.0 using TATN powder (MW = 10 g/mole), a 0.1 M NaOH (strong base) stock solution and water. Be sure to clearly indicate units. TATN: _________________ 0.1 M NaOH stock: _________________ Water: __________________ - CORRECT ANSWER Which of the following statements are correct? Explain your answers. A. In bacteria, but not in eukaryotes, many mRNA contain the coding region for more than one gene. B. Most DNA-binding proteins bind to the major grove of the DNA double helix. C. Of the major points in gene expression (transcription, RNA processing, RNA transport, translation and control of protein's activity), transcription initiation is one of the most common. - CORRECT ANSWER Bacterial cells can take up the amino acid tryptophan (Trp) from their surroundings. However, if there is an insufficient external supply, they can synthesize tryptophan from other small molecules. The Trp repressor is a transcriptional regulator that shuts off the transcription of genes that code for the enzymes required for the synthesis of tryptophan. What would happen to the regulation of the tryptophan operon in cells that express a mutant form of the tryptophan repressor that: (i) cannot bind DNA? (ii) cannot bind tryptophan? (iii) binds to DNA even in the absence of tryptophan? Elaborate your answers for each of the three possibilities in a few sentences. You can draw some schematics if that helps. - CORRECT ANSWER (i)- Usually when tryptophan is present, the repressor is active and operon gets off. But in the absence of tryptophan, repressor is inactive and opeon is on. If the mutant form of tryptophan repressor can not bind to DNA, the operon keeps off producing tryptophan even in its presence. Overproduction and high level of tryptophan can not be regulated as the mutant repressor is not in working mode. (ii)-Usually tryptophan acts as a corepressor binding with the repressor. This binding makes the repressor active. If the mutant repressor can not bind with the tryptophan, the active form of the repressor can not be formed and the tryptophan production is continued. (iii)-If the mutant repressor binds to DNA even in the absence of tryptophan, it prevents the production of tryptophan. This leads to total lack of tryptophan. But in this case, tryptophan is needed first to activate the repressor. And if the mutant repressor is able to bind the DNA, even in the absence of tryptophan, this can lead to keep the operon off always, keeping the downstream DNA away from transcription of necessary enzymes for the production of tryptophan. Which of the following can be translated into protein? (a) rRNA (b) tRNA (c) mRNA (d) miRNA (e) C and D - CORRECT ANSWER (c) mRNA All of the following is true about eukaryotic transcription except? (a) RNA polymerase is a processive enzyme (b) RNA made is complementary to DNA according to Chargaff's Rules (c) Three different types of RNA polymerases can be used (d) A sigma factor allows RNA polymerase to recognize the promoter (e) The initial transcript must be processed before it leaves the nucleus - CORRECT ANSWER d) A sigma factor allows RNA polymerase to recognize the promoter What is true about eukaryotic transcription? - CORRECT ANSWER (a) RNA polymerase is a processive enzyme (b) RNA made is complementary to DNA according to Chargaff's Rules (c) Three different types of RNA polymerases can be used (e) The initial transcript must be processed before it leaves the nucleus In eukaryotes, tRNA are transcribed by: (a) RNA Polymerase I (b) RNA Polymerase II (c) RNA Polymerase III (d) All of the above (e) None of the above - CORRECT ANSWER (c) RNA Polymerase III All of the following would inhibit DNA replication except: (a) Helicase that is in the cytosol (b) Primase cannot put down primer (c) Chromosomes do not condense (d) DNA Polymerase malfunctions (e) Promoter regions are not recognized - CORRECT ANSWER What inhibits DNA replication? - CORRECT ANSWER The complementary strand for the sequence 5' TAGCCGTATC 3' is? - CORRECT ANSWER 5' GATACGGCTA 3' Transcription factors regulate (a) DNA polymerase activity (b) RNA polymerase binding to DNA (c) RNA polymerase binding to RNA (d) RNA splicing (e) RNA binding to ribosomes - CORRECT ANSWER b) RNA polymerase binding to DNA Indicate below how to prepare 3 liters of a 10 mM JPG, solution at pH 12.0 using JPG powder (MW = 10 g/mole), a 1 M NaOH (strong base) stock solution and water. Be sure to clearly indicate units. JPG: _________________ 1 M NaOH stock: _________________ Water: __________________ - CORRECT ANSWER Twenty-seven percent of a cell's DNA contains adenine bases. What is the amount of guanine present in the cell's DNA? - CORRECT ANSWER adenine: 27% therefore thymine = 27% remaining 46% guanine and cytosine each make up 23% What would happen if the following structure was incorporated into a growing piece of DNA. Explain your answer. ATP without adenine ribose with a base, 3 phosphates - CORRECT ANSWER A transposon jumped into a region of DNA which eventually causes the cell to die. What kind of region do you think the transposon moved to? Explain your reasoning - CORRECT ANSWER Explain in a few sentences why only mutations in germ-cell lines contribute to evolution. - CORRECT ANSWER Explain in a few sentences why neutral (silent) mutations in the exons of protein coding genes are usually observed on the third nucleotide of a codon. - CORRECT ANSWER The enzyme Phosphofructokinase is the rate-limiting enzyme of glycolysis, and catalyze the reaction: Fructose 6-phosphate -->Fructose 1,6-biphosphate The protein is made of 780 amino acids. The codon 146, of the sequence UCA and which encodes for a serine, can be mutated in the human population. These different mutations are all point mutations, and lead to either of these codons: (i) ACA (ii) UAA (iii) CCA (iv) UCC Surprisingly, the output of these 4 different mutations on human health is highly dependent on the type of mutation, and ranges from no defects to lethality at the embryonic stage. Using your knowledge, the genetic code, and what we have seen in class, please explain why - CORRECT ANSWER Is this statement true or false? Explain your answer. "Since introns do not contain protein coding information, they do not have to be removed precisely (meaning, a nucleotide here and there should not matter) from the primary transcript during RNA splicing." - CORRECT ANSWER False (imprecise removal could cause a frame shift mutation.) You are examining the DNA sequences that code for the enzyme aldolase in mice and rats. You notice that the coding sequence that actually directs the sequence of amino acids in the enzyme is very similar in the two organisms but that the surrounding sequences vary quite a bit. What is the most likely explanation for this? (a) Recombination between the mouse and rat DNA occurred recently. (b) Coding sequences are repaired more efficiently. (c) Coding sequences are packaged more tightly in the chromosomes to protect them from DNA damage. (d) Mutations in coding sequences are more likely to be deleterious to the organism than mutations in noncoding sequences. (e) Coding sequences are replicated more accurately - CORRECT ANSWER You have a segment of DNA that contains the following sequence: 5'-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3' 3'-CC TGATCT GTT AT CCCTGGAT CT CTAAGGCTTT-5' If you know that the RNA transcribed from this segment contains the following sequence: 5'-UUUGCCAAUGUGUAGGUCCCUAUUCUGUAGUCC-3' Which of the following choices best describes how transcription occurs? (a) The top strand is the template strand; RNA pol. moves along this strand from 5' to 3'. (b) The top strand is the template strand; RNA pol. moves along this strand from 3' to 5'. (c) The bottom strand is the template strand; RNA pol. moves along this strand from 5' to 3'. (d) The bottom strand is the template strand; RNA pol. moves along this strand from 3' to 5'. (e) None of the above. - CORRECT ANSWER In eukaryotes, the rRNA (18S and 28S rRNA) are transcribed by: (a) RNA Polymerase I (b) RNA Polymerase II (c) RNA Polymerase III (d) All of the above (e) None of the above - CORRECT ANSWER (a) RNA Polymerase I The figure below shows the evolutionary history of the globin gene family members... - CORRECT ANSWER KNOW HOW TO SOLVE The complementary strand for the sequence 5' TAGCCGTATC 3' is - CORRECT ANSWER 5' GATACGGCTA 3' All of the following is true about prokaryotic transcription except: (a) RNA polymerase is a processive enzyme (b) Three different types of RNA polymerases can be used (c) RNA made is complementary to DNA according to Chargaff's Rules (d) A sigma factor allows RNA polymerase to recognize the promoter (e) The RNA is transcribed from 5' to 3'. - CORRECT ANSWER What is true about prokaryotic transcription? - CORRECT ANSWER Given the size of the human diploid genome (6.4´109 base pairs) and the repair mechanisms that are in play during DNA replication, a daughter cell differs to the mother cell by about: (a) 0 nucleotide. (b) 6 nucleotides. (c) 60 nucleotides (d) 600 nucleotides (e) 6000 nucleotides. - CORRECT ANSWER Which of the following statement about telomerases is wrong: (a) telomerases are ribonucleoprotein complexes. (b) telomerase expression is usually lower in cancer cells. (c) telomerases are needed to replicate chromosome ends. (d) telomerases synthetize DNA from 5' to 3' using an RNA template. (e) None of the above. - CORRECT ANSWER (b) telomerase expression is usually lower in cancer cells. (I THINK) What is true about telomerase? - CORRECT ANSWER (a) telomerases are ribonucleoprotein complexes (c) telomerases are needed to replicate chromosome ends. (d) telomerases synthetize DNA from 5' to 3' using an RNA template. Which of the following statement about horizontal gene transfer is wrong: (a) Horizontal gene transfer is frequent in prokaryotes and eukaryotes. (b) Horizontal gene transfer is a major problem for microbes' antibiotic resistance. (c) Horizontal gene transfer allows the transfer of plasmids or even whole chromosomes from one cell to another cell. (d) During horizontal gene transfer, the donor cell and recipient cell communicate through a sex pilus and a bridge. (e) None of the above. - CORRECT ANSWER What is true about horizontal gene transfer? - CORRECT ANSWER Indicate below how to prepare 5 liters of a 20 mM JPG, solution at pH 11.0 using JPG powder (MW = 20 g/mole), a 0.1 M NaOH (strong base) stock solution and water. Be sure to clearly indicate units. JPG: _________________ 0.1 M NaOH stock: _________________ Water: __________________ - CORRECT ANSWER The gene BRCA1 codes for a large protein of 1863 amino acids that is involved in both homologous and non-homologous DNA recombination. Mutations in BRCA1 are found in several types of cancer, and more particularly in breast cancer. As such, genetic testing for mutation(s) in BRCA1 is encouraged for women who are at risk of developing breast cancer based on family history. (a) Explain in a few sentences which type of DNA damage is more specifically repaired by homologous and non-homologous DNA recombination, and why mutations in BRCA1 are therefore more likely to contribute to increased risks of cancer. - CORRECT ANSWER A genetic counselor is asked to analyze mutations of 5 patients who underwent genetic testing, and has then to tell them whether they have an increased risk of developing cancer. Below is a description on how mutations in the BRCA1 gene will affect the coding sequence of BRCA1 (i.e., how it will affect the codons) : Patient 1: The codon 774, of the sequence CAU, has been depurinated. Patient 2: The codon 543, of the sequence GCU, is mutated to GGU Patient 3: The codon 347, of the sequence CUG, is mutated to UUG Patient 4: The codon 122, of the sequence AAG, is mutated to UAG Patient 5: The codon 691, of the sequence UGC, is mutated to AGU Determine how each of the 5 mutations are likely to affect BRCA1 function, and describe what do you think the genetic counselor will tell to each of her 5 patients. Your answer must incorporate a "ranking" between which patient(s) are the most at risk at developing cancer, and t - CORRECT ANSWER evolutionary relationships between gene sequences - CORRECT ANSWER Starting from DNA and up to an active protein, gene expression can be regulated at many steps. Using the figure below, provide 5 different major steps at which this regulation can occur. - CORRECT ANSWER Provide below the name of 5 enzymes that are used during DNA replication, and briefly describe their role. - CORRECT ANSWER start codon - CORRECT ANSWER AUG (methionine) stop codons - CORRECT ANSWER UAA, UAG, UGA Initiator proteins - CORRECT ANSWER helix opening at replication origin DNA Polymerase - CORRECT ANSWER polymerization (5ʼ-3ʼ) proofreading (3ʼ-5ʼ) DNA Primase - CORRECT ANSWER synthesis of short RNA primer Ribonuclease - CORRECT ANSWER degradation of RNA primer Repair polymerase - CORRECT ANSWER replace RNA with DNA DNA ligase - CORRECT ANSWER joining of DNA fragments DNA Helicase - CORRECT ANSWER unzipping DNA helix prior to replication Single-stranded DNA-binding protein - CORRECT ANSWER prevent reanealing Sliding clamp - CORRECT ANSWER keeps DNA polymerase attached to template and on lagging strand, releases when Okazaki fragment is completed coding strand - CORRECT ANSWER sense strand not used as a template during transcription since it is complementary to the template strand it is *identical* to the mRNA but thymine nucleotides in this strand have been replaced with uracil template strand - CORRECT ANSWER the antisense strand of DNA that acts as template during transcription so that the complementary RNA strand formed carries the same code for a protein as the DNA sense strand. mRNA - CORRECT ANSWER codes for proteins rRNA - CORRECT ANSWER form the core of the ribosome and catalyze protein synthesis miRNA - CORRECT ANSWER regulate gene expression tRNA - CORRECT ANSWER serve as adaptors between mRNA and amino acids during protein synthesis Euk. RNA pol I: - CORRECT ANSWER most rRNA genes Euk. RNA pol II: - CORRECT ANSWER protein-encoding genes (makes mRNA) Euk. RNA pol III: - CORRECT ANSWER tRNA, 5S rRNA, small structural RNA genes what is true about proteasomes - CORRECT ANSWER a) The proteasome has the shape of a cylinder. b) Proteins that are covalently linked to ubiquitin are targeted to the proteasome to be degraded. c) The lifespan of proteins can vary greatly (from seconds to years) (d) Misfoldfed or damaged proteins are degraded by the proteasome What part of the DNA replication process would be most directly affected if a strain of bacteria lacking helicase were used to make the cell extracts? a. initiation of DNA synthesis b. Okazaki fragment synthesis c. leading - strand elongation d. lagging - strang completion - CORRECT ANSWER a. initiation of DNA synthesis DNA primase is required for initiation of replication process hence lacking DNA primase enzyme affects initiation of DNA replication. What part of the DNA replication process would be most directly affected if a strain of bacteria lacking single - strand binding protein were used to make the cell extracts? a. initiation of DNA synthesis b. Okazaki fragment synthesis c. leading - strand elongation d. lagging - strand completion - CORRECT ANSWER c. leading - strand elongation After the primase is bound to complentary sequence, the single strand binding proteins (SSB proteins) are associated with primase complex to start the replication process. If SSB proteins are lacking, then strand elongation process is affected. What part of the DNA replication process would be most directly affected if a strain of bacteria lacking DNA ligase were used to make the cell extracts? a. initiation of DNA synthesis b. Okazaki fragment synthesis c. leading - strang elongation d. lagging - strand completion - CORRECT ANSWER d. lagging - strand completion DNA ligase is the enzyme that joins the DNa fragments (okazaki fragments of lagging strand) to complete the strand. If DNA ligase is lacking, then lagging strand completion is affected. Sometimes chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the cytosine in the sequence TCAT is deaminated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication? - CORRECT ANSWER TTAT 1. Which statement about RNA polymerase is false? a.RNA polymerase is an enzyme b.Rna polymerase synthesizes new mRNA in the 3' to 5' direction adding new nucleotides to the 5' end of the growing polynucleotide chain c.RNA polymerase has helicase activity d.RNA polymerase adds either an A, U, C, or G ribonucleotide to a growing RNA strand based on the complementary base that is present on DNA - CORRECT ANSWER b.Rna polymerase synthesizes new mRNA in the 3' to 5' direction adding new nucleotides to the 5' end of the growing polynucleotide chain 2. You hypothesize that the virus X binding to cells initiates a specific cell signal transduction pathway for which you know some of the key protein kinases involved. How could you directly test the hypothesis that virus binding activates these kinases? a. Infect cells and examine DNA replication kinetics b. Infect cells and measure ion channel activity Infect cells and compare DNA replication in infected cells versus non-infected cells c. Compare the amount of phosphorylated protein kinases in infected cells versus non-infected cells d. Measure the activity of the lac operon in infected cells versus non-infected cells. - CORRECT ANSWER d. Measure the activity of the lac operon in infected cells versus non-infected cells. 3. Starting with the following stretch of tRNAs, write down the mRNA that is recognized by the tRNAs tRNA= 3' AAG UUU GGG AUA 5' a. 3' AAG TTT GGG ATA 5' b. 3' TTC AAA CCC TAT 5' c. 5' TTC AAA CCC TAT 3' d.5' UUC AAA CCC UAU 3' e. 3' UUC AAA CCC AUA 5' - CORRECT ANSWER d.5' UUC AAA CCC UAU 3' 4. Starting with the following stretch of tRNAs, write down the DNA template sequence tRNA= 3' AAG UUU GGG AUA 5' a.5' UUC AAA CCC UAU 3' b. 3' UUC AAA CCC UAU 5' c.5' AAG UUU GGG AUA 3' d.3' AAG TTT GGG ATA 5' e.5' AAG TTT GGG ATA 3' - CORRECT ANSWER d.3' AAG TTT GGG ATA 5' 5. What would be a likely consequence of a G protein having GDP permanently attached to it? a.The G protein would be activated when the ligand binds the G protein coupled receptor. b.The G protein would remain in an "off" position and would be unable to relay the signal initiated by the ligand-receptor interaction c.The G protein would operate normally d.The G protein would be turned "on" all the time and be able to relay a signal even in the absence of ligand binding to the G protein coupled receptor e.The G protein would be turned "on" all the time and be able to relay a signal as long as the ligand was bound to the G protein coupled receptor - CORRECT ANSWER b.The G protein would remain in an "off" position and would be unable to relay the signal initiated by the ligand-receptor interaction 6. Myc is a(n)____________ that mediates normal cell division induced by growth factors. When mutations occur resulting in a dysfunctional gene that leads to increased cell division then the mutated gene is called a(n)____________. a. Spliceosome, trasnsgene. b. Trasnsgene, proto-oncogene c. Proto-oncogene, trasnsgene d.Oncogene, proto-oncogene e.Proto-oncogene, oncogene - CORRECT ANSWER e.Proto-oncogene, oncogene 7. What is meant when we say that the codon chart is unambiguous but redundant? a. A single codon can code for multiple amino acids b.A single codon can code for only one amino acid but multiple different codons can code for the same amino acid c.Codons contain one to 3 amino acids d.Genomes are different from one human cell to the next e.Human genomes are similar in one human cell versus another but the genes that are expressed in each may differ - CORRECT ANSWER b.A single codon can code for only one amino acid but multiple different codons can code for the same amino acid 8.________ showed that _________is the transforming component that changed the non-pathogenic R bacteria into pathogenic S bacteria a.Griffith, protein b.Griffith, DNA c.Avery, McCarty, Macleod, protein d.Chargaff, DNA - CORRECT ANSWER c.Avery, McCarty, Macleod, protein 9. When responding to DNA damage, the p53 tumor suppressor protein functions as a __________and binds to the ________ of DNA repair enzyme genes to ______their expression a.Translation factor, start codon, induce b.Translation factor, start codon, reduce c.Transcription factor, primer, induce d.Transcription factor, primer, reduce e.Transcription factor, promoter, induce - CORRECT ANSWER e.Transcription factor, promoter, induce 10. How do DNA nucleotides differ from RNA nucelotides? a.The R groups are different b.DNA contains uracil instead of Adenine c.DNA nucleotides have a hexose sugar while RNA nucleotides have a pentose sugar d.DNA has thymine instead of uracil e.DNA contains, A,U, C, G and RNA contains A, T, C, G - CORRECT ANSWER d.DNA has thymine instead of uracil 11. If a sample of a rabbit DNA contains 15% thymine this means that a.A sample of human DNA would have 30% guanine b.A simple of human DNA would have 15% adenine c.A sample of the same rabbit DNA would have 15% cytosine d.A sample of the same rabbit DNA would have 35% guanine e.The RNA from the rabbit sample would contain 30% adenine - CORRECT ANSWER d.A sample of the same rabbit DNA would have 35% guanine 12. Hershey and Chase used radiolabeled phages to determine whether the genetic material is protein or DNA. what would be the outcome of the experiment if the blender they used malfunctioned and was unable to shear off the phages from the bacteria prior to centrifugation a. the result would be the same b. only phage protein would be found in the cell pellet c. only phage DNA would be found in the cell pellet d. phage protein and DNA would be found in the cell pellet e. phage protein and DNA would be found in the supernatant - CORRECT ANSWER d. phage protein and DNA would be found in the cell pellet 13. when tryptophan levels are high tryptophan serves as the _______ which binds to the ____________ to ___________ transcription. a. activator, tryptophan genes, stimulate b. activator, operator, stimulate c. repressor, operator, inhibit d. co-repressor, operator, inhibit e. repressor, tryptophan genes, inhibit - CORRECT ANSWER d. co-repressor, operator, inhibit 14. why does the DNA double helix have a uniform diameter? a. purines pair with pyrimidines through covalent bonds b. purines pair with pyrimidines through hydrogen bonds c. purines pair with purines through covalent bonds d. purines pair with purines through hydrogen bonds e. pyrimidines pair with pyrimidines through hydrogen bonds - CORRECT ANSWER b. purines pair with pyrimidines through hydrogen bonds 15. lagging strand DNA synthesis requires multiple____________ a. tRNAs b. RNA polymerases c. ribosomes d. promoters e. RNA primers - CORRECT ANSWER e. RNA primers 16. what is the complementary DNA strand to 5' ATT CGG TGA 3' a. 5' AUU CGG TGU 3' B. 3' AUU CGG TGU 5' C. 5' TAA GCC ACT 3' D. 3' TAA GCC ACT 5' E. 3' ATT CGG TGA 5' - CORRECT ANSWER D. 3' TAA GCC ACT 5' 17. the main function of DNA polymerase is to a. synthesize DNA b. seal okazaki fragments together c. unwind DNA d. transcribe DNA e. synthesize proteins - CORRECT ANSWER a. synthesize DNA 18. G protein coupled receptors______________ a. are located in the nucleus of a cell b. are transcription factors that bind directly to DNA c. are transcription factors that bind directly to RNA d. are located on the plasma membrane of a cell e. keep DNA strands apart during DNA replication - CORRECT ANSWER d. are located on the plasma membrane of a cell 19. a ____________ is to transcription as a _____________ is to translation a. primer, promoter b. start codon, primer c. start codon, promoter d. promoter, start codon e. promoter, primer - CORRECT ANSWER d. promoter, start codon 20. You find that the lac repressor contains a mutation that enables it to bind automatically and _____ irreversibly to the operator upstream of the lac operon. How would lactose metabolism be affected when lactose levels rise in the cell. A. The lactose would be metabolized more quickly B. no effect would be observed C. high levels of tryptophan would block lactose metabolism D. the lactose would be metabolized more slowly. E. The lactose would not be metabolized - CORRECT ANSWER E. The lactose would not be metabolized 21. what effect would a nonsense mutation have on protein synthesis? a. no effect b. a longer protein than expected would be generated c. a protein would be the same length as the wild type but would contain multiple different amino acids in the primary sequence d. a shorter protein than expected would be generated e. a protein would be the same length as the wild type but would contain a single different amino acid in the primary sequence - CORRECT ANSWER d. a shorter protein than expected would be generated 22. the pyrimidines are ___________ structures and include ______________ and _________________ a. single ring, thymine, cytosine b. single ring, adenine, guanine c. single ring, thymine, guanine d. double ring, adenine, guanine e. double ring, adenine, thymine - CORRECT ANSWER a. single ring, thymine, cytosine 23. A biochemist isolates and purifies molecules needed for DNA replication. When she adds some DNA, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture? A. DNA ligase B. primase C. Okazaki fragments D. DNA polymerase E. nucleotides - CORRECT ANSWER A. DNA ligase 24. A ________ bond holds the amino acids of a growing polypeptide chain together during the elongation stage of translation. A. hydrogen B. peptide C. glycosidic D. non-covalent E. ionic - CORRECT ANSWER B. peptide 25. When _______________ levels are _____ the lac repressor is ________________ to the operator _____ and _______________ is ________________ A. lactose, low, not bound, lactose, anabolized B. tryptophan, low, bound, lactose, catabolized C. lactose, high, bound, lactose, catabolized D. lactose, high, not bound, lactose, catabolized E. tryptophan, high, bound, lactose, anabolized - CORRECT ANSWER D. lactose, high, not bound, lactose, catabolized 26. What would be the consequence of a mutation that renders the large ribosomal subunit non-functional? a. DNA replication would be inhibited b. transcription would be inhibited c. cell signaling would be blocked d. helicase activity would be inhibitied e. translation would be inhibited - CORRECT ANSWER e. translation would be inhibited 27. Protein _________________ shut down a signal transduction pathway by _________________ proteins. A. kinases, phosphorylating B. kinases, dephosphorylating C. phosphatases, phosphorylating D. phosphatases, dephosphorylating E. kinases, degrading - CORRECT ANSWER D. phosphatases, dephosphorylating 28. A tRNA is charged by the addition of _______________________ A. a mRNA B. a ribosome C. a transcription factor D. a primer E. an amino acid - CORRECT ANSWER E. an amino acid 29. what is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? a. the origins of replication occur only at the 5' end b. helicases and single-strand binding proteins work at the 5' end c. DNA polymerase can join new nucleotides only to the 3' end of a growing strand d. DNA polymerase can join new nucleotides only to the 5' end of a growing strand e. polymerase can work on only one strand at a time - CORRECT ANSWER c. DNA polymerase can join new nucleotides only to the 3' end of a growing strand 30. when evaluating the nature of chromatin, a gene will most likely NOT be expressed when chromatin is in this form a. relaxed b. helixed c. heterochromatin d. euchromatin e. chromatin does not influence gene expression - CORRECT ANSWER c. heterochromatin 31. __________________________ recruit the ____________________________ to ________________ _____ A. primase, primers, polypeptide B. transcription factors, RNA, ribosomes C. transcription factors, DNA, ribosomes D. transcription factors, RNA polymerase, promoters E. transcription factors, DNA polymerase, promoters - CORRECT ANSWER D. transcription factors, RNA polymerase, promoters 32. Assume each of the following letters represents an amino acid. What type of gene mutation occurred to produce the following protein sequence? Normal: JAYBIRDCATPAW Mutated:JAYBIRDBATPAW A) nonsense B) missense C) silent D) sense E) frameshift - CORRECT ANSWER B) missense 33. The term C-terminus refers to the presence of a(n) ________ at one of the ends of a polypeptide. A) collagen B) carboxyl group C) creatine D) carbonyl group E) connexin - CORRECT ANSWER B) carboxyl group 34. From the perspective of the cell receiving the message, the three stages of cell signaling are: _____ A. the alpha, beta, and gamma stages. B. signal reception, nucleus disintegration, and new cell generation. C. signal reception, signal transduction, and cellular response. D. the paracrine, local, and synaptic stages. E. none of the above - CORRECT ANSWER C. signal reception, signal transduction, and cellular response. 35. Which of the following help(s) to stabilize mRNA by inhibiting its degradation? a. RNA polymerase b. TATA box c. introns d. spliceosomes e. 5' cap and poly A tail - CORRECT ANSWER e. 5' cap and poly A tail 36. which enzyme catalyzes the elongation of a DNA strand in the 5' to 3' direction? a. helicase b. DNA ligase c. DNA polymerase d. topoisomerase e. primase - CORRECT ANSWER c. DNA polymerase 37. If an mRNA sequence is 5′AUG-GGC-ACU-CAU3′, what would the anticodon sequence be? A. 3′AUG-GGC-ACU-CAU5′ B. 3′UAC-CCG-UGA-GUA5′ C. 5′AUG-GGC-ACU-CAU3′ D. 5′UAC-CCG-UGA-GUA3′ E. 3′TAC-CCG-TGA-GTA3′ - CORRECT ANSWER B. 3′UAC-CCG-UGA-GUA5′ 38. How many nucleotides are contained in a single codon? _____ A. 1 B. 3 C. 4 D. 6 E. 9 - CORRECT ANSWER B. 3 39. The process that produces mRNA from DNA is called A. transcription. B. translation. C. replication. D. processing. E. post-translational modification. - CORRECT ANSWER A. transcription. 40. ________ is to transcription as ________ are to translation? A. RNA splicesome; ribosomes B. RNA polymerase; ribosomes C. RNA polymerase; RNA splicesomes D. DNA polymerase; RNA polymerase E. DNA polymerase; ribosomes - CORRECT ANSWER B. RNA polymerase; ribosomes 41. The x-ray pictures of DNA taken by this scientist enabled Watson and Crick to build the correct model of DNA. A. Griffith B. Chargaff C. Franklin D. Morgan E. Avery - CORRECT ANSWER C. Franklin 42. 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. 3' AAA-AAT-ATA-ACA 5' D. 3' AAA-GAA-TAA-CAA 5' E. 5' AUG-CTG-CAG-TAT 3' - CORRECT ANSWER D. 3' AAA-GAA-TAA-CAA 5' 43. One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, then activating relay proteins. Which type does this? A. ligand-gated ion channels B. receptor tyrosine kinases C. steroid receptors D. G protein-linked receptor E. testosterone receptor - CORRECT ANSWER B. receptor tyrosine kinases 44. As a ribosome translocates along an mRNA molecule by one codon, which of the following occurs? A. The tRNA that was in the A site moves into the P site. B. The polypeptide enters the E site. C. The tRNA that was in the A site departs from the ribosome via a tunnel. D. The tRNA that was in the P site moves into the A site. E. The tRNA that was in the A site moves to the E site and is released. - CORRECT ANSWER A. The tRNA that was in the A site moves into the P site. 45. All of the following are critical factors for DNA replication on the leading strand EXCEPT? a. primer b. ligase c. polymerase d. primase e. nucleotides - CORRECT ANSWER b. ligase 46. A small molecule that specifically binds to a receptor to initiate a signal transduction pathway A. is called a phosphatase B. is called an enhancer C. is called a terminator D. seldom is involved in hormonal signaling. E. is called a ligand. - CORRECT ANSWER E. is called a ligand. 47. After mixing a heat-killed, fluorescent strain of bacteria with a living non-fluorescent strain, you discover that some of the living cells are now fluorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait? A. DNA passed from the heat-killed strain to the living strain. B. Protein passed from the heat-killed strain to the living strain. C. Both DNA and protein passed from the heat-killed strain to the living strain. D. The fluorescence in the living strain is especially bright. E. Descendants of the living cells are also fluorescent. - CORRECT ANSWER E. Descendants of the living cells are also fluorescent. 48. The general name for an enzyme that transfers phosphate groups from ATP to a protein is A. phosphatase. B. protein kinase. C. protease. D. ATPase. E. ubiquitinase. - CORRECT ANSWER B. protein kinase. 49) You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent A) leading strands and Okazaki fragments. B) lagging strands and Okazaki fragments. C) Okazaki fragments and RNA primers. D) leading strands and RNA primers. E) RNA primers and mitochondrial DNA. - CORRECT ANSWER D) leading strands and RNA primers. 50. The three steps of both transcription and translation are? a. DNA replication, ligation, fusion b. synthesis, dissemination, replacement c. initiation, elongation, termination d. translocation, replication, condensation e. reception, transduction, response - CORRECT ANSWER c. initiation, elongation, termination The maturation of the 5' end of tRNA requires the removal of sequences via 1. tRNA maturase 2. tRNA ligase 3. RNAse T1 4. RNAse P - CORRECT ANSWER 4 Cellular protein synthesis proceeds in which direction? A. carboxyl to amino terminus B. amino to carboxyl terminus C. 3' to 5' D. 5' to 3' - CORRECT ANSWER B Which of the following DNA binding domains are most similar? a. helix-turn-helix AND homeodomain b. helix-loop-helix AND helix-turn-helix c. helix-loop-helix AND homeodomain d. zinc fingers AND homeodomains - CORRECT ANSWER A The 5′-untranslated leader regions of eukaryotic mRNAs often contain multiple 5′-AUG-3′ triplets. Recognition of AUG as start codon usually requires the AUG to be in the context of a. a cap binding complex b. a Kozak consensus sequence c. initiation factors d. molecular chaperones - CORRECT ANSWER B Which of the following mechanisms illustrates a form of transcriptional repression that is unique to eukaryotes? A. repressors blocking binding of sigma factor B. repressors recruiting enzymes to modify groups on histones to loosen chromatin C. repressors recruiting enzymes to modify groups on histones to compact chromatin D. repressors blocking RNA polymerase by binding an operator site within the promoter - CORRECT ANSWER C Can an attenuation mechanism similar to the trp operon function in eukaryotic nuclear gene expression? A.No, transcription and translation must be coupled for attenuation to function in the regulation of gene expression B.No, eukaryotic genes are not located in operons. C.Yes, even thought the eukaryotic transcript must be transported from the nucleus to the cytoplasm to be translated, the attenuator can still form to regulate expression D.Yes, folding of th