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

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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

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

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

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) H (b) H2A (c) H2B (d) H (e) H4 - CORRECT ANSWER (a) H (slide33, Ch 5)

(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

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^ -DNA poly. error rate is 1 in 10^7 base pairs RNA poly.produces 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.

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

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