2023 WGU C785 2nd OA Biochem Final Exam- Questions and Answers

WGU C785 2nd OA Biochem Final Exam 2023 What is the complementary sequence to 3’ ATG CGA ATA 5’? (0/1 Points) 3’ TAT TCG CAT 5’ 3’ TAC GCT TAT 5’ The correct answer is 3' TAT TCG CAT 5'. Remember complementary means “Matching or Pairing” You have to remember to pay attention to your numbers as well as your let ters (A-T, G-C, 5'-3'). The correct answer is 3’ ATG CGA ATA 5’ (original sequence) 5’ TA C GCT TAT 3’ (complementary sequence) But we asked for it in the 3’ direction, so mi rror answer to give correct answer: 3’ TAT TCG CAT 5’ If you chose 3' TAC GCT TAT 5', thi s is incorrect. Although the nucleotides are in the correct order, the 5' and 3' are in the wrong place. DNA strands that are complementary run in opposite directions. This me ans that if one strand starts with a 3', the the complementary strand must start with a 5 '. If none of the answer choices give the correct answer in 5' ---> 3', then you need to wri te its mirror, which will run from 3' ---> 5'. 3’ GAT AGC ATA 5’ 5’ ATA AGC GTA 3’ 2 Which amino acid sequence would result from this Coding DNA strand? 3’ ATG CAG ATA 5’? (1/1 Points) Tyr Val Tyr Ile Gln Ile Ile Asp Val The correct answer is Ile Asp Val. We are starting at the coding strand, and have to remember the relationship between coding DNA and mRNA. These two strands are non- complementary and parallel. So we copy the coding strand , change T ---> U, and then write the mRNA sequence: 3’ ATG CAG ATA 5’ coding 3’ AUG CAG AUA 5’ mRNAMirror by changing orientation: 5’ AUA GAC GUA 3’ Read chart Ile Asp Val (chart is in direction of 5' ---> 3') Leu His Lys 3 Which amino acid sequence would be made from this template DNA strand? 5’ TAT TAC CGA 3’? (1/1 Points) Tyr Tyr Arg Ile Met Ala Ser Val Ile The correct answer is Ser Val Ile because 5’ TAT TAC CGA 3’ template is complementary and antiparallel so 3’ AUA AUG GCU 5’ but it is in the wrong orientation, so mirror 5’ UCG GUA AUA 3’ and read the chart Ser Val Ile Ser His Gln 4 Which of the following are the correct components for a PCR reaction? (1/1 Points) dNTPs, Primer, RNA Polymerase, template RNA dNTPs, Primer, DNA Polymerase, template DNA The correct answer is dNTPs, Primer, DNA Polymerase, template DNA. Notice that all components are about DNA. The Primer is even a DNA Primer. ATP, Primer, mRNA polymerase; template mRNA Acetyl CoA, RNA primer, DNA Ligase, Template phosphate 5 Assuming 100% reaction efficiency, how many DNA copies will be produced after 5 PCR cycles, if we begin with 1 DNA template? (1/1 Points) 16 32 The correct answer is 32. 2x2x2x2x2=32 64 10 6 Which of the following would represent a silent mutation if this is the original sequence: 5’ AUC GUA ACA 3’? (1/1 Points) 5’ AUC GGA ACA 3’ 5' AUA GUA ACA 3' The correct answer is 5' AUC GUA ACA 3' Ile Val Thr 5’ AUG GUA ACA 3’ 7 If the original coding sequence is 5’ CGA TAC TTC AGA 3’ and it is mutated to 5' CGA TAT TTC AGA 3', what type of mutation would have taken place? (1/1 Points) 5’ AUC GCA ACA 3’ Silent The correct answer is silent mutation. The nucleotide sequence changes, but it codes for the same amino acid. The coding sequence 5' TAC 3' corresponds to the mRNA sequence 5' UAC 3' (Tyr), and the coding sequence 5' TAT 3' corresponds to the mRNA sequence 5' UAU 3' (Tyr). Since the C changed to at T, this is a point mutation. If the point mutation results in the same amino acid in the new sequence as in the original sequence, the point mutation is a silent mutation. Missense Nonsense Insertion 8 Huntington's is an autosomal dominant disorder. Which of the following chromosome pairs would be inherited by a person with Huntington's Disease? (Yellow box = Dominant allele, Green box = Recessive allele) (1/1 Points) Option 1 The correct answer is Option 1 because an autosomal dominant disorder would be inherited on numbered chromosomes, not sex chromosomes X or Y. Also, at least one dominant allele (yellow box) needs to be present for the individual to have the dominant disease. Option 2 Option 3 Option 4 9 The pedigree below tracks Duchenne Muscular Dystrophy (DMD) through several generations. What type of inheritance does DMD express? (1/1 Points) Autosomal dominant Autosomal recessive X-linked Dominant X- Linked recessive The correct answer is X- linked recessive because parents (carriers) do not have it (II-5- 6) but a child does (III-5). You will get the same result if you consider parents (carriers) (I-1-2), who do not have the trait, but a child does (II-3). A third option that gives the same result (X-linked recessive) is by considering parents (carriers) who do not have the trait (III-1-2), and their child does (IV-1). The pattern is recessive because the selected parents are carriers, and it is X-linked because only males have the trait. 10 If you had a mother who is homozygous for a recessive disease, and a father who is a heterozygous carrier, what percentage of children will have the disease? (1/1 Points) 0% 25% 50% The correct answer is 50%. Homozygous recessive: aa Heterozygous: Aa When you see "percentage" or "probability," think Punnett square. 50% of the children would be expected to be Aa, and 50% of the children would be expected to be aa. 75% 100% 11 Which of the following describes an epigenetic change? (0/1 Points) Denaturation of template DNA to facilitate primer annealing. Increased methylation of the promoter region of a tumor suppressor gene in a de veloping fetus. Thymine dimer formation resulting from UV radiation. Mismatch mutation caused by mistakes made by DNA Polymerase during replication. The correct answer is "Increased methylation of the promoter region of a tumor suppressor gene in a developing fetus." 12 Rett syndrome is a brain disorder that occurs almost exclusively in females, causing severe deficits in language, learning, coordination and other brain functions. Decreased expression of the MECP2 gene causes Rett syndrome. Which of the following scenarios correctly describes how Rett syndrome could be developed? (1/1 Points) A DNA-binding protein blocks RNA Polymerase from binding to the promoter sequence, facilitating the transcription of the MECP2 gene. Transcription factors are unable to bind to the transcription start site of the MECP2 gene because nucleosomes are tightly packed together. The answer is "Transcription factors are unable to bind to the transcription start site of the MECP2 gene because nucleosomes are tightly packed together." Think "increased space gives increased access and increased expression." Gene expression is increased when nucleosomes are widely spaced and transcription factors and RNA Polymerase are able to bind to the transcription start site of the gene. In this question, decreased expression is resulting from decreased space between the nucleosomes, so the RNA Polymerase and transcription factors have decreased access to the transcription start site of the gene. Transcription activators cause nucleosomes to separate, exposing the MECP2 gene. RNA Polymerase binds to the MECP2 gene and begins translation. 13 What happens when the incorrect base is added during the synthesis of a DNA strand in DNA replication? (1/1 Points) The homologous chromosome is used to replace the incorrectly added base with the correct one. DNA Polymerase removes the incorrect base and adds in the correct base. The correct answer is "DNA Polymerase removes the incorrect base and adds in the correct base." DNA Polymerase repairs mismatch errors that occur during DNA replication. Thymine dimers occur. Distortion of the double helix occurs and is repaired by RNA Polymerase. 14 What is the correct definition of nucleotide excision repair? (1/1 Points) Removal of a single damaged nucleotide Damage to a few or several nucleotides are identified, then many nucleotides are removed and all are replaced to repair the DNA segment The correct answer is "Damage to a few or several nucleotides are identified, then many nucleotides are removed and all are replaced to repair the DNA segment." In nucleotide excision repair, several nucleotides are removed whereas, in BER (base excision repair), a single nucleotide is removed. Required when there are breaks in the double stranded DNA strand which causes discontinuity in both strands Insertion of a thymine dimer 15 If arginine is mutated to leucine within a protein, how would the structure of the protein be affected? (1/1 Points) Ionic bonds will continue to form, allowing the protein to fold as normal. Hydrophobic interactions will continue to occur resulting in normal folding. Ionic bonds will no longer form, potentially causing the protein to misfold. The correct answer is "Ionic bonds will no longer form, potentially causing the protein to misfold." Since arginine is a positively-charged amino acid, it would have formed an ionic bond with a negatively-charged amino acid in the protein. Leucine is not charged and is hydrophobic, so it will not form this same ionic bond, and could lead to protein misfolding. Hydrophobic interactions will be broken, potentially causing aggregation. 16 Which pair of amino acids below could bond together to stabilize the tertiary structure of a protein? (1/1 Points) Option 1 Option 2 Option 3 The correct answer is "phenylalanine" and "methionine." Phenylalanine and methionine are both nonpolar (hydrophobic) amino acids, and they interact in the core of the protein through hydrophobic forces. If you chose, "Glutamine" and "Alanine," this is an incorrect answer. Glutamine is a polar amino acid, which should form a hydrogen bond to another polar amino acid, and alanine is a hydrophobic amino acid, which should interact with another hydrophobic amino acid to form hydrophobic interactions. Option 4 17 On a hot summer's day, I was cleaning my garage. My cat Sophie was out with me, and got into a bottle containing a strong reducing agent. Of course I took her straight to the vet. What type of amino acid bonds would be disrupted by exposure to the strong reducing agent? (1/1 Points) Hydrophobic interactions Hydrogen bonds Disulfide bonds The correct answer is covalent (disulfide) bonds. Hydrophobic interactions are disrupted by heat. Hydrogen bonds and ionic bonds are both disrupted by pH and by salt. Ionic bonds 18 What type of bond can the amino acids below form to stabilize the tertiary structure of a protein? (1/1 Points) Ionic bond Hydrophobic interaction Hydrogen bond Message for respondents who select this answerThe correct answer is "hydrogen bond." Each of the amino acids shown is a polar amino acid, and polar amino acids interact through hydrogen bonds. The NH combined with the C=O in glutamine places this amino acid side chain into the polar category. The OH bond in serine places this amino acid side chain into the polar category. Disulfide bond 19 What type of reaction forms the primary structure of a protein? (1/1 Points) Activation energy Enzymes Dehydration The correct answer is a dehydration reaction. When two amino acids join together, they lose water. One loses an O from a carboxyl group, and the other loses two Hs from its amino group, to give a loss of water. See Study Guide Step 7 for review. Hydrolysis 20 Myoglobin is an oxygen storage protein and exhibits a hyperbolic curve in an oxygen saturation graph. What is the highest level of protein structure exhibited by myoglobin? (1/1 Points) Primary Secondary Tertiary The correct answer is "tertiary." Myoglobin is made from one polypeptide chain, or is a "single subunit" protein. Myoglobin's tertiary structure gives it its functional 3D shape. A hyperbolic curve indicates a "single subunit" protein. A sigmoidal curve indicates a quaternary (multi-subunit) protein. Quaternary 21 What level of protein structure involves alpha helices and beta pleated sheets? (1/1 Points) Primary Secondary The secondary level has alpha helices and beta pleated sheets. Primary structure is formed by joining together amino acids through peptide bonds. Secondary structure is formed by hydrogen bonds between backbone amino acids.Tertiary structure is formed form interactions between amino acid side chains. Quaternary structure is formed from interactions between amino acid side chains. Proteins with quaternary structure have two or more subunits. Tertiary Quaternary 22 Glutamine is located at position 13, of a protein, and forms a hydrogen bond with the amino acid at position 89. What would happen if the amino acid at position 89 was mutated to alanine? (1/1 Points) Nothing they will bind normally The hydrogen bond will no longer be formed, and the protein will be misfolded The correct answer is "The hydrogen bond will no longer be formed, and the protein will be misfolded. Glutamine is a polar amino acid (NH and also C=O), and alanine is a nonpolar (hydrophobic) amino acid (CH3), and so alanine will not interact with the polar amino acid glutamine. Nothing, they will form a hydrophobic interaction They will form a disulfide bond 23 An elderly patient is diagnosed with Alzheimer’s Disease. Which of the following is most likely the cause of this neurological disorder? (1/1 Points) Disulfide bond formation by cysteine amino acids Iron deficiency Aggregation of hydrophobic amino acids The correct answer is "Aggregation of hydrophobic amino acids." Alzheimer's disease results from abnormal protein aggregation in the brain. Ionic bonds formed by hydrogen bonding of amino acids 24 What type of interactions would be affected in a patient with diabetic ketoacidosis? (select all that apply) (1/1 Points) Hydrogen bonds Hydrogen bonds and ionic bonds are affected by a change in pH. Hydrogen bonds and ionic bonds are also affected by a change in salt concentration. Ionic bonds Hydrogen bonds and ionic bonds are affected by a change in pH. Hydrogen bonds and ionic bonds are also affected by a change in salt concentration. Hydrophobic interactions Disulfide bonds 25 Hydrogen bonds between backbone groups stabilize what level of protein structure? (1/1 Points) Primary Secondary The correct answer is "secondary." Primary structure is formed by joining together amino acids through peptide bonds. Secondary structure is formed by hydrogen bonds between backbone amino acids. Tertiary structure is formed form interactions between amino acid side chains. Quaternary structure is formed from interactions between amino acid side chains. Proteins with quaternary structure have two or more subunits. Tertiary Quaternary 26 What type of bond is found in the primary structure of a protein? (1/1 Points) Ionic Disulfide Charged Peptide The correct answer is "peptide bonds." The primary structure is built by hooking together amino acids to make the amino acid backbone of the protein. The amino acids are joined together by peptide bonds. 27 Which of the following is true about protein structure and function? (1/1 Points) A protein has optimal function in its primary structure. All proteins carry out cellular functions when they have obtained their final quaternary structure. Ionic bonds between the backbone groups of amino acids stabilize a protein's tertiary structure. The hydrophobic effect primarily contributes to a single subunit protein's tertiary structure. The correct answer is "the hydrophobic effect primarily contributes to a single subunit protein's tertiary structure." The hydrophobic effect drives the formation of the core of a protein, which is the predominant contributing factor to the protein's tertiary structure. 28 Frying an egg in a pan changes the egg white color, due to the protein ovalbumin, from translucent to white. Which bond or interaction is most likely to be disrupted within the Ovalbumin? (1/1 Points) Ionic bonds Hydrophobic interactions The correct answer is "Hydrophobic interactions." Heat will disrupt hydrophobic interactions. Ionic bonds are disrupted by changes in pH and by salt, and disulfide bonds are disrupted by reducing agents. Disulfide bonds None of the above 29 Which of the following statements correctly describes the difference between hemoglobin and myoglobin? (1/1 Points) Hemoglobin binds oxygen in a cooperative manner, while Myoglobin binds oxygen with a relatively higher affinity and stores oxygen. The correct answer is, "Hemoglobin binds oxygen in a cooperative manner, while Myoglobin binds oxygen with a relatively higher affinity and stores oxygen." Hemoglobin has 4 subunits and binds oxygen in a cooperative manner. Cooperativity means that as one molecule of oxygen binds to hemoglobin, the shape of hemoglobin changes to make it easier to bind subsequent molecules of oxygen. Myoglobin’s job is to store oxygen, so it binds to oxygen with a high affinity and stores it. Hemoglobin has tertiary structure, while Myoglobin has quaternary structure and binds oxygen in a cooperative manner. Hemoglobin stores oxygen and Myoglobin delivers oxygen to oxygen-deprived muscle tissue. Myoglobin is bound by 2,3-BPG and changes into the T-state to deliver oxygen 30 Which of the following molecules binds directly to the iron in hemoglobin? (1/1 Points) CO2 Mg 2,3-BPG CO CO does bind directly to the iron in hemoglobin, taking the place of oxygen in subunit bound CO 31 Susie is 18 weeks pregnant with twins and was recently diagnosed with gestational diabetes. Susie’s twins are developing according to schedule and Susie hopes to carry the twins as close to full term as possible. Which statement below describes how a sufficient amount of oxygen is made available to Susie’s developing fetuses? (1/1 Points) Bicarbonate binds to Susie’s hemoglobin and stabilizes the T-state conformation, which favors the delivery of oxygen to the developing fetuses. 2,3-BPG binds to Susie’s hemoglobin and stabilizes the T-state conformation, which favors the delivery of oxygen to the developing fetuses. The correct answer is, "2,3-BPG binds to Susie’s hemoglobin and stabilizes the T-state conformation, which favors the delivery of oxygen to the developing fetuses." 2,3-BPG binds to hemoglobin and stabilizes the T-state which favors oxygen delivery. Carbon monoxide binds to Susie’s hemoglobin and stabilizes the R-state conformation, which increases the delivery of oxygen to the developing fetuses. Bicarbonate induces Susie’s hemoglobin to adopt a non-planar conformation and bind oxygen so that the developing fetuses are sufficiently oxygenated. 32 Alex is preparing to run in his first 5K. As he stretches, his muscles are producing ATP through aerobic metabolic pathways. A byproduct of a functioning citric acid cycle is carbon dioxide. How is this carbon dioxide removed from the body? (1/1 Points)