BIO FINAL EXAM
SLC24A5 is a protein that is associated with skin pigmentation. The SLC24A5 gene encodes a transport protein. The human ancestral version of this gene leads to dark pigmentation whereas a subsequent mutation resulted in a second version that leads to light pigmentation. Using the diagram below containing parts of the DNA sequences of the two alleles of the SLC24A5 gene, compare the amino acid sequences for SLC24A5*1 and SLC24A5*2 and identify the type of mutation in SLC24A5*2? SLC24A5*1 5'-GTT GCA GGC GCA ACT TTC-3' 3'-CAA CGT CCG CGT TGA AAG-5' SLC24A5*2 5'-GTT GCA GGC ACA ACT TTC-3' 3'-CAA CGT CCG TGT TGA AAG-5'
missense mutation
Which of the following cell models is a correct illustration of metaphase I for a 2n = 4 cell?
model w/ 4 duplicated chromosomes (2 sets of homologous chromosomes-each lined up at the metaphase plate)
Which structural formula depicts a deoxyribonucleotide? (shows diagram)
nucleotide with a 5 sugar with no hydroxyl on the 2' carbon
Alternative splicing during gene expression occurs _____.
only inside the nucleus in eukaryotes
In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision repair mechanism. These individuals are unable to repair DNA damage caused by ultraviolet light. Which of the following are the most prominent types of DNA lesions in individuals suffering from xeroderma pigmentosum?
thymine-thymine dimers
Put the following events of bacterial transcription in chronological order. 1.) Sigma binds to the promoter region. 2.) The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands. 3.) Sigma binds to RNA polymerase. 4.) Sigma is released. 5.) Transcription begins.
3, 1, 2, 5, 4
Axonemal dyneins are responsible for the movement of cilia and flagella, whereas cytoplasmic dynein facilitates movement of organelles and other cargo, just like kinesin. These motor proteins, dynein and kinesin, walk on microtubules carrying their cargo. If a cell receives a vesicle by endocytosis, which motor protein would deliver the vesicle to its destination in the cell and how?
Dynein walking towards the minus end of the microtubule
A mutation occurs that leads to hyper-expression of MPF. How would this affect the rate (time it takes to complete) at which mitosis occurs?
Decrease the rate
Which molecule becomes reduced in the following chemical reaction? Glyceraldehyde phosphate + NAD+ → diphosphoglycerate + NADH + H+
NAD+
The flow of electrons involved in oxidative phosphorylation can be described as _______.
NADH/FADH2 --> Electron transport chain --> O2
Which of the following statements is TRUE about enzyme-catalyzed reactions?
The reaction is faster than the same reaction in the absence of the enzyme
Which of the following is the strongest evidence that protein structure and function are correlated?
Denatured (unfolded) proteins do not function normally.
Eukaryotic genomes have gene sequences that can code for more than one polypeptide sequence because _____.
Different introns can be cut out of the pre-mRNA
Which of the following is NOT a way to control Cyclin-CDK activity?
Dimerization of cyclins
In a 'pulse-chase' experiment, radioactively labeled amino acids are fed to a culture of bacteria, and then the bacteria are added to a culture of macrophages (white blood cells). Which motor protein would be responsible for transporting the resulting vesicles?
Dynein
The proteins dynein and kinesin 'walk' along microtubules carrying cargo. Which of the following is most likely:
Dynein and kinesin are ATPases.
An enzyme-catalyzed reaction has G of -20 kcal/mol. If you double the amount of enzyme, what will be the new G?
-20 kcal/mol
Protein A is a digestive enzyme that fails to be sent from the Golgi body to the lysosome because of a defect. Propose a change in Protein A that could cause failure to reach a lysosome. Explain the process normal Protein A will follow to be directed to a lysosome and then identify the failure.
-Protein A must contain an ER signal sequence which will allow it to be synthesized in the RER. -Protein A will be transported from RER to Golgi in a vesicle by (kinesin walking on microtubules) -Golgi will tag Protein A with (a mannose-6-phosphate), directing it to the lysosome -Protein A will leave Golgi (in a vesicle) headed for lysosome -The mutation in Protein A may cause the Golgi to tag it incorrectly, therefore not allowing it to be transported to the lysosome. (Other reasonable explanations accepted.)
The amino acid Proline (Pro) can be encoded for by four codons: CCC, CCU, CCG, and CCA. What two features of the genetic code does this highlight?
-The redundancy of codons and the third base 'wobble' -The conservation of bases in codons encoding for the same amino acid
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base- pairing rules?
A + G = C + T
Select the complementary strand of 3'-ATTAGCACT-5'
3'-AGTGCTAAT-5'
A solution with a pH of 5 has how many more protons in it than a solution with a pH of 7?
100 times
Put the following steps of DNA replication in chronological order: 1.) Single-stranded binding proteins attach to DNA strands. 2.) Hydrogen bonds between base pairs of antiparallel strands are broken. 3.) Primase binds to the site of origin. 4.) DNA polymerase binds to the template strand. 5.) An RNA primer is created.
2, 1, 3, 5, 4
Which of the following best describes the input and output of the sodium/potassium pump?
3 Na+ out, 2 K+ in
If a double-stranded DNA sample were composed of 20% adenine, what would be the percentage of cytosine?
30
A solution with a hydrogen ion concentration of 0.0001 M has a pH of ________, and is therefore _________.
4, acidic
If a double-stranded DNA sample was composed of 10 percent thymine, what would be the percentage of guanine?
40
What wavelength of light in the accompanying figure is most effective in driving photosynthesis? (diagram showing absorbance of chlorophyll and rate of photosynthesis- both are directly related but look solely at the photosynthesis line for this) (all wavelength in mm: violet 400, blue about 480, green about 530 and yellow 560, orange about 625, red about 680)
420 mm (remember that photosynthesis is lowest at yellow and green, that's why leaves are green- that's the wavelength reflected)
How many amino acids are in the protein coded by the following DNA template strand? 3'-GCAGCTACGCTACCGGACGTATCGCAT-5' (just do comp base pairing to get mRNA, start at AUG and stop at the stop codon- remember that the stop codon is not an amino acid but the start codon is)
5
If one strand of a DNA molecule has the sequence of bases 5' ATTGCA 3', the other complementary strand would have the sequence ________.
5' TGCAAT 3'
If the sequence in the non-coding strand of DNA for a particular amino acid is 5' TCG 3' (template strand), then the anticodon on the corresponding tRNA is
5' UCG 3'
Given the double-stranded DNA shown below, RNA is synthesized in the ____________ direction by RNA polymerase using _________________. DNA template strand 5' ________ 3' DNA nontemplate strand 3' ________ 5'
5' → 3', the template DNA strand
If one strand of a DNA molecule has the sequence of bases 5'-ATTGCA-3', the other complementary strand would have the sequence _____.
5'-TGCAAT-3'
If the sequence in the coding strand of DNA for a particular amino acid is 5'AGT3', then the anticodon on the corresponding tRNA would be ________.
5'ACU3'
A cell has 6 unreplicated chromosomes. How many replicated chromosomes does the cell have after chromosome replication?
6
A particular polypeptide was found to contain 100 amino acids. How many peptide bonds are present in this protein?
99
A bacterium that lives in the acidic human stomach has a mutation in a gene encoding for acid survival. This mutation occurs when the codon CCC, encoding for Proline, changes to ACC, encoding for Threonine. This causes the bacterium to succumb more quickly to the acidic environment. What would this be an example of?
A deleterious missense mutation
The partial negative charge at one end of a water molecular is attracted to the partial positive charge of another water molecule. What is this attraction called?
A hydrogen bond
A cell has defective Ras protein. Which of the following is most likely?
A signal molecule will bind a Receptor Tyrosine Kinase, but the interior of the cell will not be phosphorylated.
Which of the following best describes the tertiary structure of RNA molecules, such as ribozymes?
A single nucleotide strand where multiple "stem and loop" structures begin to interact
Refer to the figure below. After denaturation and primer annealing, what nucleotides will be added during the extension step in the polymerase chain reaction (PCR) and what type of primer will they be added to? The nucleotides should appear in the new strand in the order that they will be added starting at the 3′ end of the primer. 3' HO-BACKBONE G A A T C T G C T G C T T PRIMER. TEMPLATE 5'- -3'-OH
A, G, A, C, G, A, C added to a DNA primer
Yeast cells grown anaerobically can obtain energy by fermentation. Which is not a product of this process?
ADP
Damage to a chloroplast has disrupted the thylakoid membrane, causing many breaks and holes. Which of the following should you predict to occur first
ATP synthase would stop turning and stop producing ATP
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of _____.
ATP, CO2, and ethanol (ethyl alcohol)
A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion concentration of 10-7M while the concentration in the SR is 10-2M, then how is the ATPase acting?
ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
Protein phosphorylation is commonly involved with all of the following except
Activation of G protein-coupled receptors
If you wished to block mitosis at Anaphase (but NOT other stages of mitosis), which of the following could you do?
Add a toxin that prevents separation of the centromeres
If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to:
Add more of the enzyme
Normal hemoglobin is a tetramer, consisting of two molecules of β-globin and two molecules of α-globin. In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits _______.
Altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered
Scientists studying transcription in yeast (Saccharomyces cerevisiae) created an experimental strain that produced a modified RNA polymerase containing a single amino acid substitution. The scientists determined the maximum elongation rate during transcription with and without the modified RNA polymerase enzyme (Figure 1). The compound amanitin, which is commonly found in toxic mushrooms, is a specific RNA polymerase inhibitor. Amanitin binds to the RNA polymerase active site and inhibits transcription. In a second experiment, the scientists treated the wild-type and experimental strains of S. cerevisiae with a 40 μg / mL solution of amanitin and recorded the maximum elongation rate of the mRNA (Figure 2). (diagram shows significantly large decrease for wild strain and a very small decrease in experimental strain)
Amanitin decreases the maximum elongation rate for the wild strain and does not affect the rate in the experimental strain.
Canine phosphofructokinase (PFK) deficiency afflicts Springer spaniels, affecting an estimated 10 percent of the breed. Given its critical role in glycolysis, one implication of the genetic defect resulting in PFK deficiency in dogs is ________.
An intolerance for exercise
A cell undergoing mitosis in a small mammal contains eight chromosomes. During which phases of the cell cycle will this cell contain 16 chromosomes?
Anaphase and telophase
After doing an analysis of your chromosomes, a lab identified an allele called MHY7, which codes for a muscle contraction protein, on your chromosome 14. Which of the following must be true?
At least one of your parents must have the MHY7 allele on their chromosome 14.
Where is the start codon located in the structure below? (diagram showing a mature eukaryotic mRNA)
At the downstream end of the 5' untranslated region (UTR)
Recall from the "Mystery of the Newt" (Lectures 1 & 2) that a single newt killed three hunters after it got into their coffee pot. As the newt was boiled over the campfire, a substance on its skin—called tetrodotoxin (TTX)— contaminated the water to make a lethal brew. How did TTX kill the hunters? In the early 1960s, researchers determined that TTX interferes with the activity of nerve and muscle tissue by binding to a sodium ion channel in the plasma membranes of nerve cells. Research on the structure of voltage-gated sodium channels revealed that TTX binds to certain amino acid residues in the pore of the channel, interfering with its normal function. In the absence of functional voltage-gated sodium channels, signals between the brain and muscles are disrupted and the campers likely died of either respiratory or heart failure. Cells use the sodium electrical gradient to perform many activities. What membrane protein is used to establish the sodium electrochemical gradient and how does it work?
B. The sodium-potassium pump (Na+/K+-ATPase) establishes the sodium electrical gradient by using ATP to undergo conformational changes that result in moving three sodium ions out of the cell and two potassium ions into the cell.
Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) is the enzyme that catalyzes the fixation of CO2 to RuBP. Rubisco also catalyzes the reaction of O2 with RuBP, leading to photorespiration, a process counterproductive to photosynthesis. What adaptations are found in C4 or CAM systems to reduce photorespiration?
Both fix CO2 to PEP prior to fixation by the Calvin cycle
When the sugars in barley, rice, corn, or grapes are fermented, they produce ethanol and carbon dioxide. Today, ethanol is harvested to use as engine fuel. The ethanol formed during fermentation contains a great deal of energy because it still contains some _____.
C-H bonds that can be oxidized
What physical property is associated with the chemical differences between saturated and unsaturated fats?
C=C bonds normally result in kinks that increase the spacing between fats and thus make unsaturated fats more fluid than saturated fats.
Which of the following is most likely to cross a cell membrane through simple diffusion?
Carbon dioxide
What four elements make up a majority of living matter?
Carbon, oxygen, nitrogen, hydrogen
Cells get past cell-cycle checkpoints by _____.
Cdks bound to cyclins phosphorylating other proteins
DNA, like RNA, has different levels of structure. Which of these bonds is involved in stabilizing double-helix structure
Complementary base-pairing
Steroid hormones bind to receptors inside the cell and alter their conformation. The hormone-receptor complex is then transported into the nucleus, where it can directly bind DNA and affect gene expression. To get from the location where the receptor binds the hormone to its site of action, the hormone-receptor complex must ________.
Contain and NLS (nuclear localization signal)
A mutation occurs that leads to Ras protein being permanently bound to GTP, what occurs?
Continually signals for downstream transcription events & cellular growth
What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?
Continuous transcription of operon's genes
Cortisol is a hormone derived from cholesterol. When Cortisol is added to the extracellular fluid near a particular cell, that cell increases the expression of a Protein S. Based on this information, it is most likely that:
Cortisol binds to an intracellular receptor (cytoplasmic receptor) that is a transcription factor that binds directly to DNA.
Imagine that a woman is heterozygous for a color blindness allele. At a site on the chromosome with the color blindness allele, a new mutation occurs that causes ALD, creating one chromosome with an allele for color blindness and an allele for ALD. A son of this woman is color-blind but does not have ALD. Assuming that no new mutations have occurred, what could account for this color-blind son without ALD?
Crossing-over
A drug Semderivir blocks the function of actin. Which part of the animal cell cycle would be me most disrupted?
Cytokinesis & cleavage furrow formation
When cell division is not controlled, tumors will develop which may lead to cancer. Different drugs are used to treat cancer and they affect different aspects of the cell cycle. Cytochalasin B blocks the function of actin and colchicine (derived from autumn crocus plants) binds to tubulin. Which of the following aspects of the cell cycle would be most disrupted by cytochalasin B and colchicine, respectively?
Cytokinesis and spindle formation
Mature red blood cells lack internal organelles, including a nucleus. Yet they transport the life-giving O2 molecule to all cells in the human body. This suggests that the shape of these cells must be flexible. What do you suspect is responsible for this flexible shape?
Cytoskeleton
Scientists experimentally modified the Phosphofructokinase (PFK) gene so that it would contain both a nuclear localization signal and an ER signal sequence. What is the normal location of PFK and its possible new location, respectively?
Cytosol; ER
Which of the following is most likely to lead to cancer?
GTP being constantly bound to Ras
How is it possible for this blond/dark hair enhancer to regulate transcription of a gene coding region that is so far away?
DNA looping and protein-protein interactions bring the enhancer physically close to the promoter.
How would DNA replication change if a cell had very low levels of Primase?
DNA replication would slow down. With low amounts of primase, RNA primers would be added to single-stranded DNA more slowly. RNA primers are required for the attachment of DNA Polymerase III.
Cancer changes gene expression of p53. Because this mechanism is found in many cancer types, it must affect _____.
DNA sequences
This table gives the results of assays of percentages of bases from nucleic acids isolated from different sources. The nucleic acid from source 3 is ______ and _____. A G T C (3) 20 20 30 30
DNA; single stranded
A mutation occurs that inactivates Retinoblastoma protein (Rb) via hyperphosphorylation. Which of the following biomedical treatments is best suited to fight the adverse effects of the mutation?
E2F inhibitors
Chondrocytes are cells found in the cartilage in our joints. In some forms of osteoarthritis, destruction of chondrocyte cellular matrix is associated with a diseased Endoplasmic reticulum. This finding supports the idea that
ER is involved in the synthesis of extracellular matrix
You have discovered an enzyme that can catalyze two different chemical reactions. Based on this information, which of the following is most likely to be correct?
Either the enzyme has two distinct active sites, or the reactants involved in the two reactions are very similar in size and shape.
Proteins that interact with DNA often interact with the phosphates that are part of this molecule. Which of the following types of amino acids would you predict to be present in the part of the protein that interacts with the phosphates in DNA? (remember that phosphate group has a negative charge - acidic)
Electrically charged/basic amino acids
There are two M-phase checkpoints. Which of the following would cause the cell to arrest in M-phase?
Elevated levels of MPF
Which of the following best describes actin treadmilling?
Equal rates of depolymerization at minus end & polymerization at plus end
Which of the following is most likely to lead to cancer?
GTP beng constantly bound to Ras
Insulin is a peptide hormone produced by beta cells of the pancreas. It helps control blood glucose levels by signaling the liver, muscle and fat cells to take in glucose from the blood to be used for energy. Using this information, which transport mechanism is most probably functioning in the pancreatic beta cells?
Exocytosis
Which of the following is not true of RNA processing?
Exons are cut out before mRNA leaves nucleus
Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
Facilitated diffusion
Ions can easily cross the lipid bilayer (T/F)
False
Peptide bonds are broken when a protein is denatured (T/F)
False
The presence of double bonds increases the strength of the hydrophobic interactions in lipid bilayers, and thus makes them less permeable to polar molecules. (T/F)
False
You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After recording the degree of permeability of this membrane to glucose (there was some permeability), you increase the proportion of unsaturated phospholipids in the bilayer. This bilayer is now permeable to ions. (T/F)
False
Are telomeres, and the telomerase enzyme that builds telomeres, the "fountain of youth" that could give us a longer lifespan? All of our cells contain the gene for making telomerase. It is simply a matter of whether that gene is "switched on" so the cell makes telomerase, or "switched off" so the cell no longer produces telomerase. All cells in a developing embryo have the gene switched on, while most of the cells in an elderly person have the gene switched off. "Switched on" means the process of gene expression, in which the gene is transcribed into mRNA and then translated into protein. Would we humans live longer if our cells produced more telomerase? It turns out that there are no simple answers. Cancer cells generally have the telomerase gene switched on, which allows them to divide at a rapid pace and create tumors. To have the telomerase gene suddenly switched on in all of our cells, or to flood our cells with a medication containing telomerase, could backfire. Instead of giving normal cells a jump-start to help them start dividing again, the presence of telomerase could trigger precancerous cells to behave like full-blown cancer cells. Our choice would then become one of preferring to die of old age, or to die from cancer. Would you want to greatly increase your risk of certain death from cancer in an effort to live longer? Perhaps the question we should be asking is not whether we can live longer with the help of telomerase, but rather if we can use our understanding of telomerase to cure cancer. Cancer cells continue to divide because the gene for producing telomerase gets turned back on. Perhaps we could find a way to turn off that gene in cancer cells. Or perhaps we could find a drug that binds to telomerase, so that cancer cells can no longer rebuild their telomeres. Either way, cancer cells would continue to divide during these treatments, but only until their telomeres were gone, and then tumors would theoretically stop growing. But here's one more complicating factor in finding an easy cure for cancer: naked mole rats produce more telomerase than other rodents or humans, and often live for 30 years (compared with mice who live about 3 years) but they don't develop cancer. In 2013, it was discovered that the cells of naked mole rats produce an extracellular matrix (the sticky coating on the outside of many cells) with much larger proteins than the extracellular matrix of other rodents or humans. These large proteins help prevent their cells from overcrowding and forming tumors. So, don't expect to see a cure for cancer on drug store shelves tomorrow. Cancer is complex, with a variety of triggers and control mechanisms, and it will take additional research on a variety of organisms until we completely understand all forms of cancer, and how to stop cancer in its tracks. Which of the following has the greatest potential as a cancer treatment?
Find a way to switch off the gene for making telomerase in cancer cells, since the cells would stop dividing when the telomeres were gone
CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they ________.
Fix CO2 into organic acids during the night
Why is RNA function so versatile?
Fold into lots of complex structures bc it's not as structurally stable
How many electrons are involved in a double covalent bond?
Four
Which of the following statements about mutations is true?
Frameshift mutations only occur in the protein-coding region of a gene.
A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell is in:
G1
Which statement is true of the following reaction? C6H12O6 + 6 O2 ---> 6 CO2 + 6 H2O
Glucose carbons are oxidized to carbon dioxide
The membrane protein labeled "A" in the image below is a Glucose transporter (carrier protein). What might you expect about the movement of Na+ and/or glucose across the cell membrane? (picture showing glucose and sodium concentration higher on the outside of the cell than the inside)
Glucose would likely move from the outside of the cell to the inside.
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
Glycolysis
Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be yellowish green. What wavelengths of visible light are reflected by this pigment?
Green and yellow
The human stomach contains a natural, carbohydrate-based antibiotic that probably protects a large portion of the population from various diseases caused by the bacterium Helicobacter pylori. This bacterium has been linked to peptic ulcers, gastritis, and stomach cancer. This naturally occurring antibiotic is described by researchers as having a terminal α-1, 4-linked N-acetylglucosamine (NAG), and it acts by inhibiting the biosynthesis of a major component of the cell wall in H. pylori. Researchers created a glycoprotein with a terminal NAG (that is, a protein with NAG attached to its end). Their hypothesis is that the terminal NAG, and not the protein component, is responsible for the damage to the cell wall in H. pylori. What would be the most appropriate control for testing this hypothesis?
Grow H. pylori in a test tube with a glycoprotein that has its terminal NAG removed.
Which of the following sequences correctly represents the flow of electrons in the light capturing reactions?
H2O → photosystem I → NADPH
Which of the following is not a function of the extracellular matrix?
Helps cancer cells metastasize
Which type of interaction stabilizes the α-helix and the β-pleated sheet structures of proteins?
Hydrogen bonds
PrPc has more α-helices than the infectious prion protein. What type of bond is directly involved in the formation of an α-helix?
Hydrogen bonds between amino acid residues
The R-group, or side chain, of the amino acid serine is -CH2-OH. The R-group, or side chain, of the amino acid leucine is -CH2-CH-(CH3)2. Where would you expect to find these amino acids in a globular protein in aqueous solution?
Leucine would be in the interior; serine would be on the exterior of the globular protein.
Read the following sentences, and then choose one option below. I. "In this study, we tested the hypothesis that the cause of muscle mass loss after nerve damage is an increase in the protein TRB3." II. "In this study, we tested the hypothesis that treatment with an antibody that blocks the enzymatic activity of protein PAPP-A will reduce atherosclerotic plaque progression."
I is a hypothesis, but II is a prediction.
Read the following sentences, and then choose one option below. I. "We tested the hypothesis that the level of vitamin D in blood serum correlates to the expansion of endothelium-dependent blood vessels." II. "We tested the hypothesis that PINK1 and Parkin promote mitochondrial loss by producing targeted destruction of core proteins of mitochondrial development."
I is a prediction, but II is a hypothesis.
If a cell developed a mutation in its MAP2K1 gene (encodes MEK, protein kinase 2) that prevented MEK from being recognized by phosphatases, how would the HER2 enzyme-linked receptor signaling cascade and the cell's behavior change?
If the MAP2K1 mutation prevented MEK from being recognized by phosphatases, the HER2 enzyme-linked receptor signaling cascade would not be deactivated (as phosphatases take phosphates off of proteins in the phosphorylation cascade) and could cause the cell to become cancerous (as there would be no way to deactivate the signal transduction pathway). -not recognized by phosphatase, therefore phosphate cannot be removed and MEK cannot be deactivated -If MEK cannot be dephosphorylated, the signaling cascade downstream of MEK will continue since signal can't be turned off. -HER2 signaling cascade stimulates cell division. Therefore, the cell will continue to divide, possibly leading to tumor/cancer
Why can bacterial ribosomes begin translation before mRNA synthesis is completed, but eukaryotic ribosomes can't?
In prokaryotes, transcription and translation take place in the cytoplasm.
Coenzyme Q is often sold as a supplement w/ numerous benefits. What is one reasonable effect of CoQ supplementation?
Increase in ATP generation
A mutation that reduced the activity of the p53 gene would most likely:
Increase progress through cell cycle
Which of the following correctly matches a component of the cytoskeleton to one of its functions?
Intermediate filaments anchor the nucleus
Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because ________.
Intracellular receptors are present only in target cells
Which statement about quorum sensing is FALSE? Quorum sensing ________.
Is a type of cell-cell communication only in eukaryotes
Why is "wobble pairing" important in translation?
It allows 40 different tRNAs to translate all 61 codons.
What is the role of PEP carboxylase in C4 and CAM plants?
It fixes CO2 into an organic acid.
You have isolated a previously unstudied protein, identified its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites. One of these is large, apparently the binding site for the large substrate; the other site is small, possibly a binding site for a regulatory molecule. What do these findings tell you about the mechanism of this protein?
It is probably an enzyme that works through allosteric activation.
What can you infer about a high-molecular-weight protein that cannot be transported into the nucleus?
It lacks a nuclear localization signal (NLS)
Why might a point mutation in DNA make a difference in the level of a protein's activity?
It might substitute a different amino acid in the active site.
Which of the following would halt glycolysis:
Lack of ATP
Which of the following would halt glycolysis:
Lack of NAD+
What would be the consequence(s) for DNA synthesis if DNA ligase were defective?
Lagging strand synthesis would be incomplete; leading strand synthesis would be largely unaffected
R-group of serine is -CH2-OH. R group of leucine is -CH2-CH-(CH3)2. Where would you find them in a protein in water?
Leucine: interior // Serine: exterior
Which of the following macromolecules do NOT have polymers?
Lipids
LuxR is allosterically regulated by the signaling inducer molecule secreted by V. fischeri. What does this statement mean?
LuxR is regulated by a change in shape; only the shape with the inducer allows LuxR to bind a DNA regulatory sequence.
Which of the following would you expect of a eukaryote having telomerase RNA?
Maintenance of chromosome length in gametes
What are prions?
Misfolded versions of normal protein that can cause disease
Transmissible spongiform encephalopathies (TSEs), also known as prion diseases, are a diverse group of rare neurodegenerative disorders that include Creutzfeldt-Jakob disease in humans, bovine spongiform encephalopathy (mad cow disease) in cattle, scrapie in sheep, and chronic wasting disease in deer and elk. These disorders may arise spontaneously, by inheritance, or by way of infection. The spontaneous forms (not inherited genetically) are the most common and in humans spontaneous prion diseases account for approximately 85% of all cases. TSE diseases are caused by a change in shape of a cellular protein from its normal tertiary structure to a misfolded, aggregated form. A prion can convert a normal cellular protein (PrPc) into a prion, and thereby propagate an infection. The normal cellular protein, PrPc, is a copper-binding, cell membrane protein that is abundant in the central nervous system and peripheral nervous system. Aggregated prion proteins lead to massive degeneration of the brain, dementia, difficulty in movement, and eventual death. Prion diseases have thus revealed the frightening phenomenon of infectious neurodegenerative diseases. Fortunately, prion diseases acquired by infection are very rare, occurring in less than 1% of the cases. What are prions?
Misfolded, infectious proteins.
The graph below shows the rate of product formation in an enzyme-catalyzed reaction as a function of varying reactant (substrate) concentration, with the concentration of enzyme constant. In the figure above, why does the reaction rate plateau at higher reactant concentrations?
Most enzyme molecules are occupied by substrate at high reactant concentrations.
What scientific hypothesis can be tested by a pulse-chase experiment?
Movement of molecules within a cell over time
If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?
Nothing; the reaction will stay at equilibrium
The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?
Nuclease, DNA polymerase, DNA ligase
If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown in the accompanying figure? (diagram just showing the full citric acid cycle)
Oxaloacetate will accumulate, and citric acid will decrease (remember oxaloacetate is the last step that then combines with acetyl coA to restart the cycle, so if pyruvate oxidation is blocked, the cycle will not continue)
In mechanism, photophosphorylation is most similar to:
Oxidative phosphorylation in cellular respiration
Human papillomavirus can cause cervical cancer. The virus encodes E6, a protein that binds p53. Based on this fact, how would you describe the normal activity of p53 in a normal cell?
P53 is a gatekeeper for the G1 checkpoint
Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are ________.
Part of the extracellular matrix
Which of the following R-group interactions are NOT found in the tertiary structure of a protein?
Peptide bonds
This molecule accepts e- from the excited p680 reaction center of PS II in light-dependent reactions of photosynthesis
Pheophytin
In C4 & CAM photosynthesis, the 1st (& maybe most important) step involves fixation of CO2 to what high-energy molecule
Phosphoenolpyruvate
Gerstmann-Sträussler-Scheinker disease (GSS) is a rare inherited disease in humans associated with mutations in the PrPc protein gene that change amino acids within the protein, and make the GSS protein more prone to misfolding and aggregation. When researchers changed six histidines for tyrosines, PrPc lost its ability to bind copper. The structural formula of histidine and tyrosine are shown below. The R-groups highlighted in gray are______. (diagram showing amino acid structures- noteable: NH+ on histidine and OH on tyrosine)
Polar (partial charges can form with hydrogen bonds) for tyrosine and electrically charged/basic for histidine
Which of the following levels of gene expression allows the most rapid response to environmental change?
Post-Translational Control
Which of the following is most likely to block a second messenger system:
Preventing the exchange of GDP for GTP.
The image below shows a cell in a stage of mitosis. Which stage of mitosis is this and how many chromosomes are present? How many chromosomes will be present at the end of S-phase? (diagram showing 4 duplicated chromosomes)
Prophase; 4 chromosomes; 4 chromosomes
In eukaryotic gene expression, the step that most prokaryotes do not use is _____.
RNA processing
During transcription in a Eukaryote, an RNA Polymerase has reached a sequence in the DNA that is complementary to a stop codon: ATT. At this point what would happen?
RNA-pol II would transcribe the stop codon and continue transcribing until after the poly(A) signal, when RNA-pol II detaches from the DNA.
Within a cell, the amount of protein made using a given mRNA molecule depends partly on:
Rate at which mRNA is degraded
Why are polymerization reactions endergonic? Polymerization reactions ________.
Reduce entropy
Which process is most directly driven by light energy?
Removal of electrons from chlorophyll molecules
In general, a signal transmitted via phosphorylation of a series of proteins ________.
Results in a conformational change to each protein
The chemical reaction illustrated in the accompanying figure ________ (Picture showing two amino acids joining through dehydration synthesis)
Results in a peptide bond
A bacterium has a mutant tRNA with anticodon AAA (for codon UUU). The mutation does not allow amino acids to attach to the tRNA. Which of the following may happen in this cell? (think wobble base pairing)
Ribosomes could make proteins with phenylalanine if the mRNA included no UUU codons.
What organelles are part of the endomembrane system?
Rough ER, vesicles, golgi apparatus, plasma membrane
If the Rb protein was inactivated, which of the following would occur?
S phase would be activated in the absence of growth factors
All of the following are true for microtubules except: -Serve as tracks for motor proteins like myosin -Approximately 25 nm in diameter -Originate from the centrioles -Polymerization of microtubules is crucial for metaphase plate formation
Serve as tracks for motor proteins like myosin
Movement of the chromosomes during anaphase would be most affected by a drug that prevents ________.
Shortening of microtubules
Which of the following mutations would most likely have a harmful effect on an organism?
Single nucleotide insertion downstream of, and close to, start of coding sequence
DNA damage by environmental factors are often repaired by nucleotide excision repair enzymes. A research group studied the efficiency of these enzymes in naked mole rats and mice. It is a known fact that naked mole rats often live for 30 years (compared with mice who live about 3 years) and they also produce more telomerase than other rodents or humans. According to the data in the graph below, which of the following cannot be concluded about the relationship between lifespan of a species and DNA repair? (graph showing naked mole rats having a higher relative NER efficiency at every incubation time after UV radiation compared to mice)
Species with short life span recover from DNA damage faster than species with long life span.
The ATP made during fermentation is generated by ________.
Substrate-level phosphorylation
Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will most directly affect the ________.
Synthesis of ATP
A cell undergoing mitosis in a small mammal contains 16 chromosomes. During which phase of the cell cycle will this cell contain 32 chromosomes:
Telophase
Reactions that require CO2 take place in ________.
The Calvin cycle alone
Poliovirus is an RNA virus of the picornavirus group. At its 5' end, the RNA genome has a viral protein (VPg) instead of a 5' cap. This is followed by a nontranslated leader sequence and then a single long protein-coding region (~7000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acid analogues. Short-period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides. What conclusion is most consistent with the results of the radioactive labeling experiment?
The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.
Some cells, like skeletal muscle cells, have several nuclei per cell. Which of the following would be the best plausible explanation for this?
The cell underwent repeated mitosis, but cytokinesis did not occur
MPF in a cell that is going through the cell cycle is being expressed at half the normal amount. Which of the following is most likely?
The cell will be slower to transition from G2 to Mitosis.
Most CO2 from catabolism is released during:
The citric acid cycle
Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis?
The cyclin component of MPF is degraded
To pass the G1 checkpoint, all of the following would be expected to occur in a normal cell after exposure to growth factors EXCEPT ________.
The degradation of E2F
Recall from the "Mystery of the Newt" (Lectures 1 & 2) that a single newt killed three hunters after it got into their coffee pot. As the newt was boiled over the campfire, a substance on its skin—called tetrodotoxin (TTX)— contaminated the water to make a lethal brew. How did TTX kill the hunters? In the early 1960s, researchers determined that TTX interferes with the activity of nerve and muscle tissue by binding to a sodium ion channel in the plasma membranes of nerve cells. Research on the structure of voltage-gated sodium channels revealed that TTX binds to certain amino acid residues in the pore of the channel, interfering with its normal function. In the absence of functional voltage-gated sodium channels, signals between the brain and muscles are disrupted and the campers likely died of either respiratory or heart failure. After a sodium gradient is established, which side of the plasma membrane would you expect to be more positively charged?
The extracellular side of the membrane will be more positively charged.
Exposure to a chemical mutagen results in a change in the DNA sequence. The branch site A in Intron 1 is changed to a C. What affect, if any, might this have on transcription and the gene product formed? Use the model of a eukaryotic transcript below: (model w 3 exons w 2 introns (intron 1 and 2) in between
The gene would be transcribed, splicing would occur, and the protein formed will be shorter than normal.
Enzymes that readily break starch apart cannot hydrolyze the glycosidic linkages found in cellulose. Why is this logical?
The geometry of the bonds is different, and the shapes of enzyme active sites are highly specific.
Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?
The phosphodiester linkages of the polynucleotide backbone would be broken.
Recall from the "Mystery of the Newt" (Lectures 1 & 2) that a single newt killed three hunters after it got into their coffee pot. As the newt was boiled over the campfire, a substance on its skin—called tetrodotoxin (TTX)— contaminated the water to make a lethal brew. How did TTX kill the hunters? In the early 1960s, researchers determined that TTX interferes with the activity of nerve and muscle tissue by binding to a sodium ion channel in the plasma membranes of nerve cells. Research on the structure of voltage-gated sodium channels revealed that TTX binds to certain amino acid residues in the pore of the channel, interfering with its normal function. In the absence of functional voltage-gated sodium channels, signals between the brain and muscles are disrupted and the campers likely died of either respiratory or heart failure. The figure below shows the activated and deactivated conformations of the voltage-gated sodium channel. Changes in conformation are based on a regulatory alpha-helix (represented by the gray cylinder on each side of the channel) that slides closer to the cytoplasm in the deactivated state and closer to the exterior of the cell in the activated state. What type of amino acids would you expect to be included in the regulatory alpha helix based on its change in position? (remember video showing the alpha helices with a plus charge)
The helix would contain basic (positively charged) amino acids, such as lysine, arginine, and histidine.
Inhibitors of microtubule assembly, vinblastine for example, are used for cancer chemotherapy. How does an inhibitor of microtubule assembly affect cancerous cells?
The inhibitors restrict the separation of chromosomes, thereby stopping cell division.
In a photosynthetic eukaryote, a thylakoid membrane protein involved in electron transport is nonfunctional. It was discovered that a positively charged amino acid was replaced with a negatively charged amino acid. How might this change affect photosynthesis?
The light capturing reactions will stop functioning
Why are hydrocarbons insoluble in water?
The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.
Scientists exposed two species of differently pigmented sponges to a chemical that disrupted the cell-cell interaction, and the cells of the sponges dissociated. They then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. They found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species. How do you explain these results?
The molecules responsible for cell-cell adhesion differed between the two species of sponge
Compare the two cells shown in this image. Which of the following statements is correct? (diagram showing a cell going from 2 chromosomes to 2 duplicated chromosomes)
The number of chromosomes in both cells is the same, but the right cell contains twice the amount of DNA as the left cell.
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
The pH of the matrix increases
What is the difference between an aldose sugar and a ketone sugar?
The position of the carbonyl groups
Predict what would happen if the lac repressor were altered so it could not release lactose once lactose was bound to it.
The repressor could not bind DNA.
A student has drawn this model to study for her exam. Which statement is FALSE about her model? (model showing a cross-sectional, or side, view of a membrane)
The shape with the dark area represents a barrier to transport *(the dark area is actually a transport protein)
Which of the following is the first event to take place in translation in eukaryotes?
The small subunit of the ribosome recognizing and attaching to the 5' cap of mRNA
Scientists discovered that the enhancer associated with hair color has a binding site for a particular transcription factor. One of the binding sites has the sequence CACTAAG and is associated with dark hair, and the other form of the binding site has the nearly identical sequence CGCTAAG. How could these two nearly identical enhancer binding sites lead to different rates of initiating transcription of the regulated gene?
The transcription factor could bind with different affinities to the two closely related sequences, with the sequence promoting stronger binding leading to higher frequencies of transcription initiation.
Some bacteria are metabolically active in hot springs because
Their enzymes have high optimal temperatures
How do the α and β forms of glucose differ?
Their ring structures differ in the location of a hydroxyl group
Why are the genes involved in lactose metabolism in E. coli considered to be an operon?
They are all controlled by the same promoter.
What would happen to blood cells in a hypertonic solution?
They would shrivel up
Which statement is TRUE for the model shown here: (picture showing a nucleotide w/ a sugar with a 2' hydroxyl)
This is a monomer of RNA (ribose)
In a Eukaryotic Gene "X", a mutation changes the first AUG (for Methionine) in the mRNA to AUA. Of the following, which would be more likely to happen in this cell?
Translation would begin at the second AUG, if there is a second AUG. The protein would be shorter.
In a ribosome, a mutation has changed a nucleotide in the ribosome's active site. The ribozyme cannot cause the formation of a covalent bond. Which of the following might be a reasonable explanation of how this might affect translation?
Translation would continue, producing a series of free amino acids, all unattached because the ribozyme is unable to form peptide bonds.
Predict the effect of removing the 5' cap from eukaryotic mRNA.
Translation would not occur because the ribosome would not be able to bind to the mRNA.
Aquaporins are proteins that control the passage of water molecules across a cell membrane. The protein forms a pore, or opening, in the membrane. You isolate what you think are two different molecules of aquaporin, and determine that one of the proteins has a larger pore diameter than the second. Which of the following do you conclude?
Two forms of aquaporins will have different sequences of amino acids
In a pulse chase experiment, radioactively labeled amino acids are fed to a culture of bacteria and then the bacteria are added to a culture of macrophages (white blood cells). From earliest to latest, where would radioactive materials appear?
Vesicles near cell surface, vesicles deeper in cell, lysosomes, cytoplasm
In a 'pulse-chase' experiment, radioactively labeled amino acids are fed to a culture of bacteria, and then the bacteria are added to a culture of macrophages (white blood cells). From earliest to latest, where would radioactive materials appear?
Vesicles near the cell surface, vesicles deeper in the cell, lysosomes, cytoplasm.
The light-producing genes of V. fischeri are organized in an operon that is under positive control by an activator protein called LuxR. When would you expect the genes of this operon to be transcribed?
When LuxR is bound to a DNA regulatory sequence.
Predict what mode of transmission is most likely to account for the following pedigree: gen 1: affected female-unaffected male gen 2: unaffected male-unaffected female (1), affected male, unaffected female, affected male-affected female (2) gen 3: (1 children) affected male, unaffected female, unaffected male, unaffected female (2 children) affected male, affected female, affected male
X-linked recessive
What is responsible for termination of transcription in eukaryotic protein-coding genes?
a polyadenylation, or poly(A), signal
You eat a large plate of no-fat pasta for a late evening snack. Using your knowledge of cellular respiration and Figure 9.3 as a reference, indicate whether (1) it is possible for the carbon atoms contained in the pasta to end up in the indicated molecules and (2) how it is possible or why it is not possible. -Glycogen in muscle tissue: Possible? If so, how? If not, why? -Cellulose comprising the cell wall in your muscle tissue: Possible? If so, how? If not, why? -A ligand that binds to an intracellular receptor: Possible? If so, how? If not, why? -The DNA that codes for an intracellular receptor:Possible?If so, how? If not, why? -The intracellular receptor itself:Possible?If so, how? If not, why? -The CO2 you exhale:Possible?If so, how? If not, why? -The water you exhale: Possible? If so, how? If not, why?
Yes; extra glucose monomers are polymerized into glycogen and stored in muscle and liver. No; humans have no cellulose or cell walls. Yes; pyruvate oxidation gives rise to Acetyl CoA which is used for fatty acid synthesis and therefore lipid synthesis. The signal for an intracellular receptor is a lipid. Yes; intermediates of glycolysis are used for nucleotide synthesis which are monomers for DNA. Yes; intermediates of the citric acid cycle are used for amino acid synthesis which are monomers for proteins. An intracellular receptor is a protein. Yes; the carbons in the pasta are in the form of starch, a carbohydrate, which is broken down into glucose monomers. Glucose is oxidized during glycolysis and the Krebs cycle and released as CO 2. No; water does not contain carbon.
You want to engineer a eukaryotic gene into a bacterial cell and have it expressed. What must be included in addition to the coding exons of the gene?
a bacterial promoter sequence
A mutation has changed a sequence in an exon in DNA. The normal mRNA was: AAACCCUAU. After the mutation, the sequence is: AAAUCCCUAU. What would be the effect of this mutation? (you will be given the mRNA codon table for this)
a change in multiple amino acids of the protein, from Lys-Pro-Tyr... to Lys-Ser-Leu...
If any of the following hypothetical drugs could be developed, which would be the most effective in preventing cholera?
a drug that blocked the DNA-binding activity of the ToxR activator.
G proteins are activated when _____.
a hormone binds to the receptor that they are attached to
A series of enzymes catalyze the reaction X → Y → Z → A . Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. Using this information, substance A functions as a ____________ and substance X functions as a ____________.
allosteric inhibitor; substrate -this is feedback inhibition
A ribozyme is ________.
an RNA with catalytic activity
RNases and proteases are enzymes that destroy RNAs and proteins, respectively. In order to prevent recognition of pre-mRNA regions critical for splicing, ________ should be added to a spliceosome.
an RNase specific for snRNAs
ATP can be synthesized by substrate-level phosphorylation, oxidative phosphorylation, and photophosphorylation. Oxidative phosphorylation is an example of ________.
an endergonic reaction coupled to an exergonic reaction
David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). These two regions of the promoter _____.
bind the sigma subunit that is associated with RNA polymerase
How might a change of one amino acid at a site, distant from the active site of an enzyme, alter an enzyme's substrate specificity?
by changing the shape of an enzyme
Which of the following is an example of potential energy rather than kinetic energy? a. The muscle contractions of a person mowing grass b. Water rushing over Niagara Falls c. A molecule of glucose d. A crawling cockroach foraging for food
c. A molecule of glucose
Glycosidic linkages are common to ____________, whereas __________ are found in fats (triglycerides).
carbohydrates; ester linkages
A researcher hypothesizes that plant leaf cells express fewer genes in the middle of the night compared to right before the sun rises. She tests her hypothesis by introducing DNase into the cells at both times. She finds that DNA is cut much more right before the sun rises and that more mRNA is present in the cells at that time. The best interpretation of these results is that _____.
chromatin regulation is a crucial component of plant gene regulation overnight
Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and can be assayed to track their incorporation. In a pulse—chase experiment, a student—faculty research team introduced labeled thymine (T) nucleotides into a culture of non-dividing human cells. After a short time, they added large amounts of unlabeled T nucleotides. Which cell cycle phase would contain labeled T nucleotides incorporated into the DNA? a. G1 b. S, G2, and M only c. S d. None
d. None
Eukaryotic genomes have gene sequences that can code for more than one polypeptide sequence because _____.
different introns can be cut out of the pre-mRNA
The pedigree below was created for race horses in an attempt to eliminate individuals susceptible to hyperkalemic periodic paralysis (HYPP). Circles represent females; squares represent males. Full symbols represent affected individuals. What type of disease is this? (pedigree with an affected individual in every generation, and gender does not play a factor in the disease)
dominant autosomal
Chondrocytes are cells found in the cartilage in our joints. In some forms of osteoarthritis, destruction of the chondrocyte extracellular matrix is associated with a diseased endoplasmic reticulum. This finding supports the idea that _____.
endoplasmic reticulum is involved in the synthesis of extracellular matrix
The bacterium Bacillus anthracis, commonly known as anthrax, causes an often fatal disease that is also called anthrax. The U.S. Centers for Disease Control and Prevention (CDC) recommends that anyone who might have been exposed to anthrax begin treatment with the antibiotic ciprofloxacin, a DNA-synthesis inhibitor. For ciprofloxacin to be useful, it must work
exclusively against bacterial DNA synthesis proteins
Order the following molecules/ions based on increasing rate of transport
free ions < large polar < small polar < small nonpolar
Consider the HIV enzyme called protease. The amino acid residues at the active site are highly hydrophobic. In designing a drug that would bind to the active site and jam it, researchers should use a molecule that is ______.
hydrophobic
Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses?
in or near the active site
In a normal cellular protein, where would you expect to find a hydrophobic amino acid like valine?
in the interior of the folded protein, away from water
Which of the following, when taken up by a cell, binds to a repressor so that the repressor no longer binds to the operator?
inducer
Recall from the "Mystery of the Newt" that a single rough-skinned newt killed three hunters after it got into their coffee pot. As the newt was boiled over the campfire, a substance on its skin called tetrodotoxin (TTX) contaminated the water to make a lethal brew. The newts store TTX in secretory vesicles inside gland cells, and secrete the toxin as a defense mechanism. When newts are stimulated to secrete TTX, predict what type of microtubule motor would be used to transport the secretory vesicles to the plasma membrane.
kinesin
During eukaryotic translation, which of the following is used?
mRNA
What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3' (you will be given an mRNA codon table for this)
met-ser-ser-leu-ser-leu
Point mutations are referred to as missense, silent, frameshift, or nonsense when they change the protein-coding potential of a gene. What is another group of mutations that may have important consequences for gene expression?
mutations that exist outside coding sequences in regulatory regions
Rats that are the offspring of parents that were raised with poor nutrition have a greater chance of developing disorders similar to type 2 diabetes, regardless of the alleles they inherit. This shows that _____.
patterns of gene expression may be inherited
Prions are unusually resistant to an enzyme called proteinase K which breaks proteins into their monomer building blocks. Which bonds are being broken?
peptide bonds between amino acids
Which of the following molecules contains at LEAST one peptide bond?
peptidoglycan
Which of the following is not dependent upon hydrogen bonding interactions?
primary structure of a protein
Eukaryotes have three nuclear RNA polymerases. The primary function of RNA polymerase II is transcription of ________.
protein-coding genes
What is the oxidizing agent in the following reaction: Pyruvate + NADH + H+ -> lactate + NAD+ (oxidizing agent is the one reduced)
pyruvate
Pancreatic cells export many digestive enzymes. Of the following organelles, which would you expect to be in abundance in these cells?
secretory vesicles
Mendel's principle of segregation reflects what event in meiosis?
separation of homologous chromosomes at meiosis I
(epigenetics research box of rat mothers fed a low protein diet) In the follow-up work to the experiment shown in Figure 19.6, the researchers used a technique that allowed them to see if two DNA sequences are in close physical proximity (association). They applied this method to examine how often an enhancer and the core promoter of the Hnf4a regulatory gene were near each other. A logical prediction is that compared with rats born to mothers fed a healthy diet, the Hnf4a gene in rats born to mothers fed a protein-poor diet would
show a lower frequency of promoter-enhancer association.
In E. coli, if RNA polymerase is missing ________, then transcription initiation would not occur at the appropriate initiation sites.
sigma
An atom has three electrons in its valence shell. What types of covalent bonds is it capable of forming?
single, double, or triple
Cell walls are used by many different organisms for protection from their environment and structural support. These cell walls must be insoluble in water; otherwise, they would dissolve the first time an organism got wet. Which of the following carbohydrates would you expect to be most soluble in water?
starch
Insulin is a peptide hormone produced by the pancreas. Even though it circulates throughout the bloodstream, it affects only certain cells and tissue. This data would suggest that _____.
target specificity is determined at the level of a receptor molecule on the surface of the cell
The rate of enzymatic activity can be controlled by _____ while the function can generally be governed by _____.
temperature; allosteric molecules
One general common characteristic of the most serious cancers might be _____.
the ability of defective cells to relocate to other tissues
A solution of starch at room temperature does NOT readily decompose to form a solution of simple sugars because __________ .
the activation energy barrier for this reaction cannot easily be surmounted at room temperature
What ensures that the correct amino acid is added during translation?
the anticodon of a properly formed aminoacyl tRNA
Scientists discovered that the difference between blond and dark hair in humans and other mammals comes down in part to a single nucleotide difference in the DNA sequence of an enhancer that lies more than 350,000 base pairs upstream from the coding region of the gene it controls. On average, blonds transcribe this gene less efficiently than people with dark hair. Which of the following statements about this blond/dark hair enhancer is correct?
the enhancer is associated with a protein during transcription initiation.
Muscle contraction is initiated when a section of a DHPR protein moves, allowing calcium ions to flow into a cell. The protein is said to act as a gate for calcium ions. This is an example of ___________.
the flexible nature of proteins
The Hawaiian bobtail squid is able to glow from luminescent Vibrio fischeri bacteria held in its light organs. As it swims at night near the ocean surface, it adjusts the amount of light visible to predators below to match the light from the stars and moon. Predators have a hard time seeing the illuminated squid against the night sky. The bacteria glow in response to a molecule that regulates expression of genes involved in light-producing chemical reactions. The regulator controls production of the genes' mRNA. Therefore, the light-producing genes are under____.
transcriptional control
Sodium ion is __________ to cross a pure phospholipid bilayer because it is __________ .
unable; charged
To determine the fate of O2 in cellular respiration, mice were allowed to inhale radioactive O2. The first molecules to acquire radioactivity in their cells were _____.
water
Eating even a single death cap mushroom (Amanita phalloides) can be fatal due to a compound called α-amanitin, a toxin that inhibits transcription. α-Amanitin inhibits transcription by binding inside an RNA polymerase to a region other than the active site that catalyzes addition of a nucleotide to the RNA chain. Based on the figure below, which of the following could be a reasonable prediction of how the toxin might function to inhibit transcription? (diagram showing prokaryotic transcription, with site C in the promoter, site A in sigma, site B in the DNA strand, and site D in the RNA polymerase)
α-Amanitin binds to site D to inhibit transcription.