Cell Biology Exam 1

during DNA replication, the single stranded DNA binding protein (SSB)

prevent the folding of a single stranded DNA

Sorry the following events in a sequence that would lead to long-term potentiation (LTP).

(B) Glutamate release into the synaptic clefts (A) Activation of AMPA receptors (D) Postsynaptic membrane depolarization (E) Activation of NMDA receptors

Neuromuscular transmission involves the sequential activation of several ion channels.

(E) Opening of voltage-gated Ca2+ channels in the motor neuron (C) Opening of inotropic acetylcholine receptors on the muscle cell plasm membrane (A) Opening of voltage-gated Na+ channels in the muscle cell plasma membrane (D) Opening of voltage-gated Ca2+ channels in the T tubules (B) Opening of Ca2+ release channels in the sarcoplamic reticulum membrane

Dopamine is a neurotransmitter involved in the reward pathways in the brain, and it's decreased activity has been associated with diseases such as Parkinson's disease and attention deficit/hyperactivity. Which of the following drugs is NOT a likely candidate to treat these diseases?

Chlorpromazine, a dopamine antagonist that binds to an inhibits dopamine receptors

Which of the following is directed by transcription activators in eukaryotic cells in order to provide a more accessible DNA for the transcription machinery? A) Nucleosome remodeling B) Histone removal C) Histone modifications D) All of the above

D) All of the above

Imagine conducting an experiment in which you add a non-hydrolyzable analog of GTP (i.e. a form of GTP that cannot be cleaved to GDP) to a culture of cells. Where do you think the protein Ran would localize under these conditions? A) The nucleolus B) Mitochondria C) Lysosome D) Cytoplasm E) Nucleus

D) Cytoplasm

The polarity in a DNA strand is indicated by referring to one end as the 3' end and the other as the 5' end. Which structure is on the 3' end? A) Hydrogen atom B) Phosphate group C) Nitrogenous base D) Hydroxyl group E) Carboxyl group

D) Hydroxyl group

Which of the following better represents the process of adaptation mediated by the voltage-gated Ca2+ channels and Ca2+ - activated K+ channels? The vertical axis, while he horizontal axis is the time of constant stimulation (in milliseconds)

D) Three peaks. Two similar and one wide

Genes that are always "turned on" in a cell are referred to as A) regulated genes. B) mutations. C) inducible. D) constitutive. E) catabolic.

D) constitutive.

11. Which of the following lipids do you expect to be a canonical scramblase substrate in the plasma membrane? A. Ganglioside GM1 B. Cholesterol C. Glycosylphosphatidylinositol D. Phosphatidylethanolamine E. Galactocerebroside

D. Phosphatidylethanolamine

For which of the following ions is the intracellular concentration typically higher than the extracellular concentration? A. Sodium B. Calcium C. Magnesium D. Potassium E. Chloride

D. Potassium

Which of the following molecules can be considered a final product in the flow of information within a cell? A) DNA B) RNA C) protein D) lipid E) Protein or RNA can be the final product of a gene

E) Protein or RNA can be the final product of a gene

This large and complex general transcription factor has a DNA helicase activity that exposes the template for RNA PolII transcription. It also has a kinase activity that phosphorylates the C-terminal domain of the polymerase on Ser5 leading to promoter clearance. It is... A) TFIIB B) TFIID C) TFIIE D) TFIIF E) TFIIH

E) TFIIH

A certain neuron is a mouse brain is firing about 300 times per second, whereas almost all of its neighboring neurons are firing at much lower rates of only a few times per second. This implies that...

It is probably of a different type compared to most of its neighbors

Which of the following transporters is NOT electrogenic?

Na+- independent CI-HCO3- exchanger

The inactivation rate of voltage-gated Na+ and K+ channels can regulate the firing frequency of neurons. Which of the following combinations results in the highest firing frequency?

Rapid inactivation of both Na+ and K+ channels

The level of cyclic AMP in E. coli cells grown in the presence of glucose and lactose will be:

much lower than the level in E. coli grown in lactose alone

Which of the following is correct regarding the electrical properties of cellular membranes?

none of the above

the genetic code is degenerate because

one particular amino acids can be encoded by more than one codon

Allolactose inactivates lac repressor

True

Each nucleosome contains

a histone octamer composed of two copies of" H2A, H2B, H3 and H4

how do eukaryotic transcription factors exert their effects on transcription when their binding sites can be thousands of base pairs away from the promoter?

the DNA between the bound site and the polymerase-promoter complex loop out, increasing proxomity

each replication fork requires both leading and lagging strand synthesis because

the DNA templates are antiparallel and yet DNA polymerase can only work in one direction 5-3'

what is not a way chromatin remodeling complexes affect nucleosomes?

they can modify the n-terminal tails of histones (this is done by histone enzymes-cousin)

what is not a characteristic of a riboswitch?

they exert gene expression control only at the level of translation

what is the function of RNA dependent RNA polymerases in RNA interference?

they produce additional copies of the siRNA to ensure that the RNAi response is sustained and spread

Which of the following transporters mediates primary active transport when transporting the solutes in the directions indicated? The concentration of both solutes (shown as small circles and squares) is higher outside of the cell?

Small circle and the square are going outside

which of the following transcription factors is utilized by all three eukaryotic RNA polymerases to initiate transcription?

TBP (TATA box binding protein)

the nuclear DNA polymerases in human cells

are unable to initiate polymerization de novo (in the absence of a primer)

Tryptophan inactivates trp repressor

False

which of the following motifs found in transcriptional regulatory proteins is thought to interact with DNA only through the minor groove?

homeodomain

which of the following repair pathways can accurately repair a double strand break?

homologous recombination

23. In intestinal epithelial cells, the different plasma membrane domains are separated from each other by special barriers. ( ) These barriers are set up by nanoscale lipid raft domains. ( ) Proteins normally cannot pass through these barriers, whereas any membrane lipid can do so freely. ( ) The asymmetric distribution of membrane proteins resulting from these barriers is functionally important. ( ) These barriers are a result of proteins of the apical surface forming a large aggregate together that excludes proteins of the other domains.

(F) These barriers are set up by nanoscale lipid raft domains. (F) Proteins normally cannot pass through these barriers, whereas any membrane lipid can do so freely. (T) The asymmetric distribution of membrane proteins resulting from these barriers is functionally important. (F) These barriers are a result of proteins of the apical surface forming a large aggregate together that excludes proteins of the other domains.

Indicated true (T) and false (F) statements below regarding ion channels in cellular membranes. Your answer would be a four-letterr string go composed of letter

(T) With patch-clamp recordings, it is possible to study ion transport through single molecule of a channel protein. (F) Cells that are not electrically excitable often lack gated ion channels in their plasma membrane (F) The aggregate current crossing a patch of plasma membrane represents the degree to which each individual channel is open at that time (F) Patch-clamp recordings have shown that any voltage-gated ion channel opens as soon as the membrane potential is altered

The Nernst equilibrium potential for an ion that is 10 times more concentred in the cytosol compared to the extracellular fluid is about -60 mV. How much would the potential be if the extracellular concentration decreases 100-fold with no changes in the intracellular concentration?

-180 mV

What would the predicted result be if Griffith injected mice with a mixture of heat-killed R bacteria and living S bacteria? 1) All mice would die. 2) All mice would die, but only if DNAse was added to the mixture prior to injection. 3) All mice would live, but only if DNAse was added to the mixture prior to injection. 4) All mice would live.

1) All mice would die.

Of what significance to Avery and his colleagues was the finding (made in 1932 by J. L. Alloway) that the same kind of transformation of R cells into S cells that Griffith observed to occur in mice could also be demonstrated in culture with isolated pneumococcus cells? 1) It made their experiment possible, because it allowed them to assay various fractions of S cells for transforming activity in culture. 2) It allowed them to analyze various fractions of S cells before their transformation into R cells to find out whether they demonstrate activity in culture. 3) It made their experiment possible, because it allowed them to assay various fractions of R cells for transforming activity in culture. 4) It allowed them to analyze various fractions of R cells before their transformation into S cells to find out whether they demonstrate activity in culture.

1) It made their experiment possible, because it allowed them to assay various fractions of S cells for transforming activity in culture.

If nucleoli are irradiated with a microbeam of ultraviolet light, synthesis of ribosomal RNA is inhibited. 1) Nucleoli are probably responsible for rRNA synthesis. 2) Ultraviolet light probably accelerates processes that prevent rRNA synthesis. 3) Ultraviolet light destroys all RNA molecules.

1) Nucleoli are probably responsible for rRNA synthesis.

Colloidal gold particles with a diameter of 5.5 nm equilibrate rapidly between the nucleus and cytoplasm when injected into an amoeba, but gold particles with a diameter of 15 nm do not. 1) The aqueous channels in nuclear pore complexes have diameters of at least 5.5 nm, but not as great as 15 nm. 2) Large gold particles have a larger charge which prevents them from passing through polar membrane. 3) Large gold particles are very slow and unwieldy, preventing them from passing through polar membranes 4) The aqueous channels in nuclear pore complexes have diameters of about 15-20 nm, but only particles with a diameter of one third could pass through them.

1) The aqueous channels in nuclear pore complexes have diameters of at least 5.5 nm, but not as great as 15 nm.

An exon within a coding region of a gene contains the following sequence: 5';-ATTGCACCTG-3'. Exposure of cells to a mutagen results in this sequence changing to 5'-ATTCGCACCTG-3'. Which of the following is true? 1) This gene has experienced a frameshift. 2) This gene has experienced a deletion. 3) This gene has experienced a double mutation. 4) This gene is now considered wild-type.

1) This gene has experienced a frameshift.

Sucrose crosses the nuclear envelope so rapidly that its rate of movement cannot be accurately measured. Sucrose crosses the nuclear envelope so rapidly that its rate of movement cannot be accurately measured. 1) Unlike most membranes, the nuclear envelope appears to be freely permeable to a polar organic molecule. 2) Sucrose can dissolve the nuclear envelope because of its polarity. After sucrose molecules have passed, nuclear envelope goes back to its initial state. 3) There is a small concentration difference between two sides of the nuclear envelope that forces sucrose to move very fast. 4) The nuclear envelope has pores that are designed to transport sucrose molecules so that they can cross it without any resistance.

1) Unlike most membranes, the nuclear envelope appears to be freely permeable to a polar organic molecule.

You are using genetic engineering to design a protein that needs to be synthesized in the cytoplasm and then localized in the nucleus of the cell. To accomplish this, you could add 1) a DNA sequence for a nuclear localization signal into the DNA that will be present in the mature protein. 2) the protein during mitosis, at a time when the nuclear membrane is dispersed. 3) a nucleotide or few nucleotides to the DNA sequence for the protein. 4) a series of specific polysaccharides to the carboxyterminal end of the protein. 5) inverted repeats to the DNA sequence for the protein.

1) a DNA sequence for a nuclear localization signal into the DNA that will be present in the mature protein

Enzymes that add ubiquitin to proteins have been found in the nucleus of eukaryotic cells. These enzymes would be most likely to regulate gene expression by __________. 1) causing degradation of transcription factors and changing which genes are expressed 2) causing activation of enhancer-binding proteins 3) causing a change in which introns are removed and changing the mature mRNA 4) causing degradation of histones and changing chromatin structure

1) causing degradation of transcription factors and changing which genes are expressed

Spontaneous hydrolysis reactions between DNA and surrounding water molecules commonly cause 1) depurination. 2) pyrimidine dimer formation. 3) tautomeric shift. 4) deletion mutations. 5) double-stranded DNA breaks.

1) depurination

In an experiment like that of the 1952 Hershey and Chase experiments, 35S was added to a phage replicating within its bacterial host. The new phage particles were carefully isolated and used to infect fresh bacterial cells in the absence of any radioisotopes. Where would you expect to find the 35S radioisotope immediately after infection? 1) in the phage ghosts outside the bacterial cells 2) incorporated into the bacterial cell wall 3) incorporated into the bacterial DNA 4) inside the bacterial cells, but separate from the bacterial DNA 5) inside the bacterial cells, but separate from the bacterial proteins

1) in the phage ghosts outside the bacterial cells

Which of the following types of RNA in eukaryotic cells come(s) from precursors that are subject to RNA processing? 1) rRNA, tRNA, and mRNA 2) rRNA and tRNA 3) tRNA and mRNA 4) mRNA

1) rRNA, tRNA, and mRNA

Beginning within the nucleus, the first step leading to the synthesis of a polypeptide is _____. 1) transferring of information from DNA to messenger RNA 2) translation of a DNA nucleotide sequence into a sequence of amino acids 3) translation of an RNA nucleotide sequence into a sequence of amino acids 4) linking of nucleotides to form a polypeptide 5) removal of introns from RNA and the stitching together of exons

1) transferring of information from DNA to messenger RNA

The permeability of a protein-free lipid bilayer to various molecules depends on their properties. Sort the following in order low to high permeability from left to right.

1. RNA oligonucleotide 2. ATP 3. Na+ 4. Glucose 5. Urea

Voltage-gated cation channels in the plasma membrane of a neuron open when the membrane potential passes a threshold value that is about 20 mV above the resting potential.

18 pN, toward the cell exterior

For a double-stranded DNA molecule in which 40% of the bases are either G or C, what can you conclude about its content of the base A? 1) 20% of the bases must be A. 2) 30% of the bases must be A. 3) 40% of the bases must be A. 4) 60% of the bases must be A. 5) It is impossible to determine.

2) 30% of the bases must be A.

You analyze a DNA sample and find that its base composition is 30% A, 20% T, 30% G, and 20% C. What can you conclude about the structure of this DNA? 1) Because A is half as much again as T, and G is half as much again as C, this must be a mutated double-stranded DNA molecule. 2) Because A does not equal T, and G does not equal C, this cannot be a double-stranded DNA molecule. It must therefore be a single-stranded DNA. 3) Because A equals G, and T equals C, this must be a double-stranded DNA molecule. 4) There is not enough information to determine whether it is a single-stranded or a double-stranded DNA molecule.

2) Because A does not equal T, and G does not equal C, this cannot be a double-stranded DNA molecule. It must therefore be a single-stranded DNA.

If a DNA-binding protein "reads" a short stretch of DNA and detects the following "second" genetic code provided by the functional groups located on each base as H-HD-CH3-HA-HA-HA-HA-HD, then what is the corresponding sequence of bases? 1) C-T-A-G 2) C-T-G-A 3) C-G-G-A 4) C-A-G-A

2) C-T-G-A

DNA replication is 1) conservative. 2) semiconservative. 3) irregular. 4) dispersive. 5) None of these selections apply.

2) Semiconservative

Which statement about the polarity of DNA strands is true? 1) The 5' end has a free OH group. 2) The 3' end has a free OH group. 3) The 3' end has a free phosphate group.

2) The 3' end has a free OH group.

If gold particles up to 26 nm in diameter are coated with a polypeptide containing a nuclear localization signal (NLS) and are then injected into the cytoplasm of a living cell, they are transported into the nucleus. If they are injected into the nucleus, however, they remain there. 1) The NLS only triggers transport from nucleus to cytoplasm, not from cytoplasm to nucleus, suggesting that NLS receptor proteins (importins) function only in the nucleus. 2) The NLS only triggers transport from cytoplasm to nucleus, not from nucleus to cytoplasm, suggesting that NLS receptor proteins (importins) function only in the cytoplasm. 3) The NLS only triggers transport from cytoplasm to nucleus, not from nucleus to cytoplasm, suggesting that gold particles have a large charge that prevents their moving away from nucleus. 4) The NLS only triggers transport from cytoplasm to nucleus, not from nucleus to cytoplasm, suggesting that NLS receptor proteins (importins) are attached to the outer side of the nucleus.

2) The NLS only triggers transport from cytoplasm to nucleus, not from nucleus to cytoplasm, suggesting that NLS receptor proteins (importins) function only in the cytoplasm.

Treatment of nuclei with the nonionic detergent Triton X-100 dissolves the nuclear envelope but leaves an otherwise intact nucleus. 1) The nucleus seems to produce a new insoluble envelope following the dissolution of the previous one. 2) The integrity of the nucleus does not seem to depend entirely on the envelope. 3) While dissolving the nuclear envelope, Triton X-100 produces a new envelope that protects the nucleus

2) The integrity of the nucleus does not seem to depend entirely on the envelope.

How is it possible that DNA from smooth streptococcal cells results in synthesis of a polysaccharide capsule? 1) The order of nucleotides in DNA specifies the order of sugar subunits in the polysaccharide. 2) The order of nucleotides in DNA specifies the order of nucleotides in RNA, which in turn specifies the order of sugar subunits in the polysaccharide. 3) The DNA provides the sugars (deoxyribose) used in the synthesis of the polysaccharide. 4)The order of nucleotides in DNA specifies the order of amino acids in the enzymes needed to synthesize the polysaccharide.

2) The order of nucleotides in DNA specifies the order of amino acids in the enzymes needed to synthesize the polysaccharide.

Nuclear pore complexes sometimes stain heavily for RNA and protein. 1) The stained pores contain complexes of RNA and protein, probably ribonucleo-protein particles attached to the membrane by hydrogen bonds. 2) The stained pores contain complexes of RNA and protein, probably ribonucleo-protein particles caught in transit. 3) The stained pores contain complexes of RNA and protein, probably ribonucleo-protein particles that are part of the nuclear pore complex.

2) The stained pores contain complexes of RNA and protein, probably ribonucleo-protein particles caught in transit.

The minor groove contains less information about the identity of base pairs than the major groove because of the 1) geometry of base pairing and structure of ribose. 2) glycosidic bond angles and structure of pyrimidine bases. 3) glycosidic bond angles and geometry of base pairings. 4) glycosidic bond angles and structure of purine bases.

2) glycosidic bond angles and structure of pyrimidine bases

Which of the following organelles does not receive proteins by posttranslational import of proteins synthesized on cytoplasmic ribosomes? 1) nucleus 2) lysosome 3) chloroplast 4) peroxisomes 5) mitochondria

2) lysosome

If the gene encoding the lac repressor is mutated so that the repressor can no longer bind the operator, will a high level of transcription of that operon occur? 1) no, because cAMP levels are low when the repressor is nonfunctional 2) yes, because RNA polymerase will be able to bind the promoter and transcribe the operon 3) no, because RNA polymerase is needed to transcribe the genes 4) yes, but only when lactose is present

2) yes, because RNA polymerase will be able to bind the promoter and transcribe the operon

To help achieve proper base pairing and hence form a double helix, which condition must be met? 1) A pyrimidine base must pair with pyrimidine base. 2) A purine base must pair with a purine base. 3) A purine base must pair with a pyrimidine base.

3) A purine base must pair with a pyrimidine base.

How did the findings of Hershey and Chase help explain an earlier report (by T. F. Anderson and R. M. Herriott) that bacteriophage T2 loses its ability to reproduce when it is burst open osmotically by suspending the viral particles in distilled water before adding them to a bacterial culture? 1) By showing that a virus was indeed like a little hypodermic needle capable of injecting its nucleic acid into the cell, Hershey and Chase were able to explain Anderson and Herriott's observation in terms of an osmotic shock that causes the viruses to become more infective. 2) By showing that a virus was indeed like a little hypodermic needle capable of injecting its nucleic acid into the cell, Hershey and Chase were able to explain Anderson and Herriott's observation in terms of an osmotic shock that causes the viruses to better protect its nucleic acid. 3) By showing that a virus was indeed like a little hypodermic needle capable of injecting its nucleic acid into the cell, Hershey and Chase were able to explain Anderson and Herriott's observation in terms of an osmotic shock that causes the viruses to empty their nucleic acid contents into the medium.

3) By showing that a virus was indeed like a little hypodermic needle capable of injecting its nucleic acid into the cell, Hershey and Chase were able to explain Anderson and Herriott's observation in terms of an osmotic shock that causes the viruses to empty their nucleic acid contents into the medium.

A researcher wishes to increase the half-life of a particular mRNA that she is transfecting into a eukaryotic cell line. How should this researcher accomplish this goal? 1) Inhibit RNA polymerase I. 2) Inhibit the spliceosomes in the cell. 3) Increase the length of the poly(A) tail of the mRNA prior to transfection. 4) Increase the length of the 5'; cap of the mRNA prior to transfection.

3) Increase the length of the poly(A) tail of the mRNA prior to transfection.

A researcher exposes a bacterial culture to UV radiation and then subjects it to progressively higher temperatures. As the temperature increases, the bacteria have a progressively harder time surviving. Analysis of the dead bacteria reveals large amounts of misfolded, aggregated proteins compared to wild-type control bacteria exposed to the same temperature increase. Which of the following is a plausible explanation for the data? 1) DNA polymerase is mutated and nonfunctional. 2) The ribosomes are mutated and are nonfunctional. 3) Molecular chaperones have been mutated. 4) The initiator tRNA (fMet) has been mutated and is nonfunctional.

3) Molecular chaperones have been mutated.

Which of the following would be a reasonable experimental strategy to prevent translation of a particular prokaryotic mRNA without targeting the ribosome? 1) Inhibit the sigma factor. 2) Add suppressor tRNA molecules to the cell. 3) Mutate or remove the Shine-Dalgarno sequence on the mRNA. 4) Inhibit termination factors.

3) Mutate or remove the Shine-Dalgarno sequence on the mRNA.

Ribosomal proteins are synthesized in the cytoplasm but are packaged with rRNA into ribosomal subunits in the nucleus. 1) Ribosomal proteins must pass inward from the cytoplasm to the nucleus at a rate adequate to prevent proteins from dissolving; ribosomal subunits must move outward from the nucleus to the cytoplasm at a rate commensurate with their rate of dissolving. 2) Ribosomal proteins must pass outward from the nucleus to the cytoplasm to the nucleus at a rate adequate to sustain ribosomal subunit assembly; ribosomal subunits must move inward from the cytoplasm to the cytoplasm at a rate commensurate with their rate of assembly. 3) Ribosomal proteins must pass inward from the cytoplasm to the nucleus at a rate adequate to sustain ribosomal subunit assembly; ribosomal subunits must move outward from the nucleus to the cytoplasm at a rate commensurate with their rate of assembly.

3) Ribosomal proteins must pass inward from the cytoplasm to the nucleus at a rate adequate to sustain ribosomal subunit assembly; ribosomal subunits must move outward from the nucleus to the cytoplasm at a rate commensurate with their rate of assembly.

Of what significance to Watson and Crick were the data of their colleagues at Cambridge suggesting that the particular forms in which A, G, C, and T exist at physiologic pH permit the formation of specific hydrogen bonds? 1) The concept of base pairing by hydrogen bonding between pyrimidines and purines on the same strand turned out to be a vital clue to the double-stranded structure of the DNA molecule. 2)The concept of base pairing by hydrogen bonding between pyrimidines and pyrimidines on opposite strands turned out to be a vital clue to the double-stranded structure of the DNA molecule. 3) The concept of base pairing by hydrogen bonding between pyrimidines and purines on opposite strands turned out to be a vital clue to the double-stranded structure of the DNA molecule. 4) The concept of base pairing by hydrogen bonding between purines and purines on opposite strands turned out to be a vital clue to the double-stranded structure of the DNA molecule.

3) The concept of base pairing by hydrogen bonding between pyrimidines and purines on opposite strands turned out to be a vital clue to the double-stranded structure of the DNA molecule.

The largest particles that can enter the nucleus without an NLS attached are 9 nm in diameter, whereas particles as large as 26 nm in diameter can enter the nucleus if they are attached to an NLS. What is the best interpretation of this experiment? 1) The concentration of large particles in the nucleus disfavors diffusion into the nucleus. 2) Large (26-nm) particles cannot diffuse through two membranes. 3) The importin-NLS system is capable of carrying 26-nm particles into the nucleus.

3) The importin-NLS system is capable of carrying 26-nm particles into the nucleus.

Many of the proteins of the nuclear envelope appear from electrophoretic analysis to be the same as those found in the endoplasmic reticulum. 1) The proteins in the nuclear envelope that are probably caught in transit are the same as those found in the endoplasmic reticulum.. 2) The nuclear membranes are changed during electrophoretic analysis so that they become similar to those of the endoplasmic reticulum. 3) The nuclear membranes and the endoplasmic reticulum are likely to have a common origin.

3) The nuclear membranes and the endoplasmic reticulum are likely to have a common origin.

What are the properties of DNA polymerase I? 1) It has 5' > 3' exonuclease activity 2) It removes the RNA primer 3) It can polymerize new DNA that has been damaged and removed. 4) It has proofreading ability 5) All of the above 6) 1 and 2 only

5) All of the above

You are using genetic engineering to design a protein that needs to be synthesized in the cytoplasm and then localized in the nucleus of the cell. To accomplish this, you could add 1) a nucleotide or few nucleotides to the DNA sequence for the protein. 2) inverted repeats to the DNA sequence for the protein. a series of specific polysaccharides to the carboxyterminal end of the protein. 3) a DNA sequence for a nuclear localization signal into the DNA that will be present in the mature protein. 4) the protein during mitosis, at a time when the nuclear membrane is dispersed.

3) a DNA sequence for a nuclear localization signal into the DNA that will be present in the mature protein.

What would the predicted result be if Griffith injected mice with a mixture of heat-killed R bacteria and living S bacteria? 1) All mice would die, but only if DNAse was added to the mixture prior to injection. 2) All mice would live, but only if DNAse was added to the mixture prior to injection. 3) All mice would die. 4) All mice would live.

3) all mice would die.

A 40-year-old patient has been diagnosed with cancer. Sequencing of cancer cell genomes reveals a high frequency of G/C to A/T base pairs conversion. The DNA repair system that is most likely deficient in this patient is the 1) nonhomologous end-joining pathway. 2) synthesis-dependent strand annealing pathway. 3) base excision repair pathway. 4) nucleotide excision repair pathway.

3) base excision repair pathway.

If a mutant cell line lacks snRNPs, what would be different from the nonmutant cell line from which the mutant was derived? 1) More total RNA would be present. 2) mRNA lifetimes would be longer. 3) mRNA lengths would be different. 4) tRNA would replace mRNA.

3) mRNA lengths would be different

The situation in which an active regulatory protein "turns off" gene expression is an example of 1) unique regulation. 2) positive control. 3) negative control. 4) constitutive gene elements. 5) a mutation.

3) negative control.

DNA replication 1) is conservative. 2) is partially regulated by promoter/terminator sites. 3) requires a type of RNA polymerase. 4) proceeds by making two continuous strands. 5) is not edited once polymerization has occurred.

3) requires a type of RNA polymerase.

Which of the following is the best definition for consensus sequence, for example, in a bacterial promoter 1) sequence of DNA found in all bacterial promoters 2) sequence of DNA similar to that found in all bacterial promoters 3) sequence of DNA representing the most frequent nucleotide found at every position in all bacterial promoters 4) the best possible DNA sequence to make a bacterial promoter

3) sequence of DNA representing the most frequent nucleotide found at every position in all bacterial promoters

One mechanism that may lead to novel disease treatment involves ________, which hinders the translation of specific mRNAs. 1) rRNA 2) P bodies 3) siRNA 4) macro-RNAs 5) tRNA

3) siRNA

Which of the following accurately identifies the chemical basis of Chargaff's rule? 1) the ionic interactions of the negatively charged phosphates with positively charged histone proteins 2) the presence of deoxyribose instead of ribose 3) the hydrogen bonding properties of the DNA bases 4) the covalent bonding of the sugar-phosphate backbone

3) the hydrogen bonding properties of the DNA bases

If you found an old sample in a lab freezer and it contained a lot of histone protein, from what kind of study could the sample have come? 1) study on nucleosomes 2) study of condensed chromosomes 3) study of the double helical structure of DNA 4) 1 and 2 5) 2 and 3

4) 1 and 2

One strand of a region of DNA has the sequence 5'-ATTCCG-3'. The complementary strand for this one is __________. 1) 5'-ATTCCG-3' 2) 5'-ACCTTA-3' 3) 5'-TAAGGC-3' 4) 5'-CGGAAT-3'

4) 5'-CGGAAT-3'

Which of these statements is NOT true of the nucleolus? 1) It contains a nucleolus organizer region. 2) It contains fibrils of rDNA. 3) It synthesizes rRNA. 4) It is connected to the nucleus via nuclear pores.

4) It is connected to the nucleus via nuclear pores.

For a double-stranded DNA molecule in which 40% of the bases are either G or T, what can you conclude about its content of the base A? 1) 20% of the bases must be A. 2) 30% of the bases must be A. 3) 40% of the bases must be A. 4) 60% of the bases must be A. 5) It is impossible to determine.

5) It is impossible to determine.

Of what significance to Hershey and Chase was the following suggestion (made in 1951 by R. M. Herriott)? "A virus may act like a little hypodermic needle full of transforming principles; the virus as such never enters the cell; only the tail contacts the host and perhaps enzymatically cuts a small hole through the outer membrane and then the nucleic acid of the virus head flows into the cell." 1) This was the very hypothesis that their experiment was designed to test; all that was left to do was determine how to get the entire virus into the target cells. 2) It allowed them to use radioactive labeling, because they could label virus tails and this label would identify whether the nucleic acid can get through the outer membrane. 3) This was the very hypothesis that their experiment was designed to test; all that was left to do was determine how to protect the cell from viral infection. 4) This was the very hypothesis their experiment was designed to test; all that was left to do was to devise a means of identifying the nucleic acid if it did indeed "flow into the cell."

4) This was the very hypothesis their experiment was designed to test; all that was left to do was to devise a means of identifying the nucleic acid if it did indeed "flow into the cell."

If you were to try and pair a thymine with a cytosine (a non Watson-Crick base pairing), then would you expect to see any stability with respect to the hydrogen bonding (assuming the geometrical configurations of both bases were favorable to each other)? If yes, then how many hydrogen bonds could form between these two bases? 1) No, hydrogen bonds cannot form between thymine and cytosine. 2) Yes, one hydrogen bond could form between thymine and cytosine. 3) Yes, three hydrogen bonds could form between thymine and cytosine. 4) Yes, two hydrogen bonds could form between thymine and cytosine

4) Yes, two hydrogen bonds could form between thymine and cytosine.

Which of the following processes is/are associated with the modification of histone proteins in vivo? 1) acetylation 2) transhydroxylation 3) alkylation 4) acetylation and methylation 5) methylation

4) acetylation and methylation

A lac I - mutant would 1) not induce lacZYA in the presence of lactose. 2) not metabolize lactose. 3) not transport lactose into the cell effectively. 4) express lacZYA constitutively. 5) not have β-galactosidase activity.

4) express lacZYA constitutively.

DNA repair in eukaryotes and prokaryotes 1) relies on DNA polymerases to correct all mutations. 2) is very ineffective. 3) relies on completely different mechanisms. 4) is accomplished by multiple specialized pathways. 5) can only repair abnormal nucleotides such as pyridine dimers and depurinated bases.

4) is accomplished by multiple specialized pathways.

Which of the following events signals the end of the initiation phase of bacterial transcription? 1) formation of the first phosphodiester bond between the 2) first two nucleotides of the nascent mRNA 3) binding of RNA polymerase to the promoter 4) loss of the sigma factor from the RNA polymerase 5) unwinding of the DNA

4) loss of the sigma factor from the RNA polymerase

Ultraviolet (UV) light-treated bacteria would have increased DNA damage in the form of 1) analog incorporation. 2) direct transition of the bases. 3) intercalation of the bases. 4) pyrimidine dimer formation. 5) deamination.

4) pyrimidine dimer formation.

Cells that are very sensitive to UV radiation most likely have a defect in the 1) nonhomologous end-joining pathway. 2) synthesis-dependent strand annealing pathway. 3) base excision repair pathway. 4) SOS repair pathway. 5) nucleotide excision repair pathway.

5) nucleotide excision repair pathway.

The nuclear envelope functions as a 1) means of sequestering many of the mRNA processing activities from the cytosol. 2) selective barrier, allowing certain substances in or out. 3) means of separating nuclear and cytoplasmic constituents. 4) means of localization of the chromosomes within the cell. 5) selective barrier that separates nuclear and cytoplasmic constituents, localizes chromosomes within the cell, and sequesters many of the mRNA processing activities from the cytosol.

5) selective barrier that separates nuclear and cytoplasmic constituents, localizes chromosomes within the cell, and sequesters many of the mRNA processing activities from the cytosol.

Numerous Xenopus cells were exposed to varying amounts of ultraviolet light. Some of the resulting cells were observed to lack nucleoli. As a result, one would expect that the cell could not 1) perform cellular respiration. 2) perform photosynthesis. 3) perform cellular respiration or replicate its DNA. 4) replicate its DNA. 5) synthesize ribosomal RNA.

5) synthesize ribosomal RNA.

Which if the following normally functions to lower the pH of the cytosol?

A Na+ -Independent CI^-, HCO3^- exchanger in the plasma membrane

A strain of mutant bacteria has been isolated. You isolate the mRNA to only this mutated gene in this bacterial strain to use in an in vitro translation system and note that even in vitro it is difficult to use this RNA and obtain protein. A protein is made for a control (wild type) mRNA. Of the following, which is a likely explanation for these results? A) There may be a mutation in the Shine-Dalgarno sequence of the DNA, resulting in mRNA that binds poorly to the ribosome. B) There may be a mutation in the ribosomal rRNA recognizing the Shine-Dalgarno sequence of the message. C) This mutant may have altered tRNA molecules, such that the codon-anticodon interaction during translation is affected. D) This mutant may not manufacture enough translation factors for effective translation. E) In this mutant, the ribosomal subunits may not associate well enough for effective translation.

A) There may be a mutation in the Shine-Dalgarno sequence of the DNA, resulting in mRNA that binds poorly to the ribosome.

Eukaryotic mRNAs A) are translated after they are exported from the nucleus B) are transcribed and translated simultaneously C) must be folded into the correct three-dimensional shape before they can be translated D) are processed in the same way as prokaryotic mRNAs

A) are translated after they are exported from the nucleus

DNA replication A) requires a type of RNA polymerase. B) is partially regulated by promoter/terminator sites. C) proceeds by making two continuous strands at one replication fork. D) is not edited once polymerization has occurred. E) is conservative

A) requires a type of RNA polymerase.

8. Which of the following is correct regarding the composition of various biological membranes? A. Bacterial plasma membranes are often composed of one main type of phospholipid and lack cholesterol. B. Cholesterol in the eukaryotic plasma membrane induces phase transition to the gel state. C. Inositol phospholipids are the most abundant lipids in the endoplasmic reticulum membrane. D. The mitochondrial and bacterial membranes are rich in glycolipids. E. Yeast cells synthesize more fatty acids with cis¬-double bonds when the temperature in the environment rises.

A. Bacterial plasma membranes are often composed of one main type of phospholipid and lack cholesterol.

7. Which of the following changes would you expect to increase the phase transition temperature of a synthetic bilayer composed of phosphatidylserine? A. Incorporation of phospholipids with longer fatty acid chains. B. Introduction of double bonds in the fatty acids. C. Addition of cholesterol. D. Removal of serine from the head group. E. None of the above.

A. Incorporation of phospholipids with longer fatty acid chains.

Sanshool is a natural compound found in Sichuan pepper, which is commonly used in making spicy Asian food, and creates a numbing sensation in the mouth. It is known to inhibit a subset of potassium leak channels involved in maintaining the resting membrane potential in sensory neurons. How do you think sanshool affects these sensory neurons? A. It elevates the resting potential (to less negative values) and makes it easier to excite the neuron. B. It elevates the resting potential and makes it harder to excite the neuron. C. It lowers the resting potential and makes it easier to excite the neuron. D. It lowers the resting potential and makes it harder to excite the neuron. E. It causes hyperpolarization and decreases the spontaneous firing of the neuron.

A. It elevates the resting potential (to less negative values) and makes it easier to excite the neuron.

The lactose permease in Escherichia coli is an H+ -lactose symporter that mediates the inward active transport of lactose if this sugar is present in the environment instead of glucose. Which of the following is true about this transporter? A. It has a twofold pseudosymmetrical structure. B. Lactose and H+ bind to two different conformations of the transporter. C. The transporter goes through an intermediate state in which the bound lactose is open to both sides of the membrane. D. If lactose and H+ concentrations are changed sufficiently, the transporter can act as an H+-lactose antiporter. E. All of the above.

A. It has a twofold pseudosymmetrical structure.

10. Many cells store lipids in droplets of varying sizes. These droplets ... A. are enclosed by a phospholipid monolayer (instead of a bilayer). B. mostly store cholesterol and phospholipids. C. are produced by and released from the Golgi apparatus. D. have mostly protein-free bilayer membranes. E. are composed primarily of charged amphiphilic lipids.

A. are enclosed by a phospholipid monolayer (instead of a bilayer).

9. The two monolayers of the plasma membrane in a human red blood cell ... A. have different overall electrical charges, with negatively charged phospholipids (e.g. phosphatidylserine) normally enriched in the inner monolayer. B. have the same abundance of phosphatidylinositol. C. exchange phospholipids only through spontaneous flip-flops. D. both contain glycolipids. E. both contain gangliosides.

A. have different overall electrical charges, with negatively charged phospholipids (e.g. phosphatidylserine) normally enriched in the inner monolayer.

The membrane potential in a particular hyper polarized cell is measured to be -70 mV. For each of the following channels in this cell, the calculated Nernst equilibrium potential for the corresponding ion is passed. Indicate whether each channel is driven to pass the ion into (I) or out (O) of the cell. Your answer would be a four-letter string composed of letter I and O only

All I

Myelination of axons in the peripheral nervous system...

All of the above

An ion channel...

All the above 1. Always mediates passive transport 2. Is ion-selective 3. Is typically several orders of magnitude faster than a transporter 4. Is usually gated

Which of the following graphs better represents the change in the relative conductance of Na+ and K+ channels during an action of potential in a neuronal membrane?

B - K+ is before Na+

When examining a five-carbon sugar to determine if it is ribose or deoxyribose, one looks to see if there are two H's on the ________ carbon in the structure. A) 1' B) 2' C) 3' D) 4' E) 5'

B) 2'

During DNA replication, DNA polymerase intiiates a completely new DNA strand from scratch. A) True B) False

B) False

Primase requires a proofreading function that ensures there are no errors in the RNA primers used for DNA replication. A) True B) False

B) False

The formation of heterochromatin maintains the other genes in a transcriptionally silent (unexpressed) state. Which histone modification directs the formation of the most common type of heterochromatin? A) H3Lys4 met B) H3Lys9 met C) H3Lys14 met D) H3Lys27 met

B) H3Lys9 met

What type of enzyme removes damaged DNA from the rest of the DNA molecule? A) Polymerase B) Nuclease C) Primase D) Ligase E) Helicase

B) Nuclease

Single nucleotide changes have deleterious effects on the proteins they encode. Explain your answer. A) Always B) Sometimes C) Never

B) Sometimes

Which part of a protein is synthesized by a ribosome first? A) The C-terminus B) The N-terminus C) RNA binding domain D) 5' methyl guanosine cap

B) The N-terminus

Enzymes that add ubiquitin to proteins have been found in the nucleus of eukaryotic cells. These enzymes would be most likely to regulate gene expression by __________. A) causing a change in which introns are removed and changing the mature mRNA B) causing degradation of transcription factors and changing which genes are expressed C) causing degradation of histones and changing chromatin structure D) causing activation of enhancer-binding proteins

B) causing degradation of transcription factors and changing which genes are expressed

The chromosome of a bacterial cell possesses the following genotype with regard to the lac operon: I−P+O+Z+Y−A−. This bacterial cell would A) make β-galactosidase only in the presence of lactose. B) make β-galactosidase independently of lactose. C) make β-galactosidase and galactoside permease in the presence of lactose. D) make transacetylase in the presence of lactose. E) make no lac gene products.

B) make β-galactosidase independently of lactose.

If you were designing a method to specifically inhibit prokaryotic transcription, but not eukaryotic transcription, interfering with which of the following would work best? A) an intercalating agent B) recognition of the prokaryotic promoter by a sigma factor C) DNase activity D) RNA polymerase II activity E) ribosomal binding to mRNA

B) recognition of the prokaryotic promoter by a sigma factor

You are studying a eukaryotic gene whose initial transcript is 1500 nucleotides in length. The mature mRNA derived from the gene is 1200 nucleotides in length. What is the most probable reason for the discrepancy? A) a mutation that results in a shorter product B) removal of introns C) removal of exons D) mRNA breakage E) A mutation that results in a shorter product or mRNA breakage could have occurred.

B) removal of introns

An isolate of a mutant bacterium appears to grow more slowly than the wild-type population from which it was isolated. Further studies showed that the slower growth was due to a markedly reduced DNA polymerase I activity. From this information, one would expect that this organism would also be deficient in the activity of DNA A) translocation into ER B) replication C) transcription. D) translation. E) primers required for DNA replication.

B) replication

Voltage-gated cation channels in the plasma membrane of a neuron open when the membrane potential passes a threshold value that is about 20 mV above the resting potential. This corresponds to a change of about 4 × 106 newtons per coulomb in the magnitude of the electric field across the membrane compared to the resting state. The tetrameric channels have a voltage-sensing helix S4 in each of their four subunits. Most S4 helices contain seven residues with positively charged side chains. The charge carried by each such residue is about 1.6 × 10-19 coulombs. By reaching threshold depolarization, what are the magnitude and the direction of the collective force that the four S4 helices in the channel experience as a result of the change in the electric field? The force that particles of charge q in an electric field E experience is calculated as F = q.E. A. 18 pN, toward the cell interior B. 18 pN, toward the cell exterior C. 90 pN, toward the cell interior D. 90 pN, toward the cell exterior E. 45 pN, toward the cell interior

B. 18 pN, toward the cell exterior

1. What is the typical thickness of a lipid bilayer such as the plasma membrane of our cells? A. 0.5 nm B. 5 nm C. 50 nm D. 100 nm E. 500 nm

B. 5 nm

6. Why do liposomes not fuse with one another spontaneously when suspended in an aqueous environment? A. Because fusion requires a large number of flip-flops, which are very rare. B. Because the hydration shell of the polar head groups of the lipids needs to be removed. C. Because fusion requires micelle formation. D. Because of the rapid lateral diffusion and rotation of the lipid molecules.

B. Because the hydration shell of the polar head groups of the lipids needs to be removed.

In neurons, the synaptotagmin-1 protein is localized to presynaptic axon terminals. When activated, it facilitates the fusion of neurotransmitter-containing synaptic vesicles to the plasma membrane, leading to neurotransmitter release into the synaptic cleft. Which of the following would you expect to directly activate synaptotagmin-1 for this function? A. Binding to Mg2+ B. Binding to Ca2+ C. Binding to phosphatidylcholine D. Binding to K+ E. Binding to the K+ leak channels

B. Binding to Ca2+

MscS and MscL are mechanosensitive channels that ... A. constitute the majority of channel proteins in the plasma membrane of auditory hair cells in the human cochlea. B. open in response to membrane tension. C. open at the same osmotic pressure, but differ in their ion selectivity. D. are highly ion selective. E. All of the above.

B. open in response to membrane tension.

Astrogial cells in the brain can actively import the amino acids glutamate from the synaptic cleft, convert it to the amino acid glutamine, and release the glutamine into the cleft to glutamate Why is this function of glial cells important?

Because glutamate is an excitatory neurotransmitter and should be cleared from the synaptic cleft rapidly after its release

Why do cells not have membrane transport proteins for O2?

Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly without the need for a transporter

In neurons, the synapotagmin-1 protein is localized to presynaptic axon terminal. When activated, t facilitates the fusion of neurotransmitter-containing synaptic vesicles to the plasma membrane, leading to neurotransmitter release into the synaptic cleft. Which of the following would you expect to directly activate synaptotagmin-1 for this function?

Binding to Ca2+

In a voltage-clamp experiment on a squid giant axon, the membrane potential is clamped at +20 mV, as shown below. Within the same time frame, which of the curves A to D better show qualitatively how the total membrane current changes? A positive value of the current represents an outward flow of cations.

C - bigger dotted line

You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 constains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusions? A) single-stranded genomes always have a larger percentage of purines B) using the formula: G - A = C + T C) Double-stranded genomes have equal amounts of A and T D) Single-stranded genomes have a higher rate of mutation

C) Double-stranded genomes have equal amounts of A and T

In eukaryotes, where do transcription regulators bind? A) Upstream from a gene B) Downstream from a gene C) Either upstream or downstream from a gene D) The TATA box

C) Either upstream or downstream from a gene

In eukaryotes, which parts of a gene are transcribed into RNA? A) Introns B) Exons C) Introns and exons

C) Introns and exons

The core histones are small, basic proteins that have a globular domain at the G-terminus and a long extended conformation at the N-terminus. Which of the following is NOT true of the N-terminal "tail" of these histones? A) It is subject to covalent modifications B) It extends out of the nucleosome core C) It binds to DNA in a sequence-specific manner D) It helps DNA pack tightly

C) It binds to DNA in a sequence-specific manner

Which of the following statements is NOT true concerning peptidyl transferase? A) It is a ribozyme having catalytic activity. B) It catalyzes peptide bond formation. C) It moves the ribosome, so translation continues. D) It is associated with the large subunit of ribosomes. E) It requires no outside source of additional energy, such as ATP.

C) It moves the ribosome, so translation continues.

In eukaryotic initiation, one will often see the sequence ACCAUGG as a translational start sequence. This sequence is known as the ________ sequence. A) Okazaki B) ETS (eukaryotic translational start) C) Kozak D) IRES (internal ribosome entry sequence) E) CIBS (complex initiation binding sequence)

C) Kozak

A mutation in the sigma factor of RNA polymerase occurs. What is the level of transcription that would occur compared to normal? A) No change in the level of transcription B) Less transcriptional efficiency than normal C) No transcription will occur

C) No transcription will occur

What statement about nucleosomes is FALSE? A) A nucleosome is a "bead" on a strong of unfolded chromatin B) A nucleosome produces a 3-fold packing ratio of DNA C) Nucleosomes are found only in mitotic chromosomes D) A nucleosome consists of DNA wrapped around 8 histone proteins, plus a short segment of linker DNA

C) Nucleosomes are found only in mitotic chromosomes

Indicate the implications for nuclear structure or function of the following experimental observation. Sucrose crosses the nuclear envelope so rapidly that its rate of movement cannot be accurately measured. A) There is a small concentration difference between two sides of the nuclear envelope that forces sucrose to move very fast. B) Sucrose can dissolve the nuclear envelope because of its polarity. After sucrose molecules have passed, nuclear envelope goes back to its initial state. C) Unlike most membranes, the nuclear envelope appears to be freely permeable to a polar organic molecule. D) The nuclear envelope has pores that are designed to transport sucrose molecules so that they can cross it without any resistance.

C) Unlike most membranes, the nuclear envelope appears to be freely permeable to a polar organic molecule.

Within the ribosome, the formation of peptide bonds is catalyzed by: A) aminoacyl-tRNA synthetase B) the tRNA itself C) an RNA molecule in the large ribosomal subunit D) a peptidase in the small ribosomal subunit E) the release factor

C) an RNA molecule in the large ribosomal subunit

The transfer of polypeptides into the ER is called A) transit sequence import. B) post-translational import. C) cotranslational import. D) endoplasmic import. E) ribosomal import.

C) cotranslational import.

The energy needed to polymerize DNA is supplied by A) the hydrolysis of the phosphate bonds of ATP by an accessory protein that is part of the DNA polymerase holoenzyme. B) the hydrolysis of the phosphate bonds of ATP or GTP, depending on the form of DNA polymerase. C) the hydrolysis of the phosphate bonds of the deoxynucleoside triphosphates that are being added to the new DNA chain. D) the formation of the covalent bond between the phosphate of the nucleoside and the hydroxyl group. E) the hydrolysis of the RNA primers used in DNA replication.

C) the hydrolysis of the phosphate bonds of the deoxynucleoside triphosphates that are being added to the new DNA chain.

Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by ______. A) recruiting other enzymes B) modifying the C-terminal tails of core histones C) using the energy of ATP hydrolysis to move nucleosomes D) denaturing DNA by interfering with hydrogen-bonding between base pairs

C) using the energy of ATP hydrolysis to move nucleosomes

Which of the following normally functions to lower the pH of the cytosol? A. A Na+-H+ exchanger in the plasma membrane. B. A Na+-driven Cl--HCO3- exchanger in the plasma membrane. C. A Na+-independent Cl--HCO3-exchanger in the plasma membrane. D. A V-type ATPase in the lysosomal membrane. E. Both answers A and B above.

C. A Na+-independent Cl--HCO3-exchanger in the plasma membrane.

Why do cells not have membrane transport proteins for O2? A. Because they need to keep the oxygen concentration low inside the reducing environment of the cell. B. Because oxygen can dissolve in water and leak in via water channels. C. Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly without the need for a transporter. D. Because oxygen is transported in and out of the cell in special oxygen-carrying proteins such as hemoglobin. E. Because oxygen transport across a membrane is energetically unfavorable.

C. Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly without the need for a transporter.

Which of the following situations in a neuron results in action potentials that have extended depolarization phases? A. Inhibiting the voltage-gated Na+ channels. B. Stimulating the voltage-gated K+ channels. C. Compromising the inactivation mechanism in voltage-gated Na+ channels. D. Compromising the inactivation mechanism in voltage-gated K+ channels. E. None of the above.

C. Compromising the inactivation mechanism in voltage-gated Na+ channels.

Imagine a small synthetic vesicle made from pure phospholipids enclosing an interior lumen containing 1 mM glucose and 1 mM sodium chloride. If the vesicle is placed in pure water, which of the following happens faster? A. Na+ diffuses out. B. Cl- diffuses out. C. H2O diffuses in. D. Glucose diffuses out. E. Sodium chloride diffuses out.

C. H2O diffuses in.

Once expressed in a neuron in the mouse brain and subjected to a flash of light, how does channelrhodopsin affect the membrane potential? A. It causes neurotransmitter release, leading to an action potential in the postsynaptic neuron. B. It increases the membrane permeability to cations and makes the membrane potential more negative. C. It depolarizes the membrane, leading to the opening of voltage-gated Na+ channels. D. It hyperpolarizes the membrane, leading to the inactivation of voltage-gated K+ channels. E. It changes the membrane potential such that voltage-gated K+ channels but not voltage-gated Na+ channels are activated.

C. It depolarizes the membrane, leading to the opening of voltage-gated Na+ channels.

Which of the following is the reason why an aquaporin does not pass ions (such as Na+) through? A. The Na+ ions are too small to pass through the pore rapidly enough. B. The Na+ ions are too large to pass through the narrow pore. C. The Na+ ions do not favorably interact with the wall of the pore and therefore cannot be dehydrated. D. Two Asn residues in the channel prevent the passage of Na+ ions. E. A Na+ ion must become fully hydrated to pass through.

C. The Na+ ions do not favorably interact with the wall of the pore and therefore cannot be dehydrated.

5. The motion of lipid molecules in a synthetic bilayer can be studied by various techniques. Which of the following has been observed in these systems? A. Phospholipids diffuse rapidly within and between the two leaflets of a bilayer. B. An average lipid molecule can diffuse the length of about 2 micrometers in a fraction of a millisecond. C. The flip-flops are very rare for phospholipids but cholesterol molecules flip-flop more often. D. Within a bilayer, lipid molecules rarely rotate about their long axis, but diffuse laterally at very high rates. E. All of the above.

C. The flip-flops are very rare for phospholipids but cholesterol molecules flip-flop more often.

In contrast to transporters, the channel proteins in cellular membranes ... A. interact strongly with the solute(s) that they transport. B. undergo a conformational change every time they transport a solute. C. can only mediate passive transport. D. form pores that are always open.

C. can only mediate passive transport.

A potassium channel conducts K+ ions several orders of magnitude better than Na+ ions, because ... A. the Na+ ion is too large to pass through the channel pore. B. the hydrated Na+ ion occupies a larger volume compared to the hydrated K+ ion, and is too large to pass through the channel pore. C. the Na+ ion is too small to interact with the channel in a way that facilitates the loss of water from the ion. D. the Na+ ion cannot bind to the high-affinity K+-binding sites in the channel pore.

C. the Na+ ion is too small to interact with the channel in a way that facilitates the loss of water from the ion.

Many amino acids in our diet are absorbed via the transcellular transport pathway by the intestinal epithelial cells. This process requires ATP hydrolysis by ... A. the Na+-amino acid symporters in the apical domain of the plasma membrane. B. the Na+-amino acid antiporters in the apical domain of the plasma membrane. C. the Na+-K+ pumps in the basal and lateral domains of the plasma membrane. D. the amino acid carriers in the basal domain of the plasma membrane. E. F-type ATPases in the apical domain of the plasma membrane.

C. the Na+-K+ pumps in the basal and lateral domains of the plasma membrane.

The permeability of a protein-free lipid bilayer to various molecules depends on their properties. Sort the following in order of low to high permeability from left to right. Your answer would be a six-digit number composed of digits 1 to 6, e.g. 123456. (A)O2 (B) ATP (C) RNA oligonucleotide (D)Na+ (E) Glucose (F) Urea

CBDEFA

the activator for the lac operon is

CRP

In contrast to transporters, the channel proteins in cellular membranes...

Can only mediate passive transport

A membrane potenial is plotted over time in the following graph. The Nernst equilibrium potentials for four ions (A to D) that affect the membrane potential in this system are indicated in the graph. What happened in the time period indicated by a question mark?

Channels conducting ion D opened

Which of the following situations in a neuron results in action potentials that have extended depolarization phases?

Compromising the inactivation mechanism in voltage-gated Na+ channels

Heterochromatin is highly ________, thus constitutive heterochromatin plays a(n) ________ role and facultative heterochromatin functions in ________. A) denatured; structural; regulation of gene expression B) compacted; regulatory; structure C) denatured; regulatory; structure D) compacted; structural; regulation of gene expression E) modified; evolutionary; structure

D) compacted; structural; regulation of gene expression

The accompanying graph shows a growth curve of E. coli growing in a defined medium containing equal molar amounts of glucose and lactose. Based on your knowledge of the regulation of the lac operon, the best explanation of these results is that A) early on, due to the presence of lactose, the bacteria use the lac operon. Glucose is used later. B) the bacteria use both sugars simultaneously. C) the presence of glucose causes the formation of cAMP catabolic repressor protein (CRP) complexes, which shut down the lac operon until the glucose is used up. D) glucose is used first. Once glucose becomes limiting, intracellular cAMP increases, forming cAMP-CRP complexes that activate the lac operon to use lactose. E) early on the glucose binds to the repressor protein lacI and shuts down the lac operon.

D) glucose is used first. Once glucose becomes limiting, intracellular cAMP increases, forming cAMP-CRP complexes that activate the lac operon to use lactose.

A NASA probe returned samples of rocks from the surface of Mars. From these rocks, a prokaryotic organism was isolated and remained viable under conditions similar to those of Mars. The organisms are capable of dividing to replicate themselves. In order to determine whether the DNA replication of these organisms was semiconservative, an experiment using N15/N14 (similar to that of Meselson and Stahl) was performed. If the method of DNA replication were conservative, after one generation one would expect to see A) all of the DNA in the heavy (N15) band. B) all of the DNA in the light (N14) band. C) all of the DNA at a point midway between the heavy and light bands. D) half of the DNA in the light band, the other half in the heavy band. E) None of these are correct.

D) half of the DNA in the light band, the other half in the heavy band.

Which of the following is an example of translational regulation? A) protein degradation B) DNA splicing C) protein folding D) mRNA degradation E) DNA methylation

D) mRNA degradation

Which of the following is the correct order of the levels of DNA packaging in eukaryotic chromosomes? A) chromatin fiber → heterochromatin → nucleosome → looped domains B) nucleosome → looped domains → chromatin fiber → heterochromatin C) heterochromatin → nucleosome → chromatin fiber → looped domains D) nucleosome → chromatin fiber → looped domains → heterochromatin E) chromatin fiber → nucleosome → looped domains → heterochromatin

D) nucleosome → chromatin fiber → looped domains → heterochromatin

You have isolated a piece of DNA that you believe contains an interesting gene. Using a mix of RNA polymerase and ribonucleotides, you perform in vitro transcription. However, even though all of your controls work, no mRNA is created from your DNA fragment. Working backward, you note that your DNA preparation removed approximately 250 base pairs from the 5' end of the gene. The most likely explanation to explain the lack of transcription is A) the termination signal was removed. B) the RNA polymerase became inactivated. C) the 5' methyl guanosine cap was removed. D) the promoter was removed. E) None of these explains the negative results.

D) the promoter was removed.

20. Which of the following proteins is NOT in the same superfamily as the other four? The other four share an overall architecture composed of seven closely-packed transmembrane helices. A. Bacteriorhodopsin B. Channelrhodopsin C. G-protein-coupled receptor D. Aquaporin E. Rhodopsin

D. Aquaporin

Astroglial cells in the brain can actively import the amino acid glutamate from the synaptic cleft, convert it to the amino acid glutamine, and release the glutamine into the cleft to be subsequently taken up by the presynaptic neurons. The neurons then convert it back to glutamate. Why is this function of glial cells important? A. Because it competes with and replaces the direct uptake of glutamate by the neurons and thus regulates neuronal function. B. Because neurons cannot produce the amino acids glutamine and glutamate and rely on the glial cells for their supply. C. Because glutamate cannot be taken up directly by the neurons. D. Because glutamate is an excitatory neurotransmitter and should be cleared from the synaptic cleft rapidly after its release. E. Because glutamate import through glutamate-Na+ symporters in the glial cells is required for the maintenance of Na+ concentration in the synaptic cleft

D. Because glutamate is an excitatory neurotransmitter and should be cleared from the synaptic cleft rapidly after its release.

This family of ATPases is structurally related to the turbine-like pumps that acidify lysosomes and vesicles; however, they usually function in reverse, generating ATP from ADP and Pi using proton gradients across membranes. What are they called? A. P-type pumps B. ABC transporters C. V-type pumps D. F-type pumps E. Permeases

D. F-type pumps

14. Integrins are single-pass integral membrane proteins in the plasma membrane of animal cells and are involved in the interaction of the cell with the surrounding extracellular matrix. Which of the following descriptions do you think matches the transmembrane part of an integrin molecule? A. It forms a β barrel. B. It is an α helix that is bent in the middle. C. It is about 10 amino acids long, with every other amino acid side chain being hydrophobic. D. It folds in a conformation with maximal intrachain hydrogen-bonding. E. It is about 100 amino acids long.

D. It folds in a conformation with maximal intrachain hydrogen-bonding.

Which of the following transporters is NOT electrogenic? A. Na+-glucose symporter B. Ca2+-pump C. Na+-K+ pump D. Na+-independent Cl--HCO3- exchanger E. Bacteriorhodopsin

D. Na+-independent Cl--HCO3- exchanger

13. Transmembrane proteins ... A. are typically exposed only to one side of the membrane. B. can be released from the membrane by a gentle extraction procedure such as salt treatment. C. are often further attached to the membrane via a GPI anchor. D. are sometimes covalently attached to a fatty acid chain that inserts into the membrane. E. cannot contain β sheets in the part of their structure that interacts with the membrane interior.

D. are sometimes covalently attached to a fatty acid chain that inserts into the membrane.

19. On the plasma membrane of the archaeon Halobacterium salinarum, bacteriorhodopsin is found in high density in patches of purple membrane. This protein ... A. is a light-gated anion channel. B. is a single-pass transmembrane protein. C. uses the energy stored in the proton gradient to transport small molecules. D. changes conformation in response to light. E. All of the above.

D. changes conformation in response to light.

Aquaporin has a pair of key asparagine residues located on the wall almost halfway through its pore. These residues simultaneously bind to the oxygen atom of a passing water molecule, rendering it unavailable for hydrogen-bonding. As a result, ... A. the channel can conduct negatively charged (but not positively charged) ions. B. the channel can conduct glycerol as well as water. C. the channel cannot conduct glycerol. D. the channel cannot conduct protons. E. the channel cannot conduct chloride ions.

D. the channel cannot conduct protons.

Which of the following are components of Chargaff's rules of bases? A) % purines = % pyrimidines B) %C + %T = %A + %G C) %A = %T D) %G = %C E) All of these are true.

E) All of these are true.

Which of the following is not a true statement regarding the genetic code? A) The genetic code is degenerate. B) The genetic code is nearly universal, with only a few minor exceptions. C) The genetic code is nonoverlapping. D) The genetic code is triplet-based. E) Each codon represents a different amino acid.

E) Each codon represents a different amino acid.

In eukaryotes, post-transcriptional control of gene regulation may involve (choose the best answer) A) alternative mRNA splicing. B) control of nuclear export of mRNAs to the cytoplasm. C) differential mRNA degradation. D) gene amplification and methylation. E) alternative mRNA splicing, control of nuclear export of mRNAs to the cytoplasm, and differential mRNA degradation.

E) alternative mRNA splicing, control of nuclear export of mRNAs to the cytoplasm, and differential mRNA degradation.

DNA damage can occur (choose the best answer) A) due to exposure to certain chemicals or radiation. B) spontaneously. C) during DNA replication. D) during transcription. E) during DNA replication, spontaneously, or due to exposure to certain chemicals or radiation

E) during DNA replication, spontaneously, or due to exposure to certain chemicals or radiation

The action of a new drug is unknown, so you test various aspects of eukaryotic cell processes looking for an effect. You notice that the survival of cells exposed to this drug is very low. Further analysis shows that some proteins and mRNAs are much longer than they should be. One hypothesis is that the drug interferes with A) transcription termination signals. B) spliceosome activity. C) ribosomes. D) nucleoli. E) either transcription termination signals or spliceosome activity

E) either transcription termination signals or spliceosome activity

In DNA replication, the leading strand of DNA ________, while the other newly forming strand, called the lagging strand, ________. A) is synthesized in the 5' → 3' direction; the new DNA is synthesized in the 3' → 5' direction B) is synthesized in the 3' → 5' direction; the new DNA is synthesized in the 5' → 3' direction C) does not require an RNA primer; an RNA primer is required D) is synthesized in a series of short, discontinuous fragments; the new DNA is synthesized as a continuous chain E) is synthesized as a continuous chain; the new DNA is formed in a series of short, discontinuous fragments

E) is synthesized as a continuous chain; the new DNA is formed in a series of short, discontinuous fragments

Which of the following activities is NOT associated with post-translational processing? A) glycosylation B) specific cleavage of polypeptides C) chaperonin activity D) addition of lipid groups E) polyadenylation

E) polyadenylation

Protein phosphorylation, protein folding, and proteolytic cleavage are all examples of A) post-transcriptional control of gene expression and activity. B) epigenetic control of inheritance. C) repression of gene expression. D) induction of gene expression. E) post-translational control of gene expression and activity.

E) post-translational control of gene expression and activity.

. Thymine is used in DNA despite the fact that it is energetically more expensive to synthesize than uracil because A) spontaneous deamination reactions convert cytosine to uracil at a fairly high rate. B) uracil is more sensitive to ultraviolet (UV) damage. C) uracil is more susceptible to depurination. D) uracil can only bind with ribose, not deoxyribose. E) thymine is less likely to undergo spontaneous deamination than uracil

E) thymine is less likely to undergo spontaneous deamination than uracil

The Nernst equilibrium potential for an ion that is 10 times more concentrated in the cytosol compared to the extracellular fluid is about -60 mV. How much would the potential be if the extracellular concentration decreases 100-fold with no change in the intracellular concentration? A. -6000 mV B. -6 mV C. -600 mV D. -20 mV E. -180 mV

E. -180 mV

18. Under certain conditions, about 20 molecules, on average, are predicted to exist in each β-octylglucoside detergent micelle. If the critical micelle concentration for this detergent is about 20 mM under these conditions, at what total β-octylglucoside concentration are about half of the detergent molecules found in micelles? A. 1 mM B. 10 mM C. 20 mM D. 21 mM E. 40 mM

E. 40 mM

12. Glycolipids such as gangliosides ... A. may contain oligosaccharide chains with negatively charged residues. B. are found to constitute about 10% of the total lipid mass in the plasma membrane of neurons. C. are found in the extracellular leaflet (facing away from the cytosol) in the cellular membranes. D. affect the electrical environment of the membrane. E. All of the above

E. All of the above

21. While examining the crystal structure of a membrane protein, you find several phospholipid molecules bound to the protein. You know that these lipids ... A. are thought to help stabilize many membrane proteins. B. may enhance the crystallization of the bound membrane proteins. C. interact specifically with the protein. D. can have head groups of various sizes and charges depending on the protein. E. All of the above.

E. All of the above.

An ion channel ... A. always mediates passive transport. B. is ion-selective. C. is typically several orders of magnitude faster than a transporter. D. is usually gated. E. All of the above.

E. All of the above.

Once expressed in a neuron in the mouse brain and subjected to a flash of light, how does channel rhodopsin affect the membrane potential?

It depolarizes the membrane, leading to the opening of voltage-gate Na+ channels

Myelination of axons in the peripheral nervous system ... A. is carried out by Schwann cells. B. insulates the axons to reduce current leakage. C. increases the speed of action potential propagation through saltatory conduction. D. conserves energy because the active excitations are restricted to the nodes of Ranvier. E. All of the above.

E. All of the above.

24. Which of the following changes is more likely to further confine a membrane protein within a corral established by the cortical cytoskeletal network? A. Increased temperature B. Protease cleavage of the extracellular domain of the protein C. Binding to an extracellular ligand D. Protease cleavage of the cytosolic domain of the protein E. Binding of the protein to other transmembrane proteins

E. Binding of the protein to other transmembrane proteins

Dopamine is a neurotransmitter involved in the reward pathways in the brain, and its decreased activity has been associated with diseases such as Parkinson's disease and attention-deficit/hyperactivity disorder (ADHD). Which of the following drugs is NOT a likely candidate to treat these diseases? A. Methylphenidate, a dopamine reuptake inhibitor B. Amphetamine, a dopamine-releasing agent that triggers the release of dopamine into the synaptic cleft C. Carbidopa, which enhances the availability of the dopamine synthesis precursors in the brain D. Forskolin, a sensitizer of dopamine receptors E. Chlorpromazine, a dopamine antagonist that binds to and inhibits dopamine receptors

E. Chlorpromazine, a dopamine antagonist that binds to and inhibits dopamine receptors

A neuron's repetitive firing rate is limited by an absolute refractory period, during which a new action potential cannot be generated. Which event is chiefly responsible for this limit? A. Opening of K+ leak channels. B. Opening of voltage-gated Na+ channels. C. Opening of transmitter-gated cation channels. D. Inactivation of voltage-gated K+ channels. E. Inactivation of voltage-gated Na+ channels

E. Inactivation of voltage-gated Na+ channels

Which of the following is correct regarding the electrical properties of cellular membranes? A. Setting up (or changing) the membrane potential requires changing the bulk concentrations of the ions on the two sides of the membrane. B. The resting potential in most animal cells is between 20 mV and 120 mV (positive inside). C. If the membrane is impermeable to an ion, the membrane potential approaches the equilibrium potential for that ion. D. The resting potential decays immediately following the inhibition of the Na+-K+ pump by a drug. E. None of the above.

E. None of the above.

4. Which of the following is normally NOT found in a eukaryotic membrane? A. Cholesterol B. Phosphatidylinositol C. Sphingomyelin D. Ganglioside GM1 E. Octylglucoside

E. Octylglucoside

16. What do all β-barrel transmembrane proteins have in common? A. The number of β strands. B. The diameter of the barrel. C. The number of negative peaks in their hydropathy plots. D. The general function, i.e. membrane transport. E. The structural rigidity compared to α-helical transmembrane proteins.

E. The structural rigidity compared to α-helical transmembrane proteins.

A certain neuron in a mouse brain is firing about 300 times per second, whereas almost all of its neighboring neurons are firing at much lower rates of only a few times per second. This implies that ... A. this neuron expresses more depolarizing (Na+ and Ca2+) than hyperpolarizing (K+) channels compared to most of its neighbors. B. the mouse is experiencing an epileptic seizure. C. the refractory period of its voltage-gated Na+ channels is at least 300 ms. D. it releases excitatory neurotransmitters at its axon terminals. E. it is probably of a different type compared to most of its neighbors.

E. it is probably of a different type compared to most of its neighbors.

If the extracellular concentration of sodium ions is artificially decreased for a neuron, ... A. both the resting potential and the peak of the action potential rise significantly. B. the resting potential increases but the action potential peak does not. C. the resting potential hardly changes but the action potential peak is raised. D. the resting potential decreases but the action potential peak is raised. E. the resting potential hardly changes but the action potential peak is lowered.

E. the resting potential hardly changes but the action potential peak is lowered.

Neuromuscular transmission involves the sequential activation of several ion channels. Sort the following events to reflect the sequence leading to muscle contraction. Your answer would be a five-digit number composed of numbers 1 to 5 only, e.g. 12543. (A)Opening of voltage-gated Na+ channels in the muscle cell plasma membrane. (B) Opening of Ca2+ release channels in the sarcoplasmic reticulum membrane. (C) Opening of ionotropic acetylcholine receptors on the muscle cell plasma membrane. (D)Opening of voltage-gated Ca2+ channels in the T tubules. (E) Opening of voltage-gated Ca2+ channels in the motor neuron.

ECADB

The nicotinic acetylcholine receptor is an ionotropic receptor that can be activated by nicotine, a stimulant drug found in cigarettes. Additionally, α-bungarotoxin, a neurotoxin found in the venom of some snakes, binds preferentially and tightly to the closed conformation of the receptors. Another drug, donepezil, is a potent acetylcholinesterase inhibitor used to treat patients with Alzheimer's disease. If applied at a neuromuscular junction, indicate whether each of the compounds (1) acetylcholine, (2) nicotine, (3) α-bungarotoxin, and (4) donepezil would enhance (E) or suppress (S) the Ca2+ influx in the muscle cells. Your answer would be a fourletter string composed of letters E and S only, e.g. EESS

EESE

The nicotinic acetylcholrine receptor is an ionotropic receptor that an be activated by nicotine,

EESE

From left to right, indicate whether the transmitter-gated channels for (1) calcium, (2) chloride, (3) potassium, and (4) sodium at a chemical synapse usually open in response to excitatory (E) or inhibitory (I) neurotransmitter. Your answer would be a four-letter

EIIE

From left to right, indicate whether the transmitter-gated channels for (1) calcium, (2) chloride, (3) potassium, and (4) sodium at a chemical synapse usually open in response to excitatory (E) or inhibitory (I) neurotransmitters. Your answer would be a four-letter string composed of letters E and I only, e.g. EEIE.

EIIE

Most eukaryotic ABC transporters are involved in exporting small molecules from the cytosol. In this subset of the ABC transporters, does the small molecule bind better to the ATP-bound (B) or the ATP-free (F) transporter? Write down your answer as B or F. Hint: The ATP-bound transporter "faces outward."

F

Most eukaryotic ABC transporters are involved in exporting small molecules from the cytosol. In this subset of the ABC transporters, does the small molecule bind better to the ATP-bound (B) or the ATP-free (F) transporter?

F transporter

The family of ATPases is structurally related to the turbine-like pumps that acidify lysosomes and vesicles; however, they usually function in reverse, generating ATP from ADP and Pi using proton gradients across membranes. What are they called?

F-type pumps

DNA binding proteins generally recognize the minor groove of the target DNA

False

High degree of CpG methylation promotes gene transcription in eukaryotes

False

Each single neuron acts as a computational device. Typically, the magnitude of the combined postsynaptic potential is encoded in the...of firing of action potentials in the postsynaptic neuron

Frequency

Imagine a small synthetic vesicle made from pure phospholipids enclosing an interior lumen containing 1 mM glucose and 1 mM sodium chloride. If the vesicle is placed in pure water, which of the following happens faster?

H2O diffused in

eukaryotic nucleosome. (TF)

Histone H3 is a core histone, Histone H1 links two nucleosomes, Modification of histone tails play an important role in gene expression

The membrane potential in a particular hyperpolarized cell is measured to be -70 mV. For each of the following channels in this cell, the calculated Nernst equilibrium potential for the corresponding ion is presented. Indicate whether each channel is driven to pass the ion into (I) or out of (O) the cell. Your answer would be a four-letter string composed of letters I and O only, e.g. IIII. ( ) K+ channel; the K+ equilibrium potential is -60 mV. ( ) Na+ channel; the Na+ equilibrium potential is +70 mV. ( ) Ca2+ channel; the Ca2+ equilibrium potential is +130 mV. ( ) Cl- channel; the Cl- equilibrium potential is -90 mV.

IIII

Based on the graph, which of the following describes the effect of cocaine on the kinetics of dopamine reuptake by the transporter?

In the presence of cocaine, the material rate of transport (Vmax) is unaffected, but the apparent affinity of the transporter for dopamine is reduced

A neuron's repetitive firing rate is limited by an absolute refractory period, during which a new action potential cannot be generated. Which event is chiefly responsible for this limit?

Inactivation of voltage-gated Na+ channels

The lactose permease in E. coli is an H+ - lactose symporter that mediates the inward active transport of lactose if this sugar is present in the environment instead of glucose. Which of the following is true about this transporter?

Is has a twofold pseudosymmetrical structure

Sanshool is a natural compound found in Sichuan pepper, which is commonly used in making spicy Asian food, and creates a numbing sensation in the mouth. It is known to inhibit a subset....How do you think sanshool affects these sensory neurons?

It elevates the resting potential (to less negative values) and makes it easier to excite the neurons

MscS and MscL are mechanosensitive channels that...

Open in response to membrane tension

Indicate whether each of the following descriptions matches an ABC transporter (A), a P-type pump (P), or a V-type pump (V). Your answer would be a five-letter string composed of letters A, P, and V only

P. The pumps in the family are phosphorylated at a key Asp residue in each transport cycle A. This family is the largest among membrane transport proteins and includes some channels as well as pumps V. The pumps in this family are responsible for the acidification of synaptic vesicles P. The sodium-potassium pump is a member of this family A. The multi drug resistance protein is a member of this family

Indicate whether each of the following descriptions matches an ABC transporter (A), a P-type pump (P), or a V-type pump (V). Your answer would be a five-letter string composed of letters A, P, and V only, e.g. PPVVV. ( ) The pumps in this family are phosphorylated at a key Asp residue in each transport cycle. ( ) This family is the largest among membrane transport proteins and includes some channels as well as pumps. ( ) The pumps in this family are responsible for the acidification of synaptic vesicles. ( ) The sodium-potassium pump is a member of this family. ( ) The multidrug resistance protein is a member of this family

PAVPA

For which of the following ions is the intracellular concentration typically higher than the extra cellar concentration?

Potassium

Indicate true (T) and false (F) statements below regarding ion channels in cellular membranes. Your answer would be a four-letter string composed of letters T and F only, e.g. TTTT. ( ) With patch-clamp recordings, it is possible to study ion transport through a single molecule of a channel protein. ( ) Cells that are not electrically excitable often lack gated ion channels in their plasma membrane. ( ) The aggregate current crossing a patch of plasma membrane represents the degree to which each individual channel is open at that time. ( ) Patch-clamp recordings have shown that any voltage-gated ion channel opens as soon as the membrane potential is altered

TFFF

This large and complex general transcription factor has a DNA helicase activity that exposes the template for RNA polymerase II transcription. It also has a kinase activity that phosphorylates the C- terminal domain of the polymerase on Ser5 leading to promoter clearance. It is...

TFIIH

this large and complex general transcription factor has a DNA helicase activity that exposes the template for RNA polymerase II transcription. It also has a kinase activity that phosphorylates the C-terminal domain of the polymerase on Ser5 leading to promote clearance. It is called..

TFIIH

Many amino acids in our diet are absorbed via the transcellular transport pathway by the intestinal epithelial cells. This process requires ATP hydrolysis by...

The Na+ -K+ pumps in the basal and lateral domains of the plasma membrane

Which of the following is the reason why an aquaporin does not pass ions through?

The Na+ ions do not favorably interact with the wall of the pore and therefore cannot be dehydrated

A potassium channel conducts K+ ions several orders of magnitude better than Na+ ions, because...

The Na+ ions is too small to interact with the channel in a way that facilitates the loss of water from the ion

Aquaporin has a pair of key asparagine residues located on the wall almost halfway though its pore. These residues simultaneously bind to the oxygen atom of a passing water molecule, rendering it unavailable

The channel cannot conduct protons

Which of the following is a pump that hydrolyzes two ATP molecules per transport cycle?

The multi drug resistance protein

If the extracellular concentration of sodium ions is artificially decreased for a neuron...

The resting potential hardly changes but the action potential peak is lowered

Which of the following is NOT common between long-term potentiation and long-term depression?

They both result result in an enhanced postsynaptic response

cAMP binds a regulatory protein to activate transcription

True

Which of the following is true regarding genomic imprinting? a) It is an epigenetic phenomenon. b) It occurs in most animals. c) It always involves inactivation of genes through direct DNA methylation. d)It can "unmask" recessive alleles but cannot "mask" dominant ones. e) All of the above.

a) It is an epigenetic phenomenon. feedback: Genomic imprinting, observed in placental mammals and some flowering plants, is an epigenetic form of inheritance. It is mediated through DNA methylation in mammals, but it does not always involve gene inactivation by direct methylation. It can unmask recessive alleles or mask dominant alleles.

In analysis using two-dimensional gel electrophoresis of the proteins expressed in different cell types, the number of spots that are different in different cells usually exceeds the number of common spots, and even the common spots can still have different intensities. The spots representing which of the following proteins would you expect to be among the common spots when compared across several cell types? a) RPL10 (a ribosomal protein) b) HBA1 (a hemoglobin subunit) c) insulin (a hormone) d) tyrosine aminotransferase (a metabolic enzyme) e) all of the above

a) RPL10 (a ribosomal protein) feedback: Ubiquitously expressed gene products include ribosomal proteins, DNA and RNA polymerases, and DNA repair enzymes, among others.

The Trp operon in Escherichia coli encodes the components necessary for tryptophan biosynthesis. In the presence of the amino acid in a bacterium, ... a) the tryptophan operator is bound to the tryptophan repressor. b) the tryptophan repressor is bound to bacterial RNA polymerase. c) the expression of the tryptophan repressor is shut off. d) the operon genes are expressed. e) All of the above.

a) the tryptophan operator is bound to the tryptophan repressor. feedback: When tryptophan is present, it binds to the repressor which then binds to the operator to turn off the operon.

At the replication fork, the template for the lagging strand is thought to loop around. This looping would allow the lagging-strand polymerase to move along with the rest of the replication fork instead of in the opposite direction. The single-strand part of the loop is bound by the single-strand DNA-binding (SSB) proteins. As each Okazaki fragment is synthesized toward completion, how does the size of the loop change? What about the size of the SSB-bound part of the loop? a. Increases; increases. b. Increases; decreases. c. Decreases; increases. d. Decreases; decreases. e. Decreases; does not change.

a. Increases; increases.

The eukaryotic chromosomes are organized inside the nucleus with a huge compaction ratio of several-thousand-fold. What is responsible for such a tight packaging? a. The various chromatin proteins that wrap and fold the DNA b. The nuclear envelope which encapsulates the chromosomes c. The nuclear matrix that provides a firm scaffold d. All of the above

a. The various chromatin proteins that wrap and fold the DNA

What do the enzymes topoisomerase I and topoisomerase II have in common? a. They both have nuclease activity. b. They both create double-strand DNA breaks. c. They both require ATP hydrolysis for their function. d. They both can create winding (tension) in an initially relaxed DNA molecule. e. All of the above.

a. They both have nuclease activity.

The genetic information carried by a cell is passed on, generation after generation, with astonishing fidelity. However, genomes are still altered over evolutionary time scales, and even their overall size can change significantly. Which of the following genome-altering events has increased the size of the mammalian genome the most? a. Transposition b. Point mutation c. Chromosomal deletion d. Chromosomal inversion e. Chromosomal translocation

a. Transposition

The telomerase enzyme in human cells ... a. has an RNA component. b. extends the telomeres by its RNA polymerase activity. c. polymerizes the telomeric DNA sequences without using any template. d. removes telomeric DNA from the ends of the chromosomes. e. creates the "end-replication" problem.

a. has an RNA component.

several mechanisms contribute to the diversity of the mRNAa and proteins encoded by a single gene in our genome. Which is normally not one of them?

alternative choice of the reading frames

Under which of the following conditions is the Lac operon in Escherichia coli fully turned on? a) Low glucose and lactose levels b) Low glucose but high lactose levels c) High glucose but low lactose levels d) High glucose and lactose levels e) Low cAMP and high glucose levels

b) Low glucose but high lactose levels feedback: The Lac operon is fully turned on when glucose is absent AND lactose is present.

Transcription regulation has similarities and differences in bacteria and in eukaryotes. Which of the following is correct in this regard? a) Most bacterial genes are regulated individually, whereas most eukaryotic genes are regulated in clusters. b) The rate of transcription for a eukaryotic gene can vary in a much wider range than for a bacterial gene (which is, at most, only about 1000-fold). c) DNA looping for gene regulation is the rule in bacteria but the exception in eukaryotes. d) Transcription regulators in both bacteria and eukaryotes usually bind directly to RNA polymerase. e) The default state of both bacterial and eukaryotic genomes is transcriptionally active.

b) The rate of transcription for a eukaryotic gene can vary in a much wider range than for a bacterial gene (which is, at most, only about 1000-fold). feedback: Variation in transcription rates across the genome is much greater in eukaryotic cells (about one million-fold) compared to prokaryotic cells (about one thousand-fold). In eukaryotes, genes are often transcribed and regulated individually, and DNA looping occurs in the regulation of nearly every gene. In these cells, transcription regulators often assemble in groups and do not directly contact RNA polymerases. The default state of most eukaryotic DNA packaged into nucleosomes is off.

Protein subunits that interact specifically with DNA sequences ... a) typically recognize sequences of two to three nucleotide pairs in length. b) do so via hydrogen bonds, ionic bonds, and hydrophobic interactions. c) typically form about five weak interactions at the protein-DNA interface. d) often bind loosely to DNA. e) All of the above.

b) do so via hydrogen bonds, ionic bonds, and hydrophobic interactions. feedback: DNA-binding proteins typically recognize specific sequences that are 5 to 10 nucleotide pairs in length. This involves forming 20 or so weak interactions at the interface, including hydrogen-bonding, ionic bonding, and hydrophobic interactions. The sum of all protein-DNA interactions can result in high affinity and specificity.

You have engineered the X chromosomes in female mice such that one X chromosome expresses green fluorescent protein when active, while the other expresses red fluorescent protein. You have used these mice to study cancer in females. You know that each tumor is a clonal cellular proliferation, meaning all of its proliferating cells are descendants of a single original cancer-causing cell. It follows that, unless X-chromosome inactivation is perturbed in tumors, ... a) all tumor cells in one mouse should express the same fluorescent protein (either red or green), but tumor cells from different mice can show either red or green fluorescence. b) the cells in any tumor should all express the same fluorescent protein (either red or green), but independently derived tumors in the same mouse can show either green or red fluorescence. c) different cells within each tumor can express different fluorescent proteins, and the tumors would therefore show yellow fluorescence, but each cell shows either red or green fluorescence. d) each cell can express both fluorescent proteins and would therefore emit yellow fluorescence, and the tumors would glow in yellow as well. e) different tumors would show red, yellow, or green fluorescence.

b) the cells in any tumor should all express the same fluorescent protein (either red or green), but independently derived tumors in the same mouse can show either green or red fluorescence. feedback: Since different cells in the female body have randomly inactivated one or the other X chromosome, tumors derived from them will inherit the inactivation pattern and can therefore express one or the other fluorescent protein. However, all cells within each tumor are expected to express the same fluorescent protein.

Consider a cis-regulatory enhancer sequence in the Escherichia coli chromosome that is located thousands of nucleotide pairs upstream of the gene that it regulates. If the regulatory sequence is mutated to become nonfunctional, the introduction of the wild-type enhancer on a plasmid fails to regulate the gene. This implies that ... a) the regulatory sequence encodes a regulatory protein that binds near the promoter of the target gene and controls RNA polymerase binding. b) the regulation of the target gene involves looping out of the intervening DNA, and the promoter of the cis-regulatory sequence must be on the same chromosome. c) the regulatory sequence can bind directly to the RNA polymerase. d) the regulatory sequence cannot bind to a protein.

b) the regulation of the target gene involves looping out of the intervening DNA, and the promoter of the cis-regulatory sequence must be on the same chromosome. feedback: DNA looping can occur during bacterial gene regulation, where the intervening DNA acts as a tether to enormously increase the probability that the proteins bound near the promoter and those bound to the cis-regulatory sequences will collide with each other. This effect requires that both sequences be on the same DNA molecule, or be somehow linked physically.

Studying the expression of a transcription regulatory protein in two cell types, you have performed experiments showing that the mRNA encoding the protein is present at comparable levels in the cytosol of both cell types. However, based on the expression of its target genes, you suspect that the protein activity might be significantly different in the two cell types. Which of the following steps in expression of the gene encoding this protein is more likely to be differentially controlled in these cell types? a) transcription b) translation c) mRNA transport d) mRNA degradation

b) translation feedback: Since the mRNA levels are similar in both cell types, difference in protein activity can be attributed to differences in translation or in post-translational control.

In assembling a nucleosome, normally the ...(1) histone dimers first combine to form a tetramer, which then further combines with two ... (2) histone dimers to form the octamer. a. 1: H1-H3; 2: H2A-H2B b. 1: H3-H4; 2: H2A-H2B c. 1: H2A-H2B; 2: H1-H3 d. 1: H2A-H2B; 2: H3-H4 e. 1: H1-H2; 2: H3-H4

b. 1: H3-H4; 2: H2A-H2B

The mutation rate in bacteria is about 3 nucleotide changes per 10 billion nucleotides per cell generation. Under laboratory conditions, bacteria such as Escherichia coli can divide and double in number about every 40 minutes. If a single Escherichia coli cell is allowed to exponentially divide for 10 hours in this manner, how many mutations would you expect to observe on average in the genome (4.5 million nucleotide pairs) of each of the resulting bacteria compared to the original cell? Assume all mutations are neutral; that is, they do not affect the cell-division time. a. Less than 0.001 b. About 0.02 c. One or two d. About 10 e. About 100

b. About 0.02

Chromosome 3 contains nearly 200 million nucleotide pairs of our genome. If this DNA molecule could be laid end to end, how long would it be? The distance between neighboring base pairs in DNA is typically around 0.34 nm. a. About 7 mm b. About 7 cm c. About 70 cm d. About 7 m e. None of the above

b. About 7 cm

This protein folds into a doughnut shape that can encircle DNA. It can load on the DNA only when the DNA is broken in both strands, so that the DNA can thread through the hole in the protein. Which of the following proteins do you think matches this description? a. PCNA, the sliding clamp for DNA polymerases at the replication forks b. Ku, the protein that recognizes DNA ends and can initiate nonhomologous end joining c. MCM, the helicase critical for the initiation and elongation of replication d. Topoisomerase II, which can create or relax superhelical tension in DNA e. RecA/Rad51, which carries out strand invasion in homologous recombination

b. Ku, the protein that recognizes DNA ends and can initiate nonhomologous end joining

Which of the following is correct regarding the mutation rate of genomic DNA in different organisms? a. Human cells have a much higher mutation rate compared to bacteria when the rate is normalized to a single round of replication over the same length of DNA. b. Mutation rates limit the number of essential genes in an organism's genome. c. Mutations in the somatic cells cannot be lethal. d. Even if the mutation rate was 10 times higher than its current value, germ-cell stability in humans would not have been affected. e. All of the above.

b. Mutation rates limit the number of essential genes in an organism's genome.

In which phases of the eukaryotic cell cycle does homologous recombination often occur to repair DNA damage? a. G1 and S phases b. S and G2 phases c. G2 and M phases d. M and G1 phases e. G1 and G2 phases

b. S and G2 phases

During DNA replication in the cell, DNA primase makes short primers that are then extended by the replicative DNA polymerases. These primers ... a. are made up of DNA. b. generally have a higher number of mutations compared to their neighboring DNA. c. are made more frequently in the leading strand than the lagging strand. d. are joined to the neighboring DNA by DNA ligase. e. provide a 3′-phosphate group for the DNA polymerases to extend.

b. generally have a higher number of mutations compared to their neighboring DNA.

It has been shown that inhibition of a key chromatin remodeling complex known as NuRD, by deleting one of its subunits, can result in a significant increase in the efficiency of reprogramming of somatic cells into pluripotent stem cells. The reprogramming is normally done by the induced expression of a battery of transcription factors in the somatic cells, but is typically not very efficient. Such an observation suggests that the NuRD complex is normally involved in ... a. erasing the epigenetic memory in somatic cells. b. maintaining the epigenetic memory in somatic cells. c. preventing DNA replication. d. formation of extended loops from chromosome territories.

b. maintaining the epigenetic memory in somatic cells.

This general transcription factor recognizes the TATA box in RNA polymerase II promoters. It is...

ble to introduce a rather sharp kink in the double helix upon binding to DNA.

which of the following features is common between the replication origins in escheria coli and saccharomyces cerevisae?

both contain sequences that attract initiator proteins, as well as stretches of DNA rich in A-T base pairs

what is a function or characteristic of initiation factors that is common in both bacteria and euakryotes

bring first tRNA to the P site on a small subunit of ribosome

What would you expect to happen to the pattern of reporter expression in flies that lack the gene encoding Giant? a) It would be expressed in all seven stripes. b) It would be expressed in stripe 5 only. c) It would expand to cover a broad anterior region of the embryo. d) It would fail to express efficiently in the stripe 2 region. e) It would be expressed throughout the whole embryo.

c) It would expand to cover a broad anterior region of the embryo. feedback: As expected, lack of Giant or Krüppel results in a broad expression pattern for the second stripe.

Which of the following features is common between the replication origins in Escherichia coli and Saccharomyces cerevisiae? a. They both normally exist in one copy per genome. b. Both are specified by DNA sequences of tens of thousands of nucleotide pairs. c. Both contain sequences that attract initiator proteins, as well as stretches of DNA rich in A-T base pairs. d. Both contain GATC repeats that are methylated to prevent the inappropriate "firing" of the origin. e. All of the above.

c. Both contain sequences that attract initiator proteins, as well as stretches of DNA rich in A-T base pairs.

This protein is present at every replication fork and prevents DNA polymerase from dissociating, but does not impede the rapid movement of the enzyme. Which of the following is true regarding this protein? a. It self-assembles onto DNA at the replication fork. b. It is assembled on DNA as soon as DNA polymerase runs into a double-strand region of DNA. c. Its assembly normally follows the synthesis of a new primer by the DNA primase. d. It disassembles from DNA as soon as DNA polymerase runs into a double-strand region. e. All of the above.

c. Its assembly normally follows the synthesis of a new primer by the DNA primase.

Which of the following correlates the best with biological complexity in eukaryotes? a. Number of genes per chromosome b. Number of chromosomes c. Number of genes d. Genome size (number of nucleotide pairs)

c. Number of genes

Imagine a chromosome translocation event that brings a gene encoding a histone acetyl transferase enzyme from its original chromosomal location to a new one near heterochromatin. Which of the following scenarios is definitely NOT going to happen? a. The gene gets silenced due to heterochromatin expansion, leading to the misregulation of gene expression for a number of critical genes. b. The translocation event also brings along a chromatin barrier that can prevent heterochromatin expansion into the gene, and there is no phenotypic anomaly. c. Since the gene encodes a histone acetyl transferase, it resists heterochromatin expansion by acetylating its own histones. d. The level of the gene product decreases due to a position effect, leading to an imbalance in the chromatin state of the cell that results in the activation of programmed cell death.

c. Since the gene encodes a histone acetyl transferase, it resists heterochromatin expansion by acetylating its own histones.

Which of the following features of DNA underlies its simple replication procedure? a. The fact that it is composed of only four different types of bases b. The antiparallel arrangement of the double helix c. The complementary relationship in the double helix d. The fact that there is a major groove and a minor groove in the double helix

c. The complementary relationship in the double helix

What are the products of deamination of cytosine and 5-methyl cytosine, respectively? a. Thymine and uracil b. Thymine in both cases c. Uracil and thymine d. Uracil in both cases e. Xanthine and hypoxanthine

c. Uracil and thymine

During DNA replication, the single-strand DNA-binding (SSB) proteins ... a. are generally found more on the leading strand than the lagging strand. b. bind cooperatively to single-stranded DNA and cover the bases to prevent base-pairing. c. prevent the folding of the single-stranded DNA. d. bind cooperatively to short hairpin helices that readily form in the single-stranded DNA. e. All of the above.

c. prevent the folding of the single-stranded DNA.

binding of tryptophan to the Trp repressor protein results in

conformational change in repressor that allows the repressor to bind to operator

What would you expect to happen to the pattern of reporter expression in flies that lack the gene encoding Bicoid? a) It would be expressed in all seven stripes. b) It would be expressed in stripe 5 only. c) It would expand to cover a broad anterior region of the embryo. d) It would fail to express efficiently in the stripe 2 region. e) It would be expressed throughout the whole embryo.

d) It would fail to express efficiently in the stripe 2 region. feedback: As expected, lack of Bicoid or Hunchback results in an inefficient expression of the second stripe.

Two copies of the gene A exist in a diploid mammal. However, only one copy is expressed in every somatic cell. Different somatic cells in the body of each organism have inactivated one or the other allele in a seemingly random fashion, but when they divide, the daughter cells inherit the choice of the inactive allele faithfully. This is an example of ... a) X-inactivation b) Genomic imprinting c) Loss of heterozygosity d) Monoallelic gene expression e) Alternative gene splicing

d) Monoallelic gene expression feedback: Monoallelic expression can result from genomic imprinting, but not all examples of monoallelic expression are due to imprinting.

A gene that had been turned off in a liver cell has just been induced to be highly expressed as the cell responds to a new metabolic load. What observations do you expect to accompany this change? a. More than 100 proteins would become associated with the gene for its transcription. b. The nuclear position of the gene would change to place it in a "transcription factory." c. Chromatin modifications associated with the gene would change in favor of higher expression. d. All of the above.

d. All of the above.

DNA glycosylases constitute an enzyme family found in all three domains of life. They can ... a. add sugar moieties to DNA. b. remove sugar moieties from DNA. c. add a purine or pyrimidine base to DNA. d. remove a purine or pyrimidine base from DNA. e. remove a nucleotide from DNA.

d. remove a purine or pyrimidine base from DNA.

Steroid hormones act in transcription regulation by:

displacing inhibitor proteins from transcription factors

enzyme that catalyzes the initial processing of miRNA in the nucleus

drosha

Which of the following is directed by transcription activators in eukaryotic cells in order to provide a more accessible DNA for the transcription machinery? a) Nucleosome remodeling b) Histone removal c) Histone replacement d) Histone modifications e) All of the above

e) All of the above feedback: Eukaryotic transcription activator proteins can direct local alterations in chromatin structure. This can be achieved through covalent histone modifications, nucleosome remodeling or removal, and histone replacement.

What determines the time and place that a certain gene is transcribed in the cell? a) The type of cis-regulatory sequences associated with it b) The relative position of cis-regulatory sequences associated with it c) The arrangement of various cis-regulatory sequences associated with it d) The specific combination of transcription regulators present in the nucleus e) All of the above

e) All of the above feedback: The expression of a gene can be determined by its cis-regulatory sequences and transcription regulators that function in trans.

Which of the following DNA-binding motifs uses β sheets to recognize DNA bases? a) The helix-turn-helix motif b) The leucine zipper c) The zinc finger motif d) The helix-loop-helix motif e) None of the above

e) None of the above feedback: All of the examples presented in A to D use α helices to interact with DNA. A limited number of DNA-binding motifs use β sheets to recognize DNA bases.

DNA ligases are used in both DNA replication and repair to seal breaks in the DNA. But DNA damage can result in single- or double-strand breaks that are not normal ligase substrates. These need to be processed first before a ligase can act on them. One of the enzymes that is recruited to some of such breaks is called PNK. It has two separate activities on the DNA, both of which can help provide a canonical ligase substrate. Which of the following activities would you expect PNK to have in this context? a. 5′ kinase (phosphorylation of a free 5′-OH group) and 3′ kinase b. 5′ phosphatase (dephosphorylation to create a free 5′-OH group) and 3′ phosphatase c. 3′ kinase and 3′ phosphatase d. 5′ phosphatase and 3′ kinase e. 5′ kinase and 3′ phosphatase

e. 5′ kinase and 3′ phosphatase

Nucleosomes that are positioned like beads on a string over a region of DNA can interact to form higher orders of chromatin structure. Which of the following factors can contribute to the formation of the 30-nm chromatin fiber from these nucleosomes? a. Interactions that involve the histone tails of neighboring nucleosomes b. Interaction of the linker histone H1 with each nucleosome c. Binding of proteins to DNA or the histones d. ATP-dependent function of chromatin remodeling complexes e. All of the above

e. All of the above

On average, errors occur in DNA synthesis only once in every ten billion nucleotides incorporated. Which of the following does NOT contribute to this high fidelity of DNA synthesis? a. Complementary base-pairing between the nucleotides b. "Tightening" of the DNA polymerase enzyme around its active site to ensure correct pairing before monomer incorporation c. Exonucleolytic proofreading by the 3′-to-5′ exonuclease activity of the enzyme to correct mispairing even after monomer incorporation d. A strand-directed mismatch repair system that detects and resolves mismatches soon after DNA replication e. All of the above mechanisms DO contribute to the fidelity.

e. All of the above mechanisms DO contribute to the fidelity.

The chromatin remodeling complexes play an important role in chromatin regulation in the nucleus. They ... a. can slide nucleosomes on DNA. b. have ATPase activity. c. interact with histone chaperones. d. can remove or exchange core histone subunits. e. All of the above.

e. All of the above.

Upon heavy damage to the cell's DNA, the normal replicative DNA polymerases may stall when encountering damaged DNA, triggering the use of backup translesion polymerases. These backup polymerases ... a. lack 3′-to-5′ exonucleolytic proofreading activity. b. are replaced by the replicative polymerases after adding only a few nucleotides. c. can create mutations even on undamaged DNA. d. may recognize specific DNA damage and add the appropriate nucleotide to restore the original sequence. e. All of the above.

e. All of the above.

Most fish genomes are at least 1 billion nucleotide pairs long. However, the genome of the puffer fish Fugu rubripes is quite small at only about 0.4 billion nucleotide pairs, even though the number of Fugu genes is estimated to be comparable to that of its relatives which have larger genomes. What do you think mainly accounts for the Fugu genome being this small? a. Evolutionary advantage of extremely small exon sizes in the Fugu lineage b. Unusual disappearance of all intronic sequences from the Fugu genome c. Increased abundance of transposable elements in the Fugu genome d. Increased occurrence of mitotic whole-chromosome loss in the Fugu lineage e. Low relative rate of DNA addition compared to DNA loss in the Fugu lineage

e. Low relative rate of DNA addition compared to DNA loss in the Fugu lineage

Compared to the human genome, the genome of yeast typically has ... a. more repetitive DNA. b. longer genes. c. more introns. d. longer chromosomes. e. a higher fraction of coding DNA.

e. a higher fraction of coding DNA.

The nuclear DNA polymerases in human cells ... a. polymerize about 1000 nucleotides per second during DNA replication in vivo. b. are incapable of 3′-to-5′ exonuclease activity. c. are capable of 3′-to-5′ DNA polymerase activity. d. have a single active site that is used for both polymerization and editing. e. are unable to initiate polymerization de novo (i.e. in the absence of a primer).

e. are unable to initiate polymerization de novo (i.e. in the absence of a primer).

the function of the rev protein encoded by the HIV genome is to

ensure that HIV gene transcripts containing introns are transported to the cytoplasm

coactivators are

factors that bind to other proteins, not to DNA directly

as a general rule, eukaryotic mRNAs have a shorter half life compared to bacterial mRNAS (T/F)

false

Each single neuron acts as a computational device. Typically, the magnitude of the combined postsynaptic potential is encoded in the ... of firing of action potentials in the postsynaptic neuron.

frequency

during DNA replication in the cell, DNA primase makes short primers that are extended by the replicative DNA polymerases. These primers..

generally have a higher number of mutations compared to their neighboring...

Attenuation at the trp operon in E. coli occurs when

high tryptophan levels allow the formation of a terminator stem-loop in the trpL mRNA

eukaryotic pre-RNAs undergo a number of modifications such as capping the 5' end. A 5' cap...

is identical for all mRNA that are transcribed by RNA polymerase II

Carboxy Terminal Domain of RNA polymerase II:

it is phosphorylated by TFIIH, splicing and polyadenylation factors bind when it is phosphorylated,

some viruses encode a protease that cleaves the translation initiation factor eIF4G. rendering it unable to bind to eIF4E. What is the consequence of this cleavage?

it shuts down most host cell protein synthesis and diverts the translation machinery to IRES-dependent initiation thus favoring viral protein synthesis

under which of the following conditions is the Lac operon in Escheria Coli turned on?

low glucose but high lactose

the transcript for which of the following noncoding RNA in our cells is expected to undergo 5' cap addition after transcription?

miR-21 (a microRNA)

DNA glycosylases constitute an enzyme family found in all three domains of life. They can,

remove a purine or pyrimidine base from DNA

Histone deacetylases act to:

remove covalent modifications on the lysine residues of histones

Which RNA polymerase component is required for promoter recognition in prokaryotes?

sigma

Co-activators and co-repressors affect the function of an activator/repressor. They generally are:

small molecules

what non-coding RNA chiefly functions in the processing a chemical modification or ribosomal RNA (rRNAs)?

small nucleolar RNA (snoRNA)

as an mRNA molecules is processed in the nucleus, it loses some proteins and binds to new ones, some of which are used in mRNA surveillance pathways. The presence of which of the following molecules on an mRNA is a signal that the mRNA is still not ready for nuclear transport?

snRNPs used in splicing

what statement about the Lac operon is true?

the binding of the lac repressor to the operator is not affected by the presence of glucose

which of the following features of DNA is a basis for replication?

the complimentary relationship in the double helix

DNA and RNA polymerase differ in all of the following except:

the type of chemical reaction they catalyze

in different regions of the chromosome, the ratio of histone H1 to histone H2A may vary, but the ratio of H2A to histone H2B is generally the same. If the amount of H1 increases in a region of chromatin, what will be its effect on compaction of the DNA and transcription in that region?

transcription in that region will decrease

which of the following is a corepressor in negative regulation of Trp operon?

tryptophan

The following are DNA binding domains used in transcription factors:

zinc finger, helix-turn-helix, leucine zipper helix loop helix