The effectiveness of allosteric effectors in regulating metabolic pathways is based on their ability to
(A) change the conformation of the target enzyme(s)
(B) alter the concentration of the target enzyme(s)
(C) denature the target enzyme(s)
(D) interfere with competitive inhibitors.
Ribulose 1,5-bisphosphate carboxylase, which catalyzes the fixation of carbon dioxide during photosynthesis in plants and many algae, is located in which of the following cellular compartments?
The phospholipids of plasma membranes routinely exhibit which of the following forms of movement?
Diffusion in the plane of the bilayer
Translocation from one side of the bilayer
to the other side
Rotation of fatty-acid residues around
saturated carbon atoms
(A) I only
(B) II only
(C) III only
(D) I and III only
Of the following, the best evidence that the interaction between a protein and a nucleic acid in a particular complex is hydrophobic is if the complex is dissociated by
(A) high salt
(B) organic solvents
(C) treatment with a nuclease (D) treatment with a protease
Excitation in the postsynaptic membrane is caused by which of the following?
(A) Increased sodium permeability
(B) Increased potassium permeability
(C) Decreased acetylcholine permeability (D) Decreased calcium permeability
Mutation of DNA within a single somatic cell of a multicellular organism
(A) may have no phenotypic consequence (B) is usually inherited by individuals
in future generations
(C) automatically results in cell death
(D) is generally deleterious to the organism
DNA photolyase recognizes which of the following in order to repair pyrimidine dimers?
(A) The distortion in the double helix
(B) A specific palindromic sequence
(C) Three hydrogen bonds between affected
(D) A specific origin for repair to initiate
Which of the following is present in double- stranded cDNA but absent in the corresponding genomic DNA?
(A) A homopolymeric sequence of A:T base pairs (B) Promoter sequences
(C) Intron sequences
(D) 5¢ and 3¢ untranslated sequences
Which of the following molecular genetic techniques is used to identify protein-protein interactions?
(A) Yeast two-hybrid system
(B) Southern hybridization analysis
(C) Polymerase chain reaction (PCR)
(D) Fluorescence in situ hybridization (FISH)
Which of the following enzymes would prevent religation of a restriction enzyme–digested plasmid?
(A) Klenow fragment of DNA polymerase I (B) Calf intestine phosphatase
(C) T4 DNA ligase
(D) AMV reverse transcriptase
(E) Taq DNA polymerase
Which of the following molecules forms extracellular cross-linked fibrils of great tensile strength?
(B) Fibronectin (C) Laminin
Which of the following statements is correct concerning cell locomotion?
(A) The amount of F-actin continues to increase as the cell moves.
(B) Actin polymerizes at the leading edge. (C) Actin is synthesized at the leading edge. (D) Myosin contraction pushes actin
filaments to the leading edge.
(E) New membrane is synthesized at the
A wild-type E. coli strain was isolated from a local pond. After cultivation in the laboratory, cell-free culture medium from the strain was
incubated with an arg- auxotrophic lab strain. Arg+ colonies were readily isolated following
the incubation. The lab strain produced no prototrophs when incubated alone. Which of the following is most likely responsible for the arg+ colonies obtained in the experiment?
(A) An F¢ plasmid
(B) Reversion of the arg- mutation (C) An ampR plasmid
(D) A transducing phage
(E) A transposon
In humans, maturing oocytes progress to metaphase of meiosis II and then arrest their development until fertilization. Which of the following would NOT be true of meiosis II–arrested oocytes?
(A) The oocytes are haploid.
(B) Homologous chromosome pairs
(C) Sister chromatids have separated. (D) Chromosomes are condensed. (E) Chromosomesarealignedat
the spindle midplane.
For the equilibrium above, which of the following statements most accurately describes what occurs when the pH is increased (becomes more basic) ?
(A) The equilibrium constant Keq increases.
(B) The equilibrium constant Keq decreases.
(C) A new equilibrium is established that favors the reactants.
(D) A new equilibrium is established that favors the products. (E) Thepositionoftheequilibriumremainsthesame.
The most definitive method for determining if actin is a component of an isolated membrane preparation would be to analyze the membrane proteins by
(A) thin-layer chromatography
(B) polyacrylamide gel electrophoresis
(C) column chromatography
(E) W estern blot (immunoblot)
Which of the following sequences correctly portrays the flow of electrons during photosynthesis?
(A) NADPH Æ O2 Æ CO2
(B) NADPH Æ chlorophyll Æ Calvin cycle (C) NADPH Æ electron transport chain Æ O2 (D) H2O Æ photosystem I Æ photosystem II (E) H2OÆNADPHÆCalvincycle
Which of the following statements does NOT explain how viruses often produce more proteins than would be predicted from the size of their genome?
(A) Overlapping open reading frames are found on opposite strands.
(B) Some of the proteins are cleavage products of other functional proteins.
(C) Some mRNA molecules are translated in two different frames.
(D) Some primary transcripts are spliced to yield different mRNAs.
(E) Several proteins are posttranslationally fused to make a chimeric protein.
In C. elegans, the P6p cell in the lateral hypodermis is normally adjacent to the anchor cell and divides three times to form part of the vulva. The anchor cell itself is not part of the vulva and does not divide. If P6p is destroyed, the adjacent P5p cell will divide three times and form the part of the vulva that P6p normally forms. However, if the anchor cell is destroyed, no cell forms the vulva. Which of the following statements best explains these results?
(A) The anchor cell inhibits P6p from forming a vulva.
(B) The anchor cell induces P6p to form a vulva.
(C) P6p inhibits the anchor cell from forming a vulva.
(D) P6p induces the anchor cell to form a vulva. (E) P5p induces P6p to form a vulva.
A high-frequency burst of action potentials causes a change in the surface of the presynaptic membrane described as ruffling. Which of the following is the cause of the change?
(A) Elevation of the osmotic pressure in the synaptic cleft
(B) Electrically induced membrane breakdown (C) Growth-cone extensions toward new
(D) Inability of endocytosis to keep pace with
(E) Cytosolic acidification triggered by K+ efflux
Packaging of concatemeric lambda DNA into phage heads involves cleavage of the DNA at which of the following sites?
(A) cos (B) nutR (C) EcoRI (D) attP (E) PL
All of the following are associated with vertebrate promoters located in active chromatin EXCEPT
(A) acetylated histones
(B) DNase I–hypersensitive sites
(C) methylated cytosine bases
(D) bound TFIID
A human female is heterozygous for the sex- linked genetic disease glucose-6-phosphate dehydrogenase (G6PD) deficiency. Half of her cells have normal levels of the G6PD enzyme and the other half have extremely low levels. This pattern of expression is an example of which of the following?
(A) Codominance (B) Linkage
(C) Mosaicism (D) Polymorphism (E) Epistasis
Just before sperm addition, sea urchin eggs are microinjected with a calcium chelator. What event will most likely NOT take place after fertilization?
(A) Depolarization of the plasma membrane (B) Elevation of protein kinase C activity (C) Elevation of phospholipase C activity (D) Cortical granule exocytosis
When Lucifer yellow, a small dye, is injected into a neuron of the retina, neighboring neurons become rapidly labeled. If the retina is incubated in dopamine prior to Lucifer yellow injection, only the injected neuron becomes labeled. These findings suggest which of the following?
Neurons of the retina communicate via gap junctions.
Dopamine is transferred between cells via gap junctions.
Dopamine decreases the permeability of gap junctions.
(A) I only
(B) II only
(C) III only
(D) I and II only (E) IandIIIonly
The force between methylamine (CH3NH4+) and
acetate (CH3COO-) will be greater in methanol than in water because
(A) methanol, but not water, is structurally similar to methylamine
(B) methanol has a lower dielectric constant than water
(C) acetate and methylamine are more soluble in methanol than in water
(D) dipole-dipole interactions between acetate and methylamine are induced in methanol, but not in water
(E) methylgroupinteractionsarefavoredin methanol
In glycoproteins, the carbohydrate moiety always gets attached through which of the following amino acids?
(A) Glycine or alanine
(B) Glutamine or arginine
(C) Aspartate or glutamate
(D) Tryptophan or phenylalanine (E) Asparagine, serine, or threonine
Individuals with a rare genetic condition accrue abnormally high levels of DNA damage from x-ray-induced double-strand breaks. The inability to repair such breaks would be expected to result in which of the following?
(A) Accumulation of mucopolysaccharides in connective tissue
(B) Inability to remove UV-induced thymine dimers
(C) Irreversible loss of a cell cycle checkpoint and thus overproliferation
(D) Loss of apoptotic mechanisms, resulting in loss of appropriate cell death
(E) Increased frequency of sister chromatid exchange and chromosome breakage
Fluorescent tubulin is microinjected into the cytoplasm of a mammalian cell in interphase. Which of the following best describes where the fluorescent tubulin will first be incorporated?
(A) In the nucleus
(B) In the centromeres
(C) Throughout the length of the existing
(D) At the distal tips of microtubules (E) Attheplusendsofmicrofilaments
Which of the following chromosomal changes is NOT responsible for position-effect variegation of a gene?
(A) Transposition (B) Translocation (C) Inversion
(D) Polyploidization (E) Deletion
Deletion of the TATA box from a eukaryotic promoter for gene X results in which of the following?
(A) The general transcription factors will not be able to bind to their specific DNA sequences.
(B) A gene-specific activator will not be able to bind to its regulatory DNA sequence.
(C) Transcription of the gene will be unaffected by the mutation.
(D) RNA polymerase will not transcribe genes downstream of gene X.
(E) The transcripts for gene X will lack a 5¢ cap.
An enzyme has a Vmax of 50 mmol product formed (minute ¥ mg protein)-1 and a Km of 10 mM for
the substrate. When a reaction mixture contains the enzyme and 5 mM substrate, which of the following percentages of the maximum velocity will be closest to the initial reaction rate?
(A) 5% (B) 15% (C) 33% (D) 50% (E) 66%
Which of the following best explains why the plasma membranes of all cells exhibit a negative resting potential?
(A) The membrane is mostly permeable to Cl-,
and the Cl- gradient favors its diffusion
out of the cell.
(B) The membrane is mostly permeable to K+,
and the K+ gradient favors its diffusion into
(C) The membrane is mostly permeable to K+,
and the K+ gradient favors its diffusion out
of the cell.
(D) The membrane is mostly permeable to Na+,
and the Na+ gradient favors its diffusion
into the cell.
and the Na+ gradient favors its diffusion out of the cell.
Extracellular matrices are LEAST likely to play a major role in which of the following?
(A) Enabling tissues to resist compression and tension
(B) Giving tissues elasticity
(C) Keeping cell layers separated from
(D) Promoting the diffusion of oxygen
G-protein linked receptors exhibit which of the following?
(A) Tyrosine kinase activity
(B) ATPase activity
(C) Seven transmembrane domains (D) Nuclear localization
Which is LEAST likely to be involved in the expression of mammalian immunoglobulin genes?
(A) Gene amplification
(B) DNA rearrangements to produce new
antibody variable regions
(C) Transcription factors expressed only
in antibody-producing cells
(D) Deletion of some chromosomal DNA
Which of the following is true regarding the acetylation of histones during transcription?
(A) Histone acetyltransferases are part of the general transcription factor complex.
(B) Histones are acetylated immediately after translation in the Golgi apparatus.
(C) Acetylation of local histones further increases the overall positive charge in that region.
(D) H1 acetylation results in transcriptional silencing.
(E) Depositionofacetylatedhistonesis regulated by histone phosphorylation.
In the prototype bacterial two-component regulatory system, which of the following are true?
Induced gene expression requires cell-to-cell contact.
The sensor molecule is often a surface receptor.
The activator protein is transcriptionally induced.
The activator protein undergoes a conformational change.
(A) I and II only
(B) II and III only (C) II and IV only (D) I, II, and III only (E) I, II, and IV only
The pha-4 gene encodes a developmental transcription factor involved in pharynx development. Early in development, low
levels of PHA-4 protein are observed, while later in development, high levels of PHA-4 protein are present. Early targets of PHA-4 regulation encode regional specifiers, while later targets are required for the structure and function of the pharynx. Which of the following is the most likely explanation for this observation?
(A) The PHA-4 protein must have a different primarystructureearlyindevelopment as compared to later development.
(B) The early target genes activate the expression of the late target genes.
(C) The early target genes repress the expression of the late target genes.
(D) The PHA-4 binding sites of the early targets have a low affinity for the PHA-4 protein, while the late targets have a higher affinity.
(E) ThePHA-4bindingsitesoftheearlytargets have a high affinity for the PHA-4 protein, while the late targets have a lower affinity.
In E. coli, deleting the ribosome binding site and region 1 of the trp attenuator and leaving the remainder of the attenuator intact has which of the following effects?
(A) The attenuator structure will not form, and the structural genes will be transcribed.
(B) The attenuator structure will always form, and transcription will terminate.
(C) The frequency of attenuation will still be controlled by the concentration of trp-tRNAtrp.
(D) Attenuation will occur randomly.
The end result of the kinase cascade activated by epidermal growth factor (EGF) is
(A) activation of transcription factors
(B) transphosphorylation of the EGF receptor (C) receptor internalization
(D) activation of Ras
subunits of its G protein
During protein synthesis, which of the following proteins interacts via its N-terminal sequence with the signal recognition particle (SRP) ?
(A) Nuclear matrix protein (B) Lysosomal protein
(C) Peroxisomal protein (D) Mitochondrial protein (E) Chloroplastprotein
Which of the following is LEAST soluble in aqueous solution?
(D) Palmitic acid (E) Oxaloaceticacid
Within the aqueous environment of an animal cell, sugars are stored as polymers rather than as monomers. If the sugars were stored as monomers instead of polymers, which of
the following properties would be LEAST affected?
(A) Freezing point (B) Boiling point
(C) Osmotic pressure (D) Viscosity
The series of reactions given above are
at equilibrium. The formation of T can be increased by an increase in the concentration of all of the following EXCEPT
(A) M (B) N (C) O (D) Q (E) S
72.Ifthereaction A+BÆC isfirstorderwith respect to A and first order with respect to B, then the rate equation for the forward reaction would be
(A) rate = k[A] (B) rate = k[B] (C) rate = k[A][B] (D) rate=kA +kB
In a series of two-factor crosses, 30 percent recombination occurs between gene A and
gene B, and 26 percent recombination between gene B and gene C. If the order of genes on the chromosome is A-B-C, how much recombination will be seen between A and C in a two-factor cross?
(A) 4% (B) 8% (C) 28% (D) 50% (E) 56%
A LOD score is used to do which of the following?
(A) Evaluate the linkage of a phenotypic character to a particular region on a chromosome
(B) Determine the order of markers in a linkage group
(C) Estimate the penetrance of an allele (D) Evaluate the extent of epistatic
interaction between two genetic loci (E) Estimatethefrequencyofdouble
A phenotypically wild-type fruit fly (Drosophila melanogaster) was crossed with a fly of unknown genotype. Of the progeny, 3/8 were wild-type; 3/8 had vestigial wings and wild-type bodies;
1/8 had wild-type wings and black bodies; and 1/8 had vestigial wings and black bodies. The allele for vestigial wings is vg, and the allele for black body is b. What were the genotypes of the two parent flies?
(A) vg/vg ; b/b and vg/+ ; b/+ (B) vg/+ ; +/+ and vg/+ ; b/b (C) vg/vg;+/+andvg/+;b/+ (D) vg/vg ; b/+ and vg/+ ; b/+ (E) vg/+;b/+andvg/+;b/+
Five mutants of a fungus that are auxotrophs for compound X have been isolated. A complementation test is performed on these mutants by mating them in all possible pairwise combinations and testing the progeny for prototrophy. Based on the results above, which of the following is correct? (A plus sign [+] indicates that the progeny of the cross are prototrophs, while a minus sign [-] indicates they are auxotrophs.)
(A) All of the mutants belong to one complementation group.
(B) Mutant 1 forms one complementation group, while mutants 2, 3, 4, and 5 form another.
(C) Mutant 1 forms one complementation group; mutants 2 and 4 form a second complementation group; and
mutants 3 and 5 form a third group.
(D) Mutant 1 forms one complementation group; mutants 2 and 4 form a second; mutant 3 forms a third; and
mutant 5 forms the fourth complementation group.
11.During DNA replication in bacteria, the mismatch repair system differentiates the daughter strand from the parent strand by
(A) methylated adenine in the sequence GATC in the parent strand but not the daughter strand (B) methylated adenine in the sequence GATC in the daughter strand but not the parent strand
(C) DNA polymerase bound to the parent strand but not the daughter strand
(D) a stretch of single-stranded DNA on the parent strand but not the daughter strand
(E) a DNA helicase bound to the parent strand but not the daughter strand
12.Tetanus toxin is taken up by receptor-mediated endocytosis at the termini of axons and is moved by retrograde transport to the neuronal cell body. Treating neurons with microtubule depolymerizing drugs blocks the transport. Which of the following treatments would also be likely to block the transport?
(A) Injecting the neurons with RNAi directed against dynein
(B) Injecting the neurons with kinesin I (C) Injecting the neurons with an antibody
directed against myosin V
(D) Overexpressing a dominant negative rho
in the neurons
13.Protein modifications occurring in the Golgi include which of the following?
(A) Removal of sialic acid
(B) BiP-mediated protein folding (C) Removal of the signal peptide (D) Attachment of core N-linked
complex N-linked oligosaccharides
14.Translocation of most proteins into the ER requires all of the following EXCEPT
(A) a signal sequence
(B) a signal receptor protein (C) ribosomes
15.A genetic analysis of an unknown infectious agent reveals that it contains only the nucleotides G, A, U, and C in the proportion 30 percent, 35 percent, 15 percent, and 20 percent, respectively. Based
on this information, this infectious agent is most likely a
(A) double-stranded DNA virus
(B) double-stranded RNA virus
(C) single-stranded DNA virus
(D) single-stranded RNA virus
(E) virus containing a DNA/RNA hybrid
17.The most likely amino acid that would yield the above titration curve would be
(B) Glutamic acid (C) Glycine
The technique of chromosome painting in the analysis of human karyotypes relies on which of the following?
(A) Inherent fluorescence due to G-C base pairs (B) Inherent fluorescence due to A-T base pairs (C) Specific hybridization with fluorescent probe
(D) Restriction digestion followed by nick
translation with fluorescent nucleotides (E) Fluorescence resonance energy transfer
18.Which of the following is the origin of the majority of the ATP used in the pathway of gluconeogenesis?
(A) b-oxidation of fatty acids
(B) Breakdown of amino acids
(C) Degradation of glycogen
(D) Oxidation of fructose-6-phosphate (E) Fructose-2,6-bisphosphate
19.Which of the following enzymes would be most useful as a marker for chloroplasts during isolation of plant cell organelles?
(A) Malate dehydrogenase (B) Phosphoribulokinase (C) DNA polymerase
20.Which of the following best indicates that a segment of DNA is a gene?
(A) Multiple expressed sequence tags (ESTs) of the DNA sequence
(B) Multiple short overlapping reading frames (C) A 50% sequence identity with a known
(D) A DNA sequence that is predicted to be able
to form a large hairpin loop
21.Which of the following events, occurring within a tandem repeat sequence, will cause an expansion or contraction of the array?
(B) Homologous recombination (C) Unequal crossing-over
(D) Error-prone DNA repair (E) Inversion
Each repeat unit within the nuclear ribosomal gene cluster of eukaryotes (rDNA) contains
(A) a promoter for RNA pol I (B) a terminator for RNA pol II (C) an A TG start codon
(D) polyadenylation signals
(E) at least one tRNA gene
90. Which is NOT a characteristic typical of retrotransposons?
(A) Encoding a reverse transcriptase
(B) Constituting a significant proportion
of animal genomes
(C) Random integration in genome (D) Flanking by direct repeats
(E) Alternative splicing
22.The unfolded protein response involves all of the following EXCEPT
(A) the chaperonin BiP
(B) the proteasome
(C) the sec61p translocon
(D) attenuation of protein synthesis (E) attenuation of mRNA synthesis
23.Proteasomes are responsible for the degradation of all of the following EXCEPT
(A) cyclin B during anaphase
(B) securin at anaphase
(C) proteins targeted to lysosomes
(D) foreign protein for antigen presentation
(E) misfolded proteins from the ER
24.The coding region of a gene is 102 nucleotides long, including both start and stop codons. Which of the following would be the most likely effect of a single nucleotide deletion at position 76 in the coding region?
(A) There would be no effect on the polypeptide. (B) Only the active site would be affected.
(C) The entire amino acid sequence of the
polypeptide would change.
(D) There would be changes in only the first
25 amino acids.
8 amino acids.
A eukaryotic translation complex during the elongation stage is represented by the diagram above. Which of the following labels on the diagram is NOT correct?
(A) Location of the mRNA cap structure (B) Direction of ribosome movement (C) Anticodon of a tRNA molecule
(D) 5¢ end of a tRNA molecule
(E) Carboxyl-terminusofthegrowing peptide chain
29.An altered form of a replicative DNA polymerase lacks 3¢ Æ 5¢ exonuclease activity. This alteration
would most likely result in which of the following?
(A) A decrease in processivity
(B) An increased mutation rate
(C) An ability to replicate DNA without a primer (D) An inability to replicate DNA
30.Glycine can be formed from another amino acid in a single step. This reaction is catalyzed by
(B) glycine cleavage enzyme
(C) glycine aminotransferase
(D) serine dehydratase
When 50 mL of a 14C sample is added into 10 mL of scintillation cocktail, a liquid scintillation counter reports 15,200 counts per minute (cpm), with an efficiency of 0.92. Which of the following is closest to the number of disintegrations per minute (dpm) in the 50 mL sample?
(A) 1,520 dpm B. 13,984 dpm B.16,522 dpm C.21,000 dpm
Glucagon stimulates release of fatty acids from adipocytes because it
(A) activates a transporter of fatty acids (B) activates lipoprotein lipase
(C) activates hormone-sensitive lipase (D) inhibits export of glycerol
When a polymerase chain reaction (PCR) amplification was performed on human genomic DNA, multiple products of varying sizes were obtained, including one of the expected size. Which of the following modifications to the protocol is the most likely to eliminate the extra PCR products?
(A) Raising the denaturation temperature from 94∞Cto96∞C
(B) Raising the annealing temperature from 52∞C to 56∞C
(C) Raising the elongation temperature from 70∞C to 74∞C
(D) Increasing the elongation time from 3 minutes to 4 minutes
(E) Decreasingthenumberofcyclesfrom 30 to 24
A cell-free translation system contains microsomes but lacks signal recognition particles (SRP). The mRNA encoding a secretory protein is translated in this system. Which of the following outcomes is most likely?
(A) No protein synthesis will occur.
(B) Protein synthesis will begin but the protein
will not be fully synthesized.
(C) The protein will be fully synthesized and
its signal sequence will be removed. (D) The protein will be fully synthesized and
incorporated into microsomes.
not incorporated into microsomes.
31.A mixture of soluble proteins containing proteins X and Y is immunoprecipitated using anti–protein X antibody. Both protein X and protein Y are immunoprecipitated. Which of the following does NOT explain this observation?
(A) Protein X and protein Y are part of the same multimeric complex.
(B) Protein X and protein Y are covalently bound.
(C) Protein Y is a truncated version of protein X.
(D) Protein X and protein Y are present in the same organelle.
(E) Anti–protein X antibodies cross-react with protein Y.
32.In contrast to chemical-induced mutations, mutations induced by transposons are more likely to
(A) be lethal
(B) be dominant
(C) be stable
(D) revert to wild type (E) be a gain of function
33.Matrix-assisted laser desorption ionization time of flight (MALDI-TOF) spectrometry is most useful for predicting which of the following?
(A) Molecular mass
(B) Isoelectric point
(C) Bonding patterns
(D) Secondary structure
35.In the diagram shown above, segments A and C are copies of a repeated DNA sequence, flanking a unique stretch shown as B. A and C are in
an inverted orientation relative to each other,
as indicated by the arrows. Intramolecular recombination between segments A and C would most likely lead to
(A) duplication of segment B only
(B) duplication of segments A, B, and C (C) inversion of segment B
(D) deletion of segment B only
(E) deletion of segments A, B, and C
Elongation of telomeres by the enzyme telomerase and the processing of pre-mRNA to mRNA by the spliceosome share which of the following characteristics?
(A) Both processes require double-stranded DNA for enzyme function.
(B) Both processes occur primarily in the cytoplasm.
(C) Both processes require G-proteins and downstream effectors.
(D) Both processes require protease activity and are processive.
(E) Both processes require an RNA component for enzyme function.
Questions 110-112 refer to the following.
(A) Klenow fragment (B) b clamp
(D) SSB protein
(E) RNase H
42.Proofreads as part of its catalytic activity
43.Maintains the parental strands as single strands of DNA
44.Increases the processivity of DNA polymerase
Questions 113-116 refer to the following.
(A) Diacylglycerol (DAG)
(B) Heteromeric G protein (hetG)
(C) Phosphatidyl 1,4,5-triphosphate (IP3)
(D) Adenylate cyclase (AC) (E) PhospholipaseC(PLC)
114.Produces cAMP when activated
115.Inactivated by GTPase-activating proteins (GAPs)
116.Directly stimulates the release of calcium from intracellular stores
Questions 117-119 refer to the following.
(B) Hydrolysis (C) Group transfer (D) Isomerization (E) Oxidation
45.Cleavage of a peptide bond
46.Phosphorylation of a serine residue on a protein
47.Formation of a disulfide bond between cysteines
Questions 120-122 refer to the following stages of the cell cycle.
(A) Interphase (B) Prophase (C) Metaphase (D) Anaphase (E) Cytokinesis
118.Kinetochores are paired and possess microtubules of equal length.
119.Microtubule depolymerization is essential.
Questions 123-126 refer to the following.
(A) Ribulose 1,5-bisphosphate carboxylase (B) Arginase
(D) Malate dehydrogenase
(E) 5-phosphoribosyl l-pyrophosphate synthase
48.A metallo-enzyme that catalyzes the conversion of molecular nitrogen to two molecules of ammonia
49.A key regulatory enzyme in the Calvin cycle
50.An enzyme whose product serves as a precursor for the biosynthesis of both purine and pyrimidine nucleotides
51.Anenzymeintheureacyclewhoseproduct is urea
Questions 127-128 refer to the following.
(A) ChIP (chromatin immunoprecipitation) (B) RNAi
120.Used to analyze proteins associated with specific DNA sequences
121.Used to alter the expression of specific genes in eukaryotic cells
Questions 129-131 refer to the following amino acids.
(A) Proline (B) Tyrosine (C) Histidine (D) L ysine (E) Isoleucine
52.The amino acid that would contribute most to protein absorption at 280 nm
53.The amino acid that would be expected to be located within the interior of a folded protein suspended in an aqueous buffer
54.The amino acid that would disrupt the ordered structure of a folded a-helix
Questions 132-135 refer to the following.
(A) Zinc finger
(B) Acidic domain
(C) Triple helix
(D) Long terminal repeat (L TR) (E) Stem-loop
122.A common structural motif found in the DNA binding domains of transcriptional activators
123.A retroviral sequence element
124.A structural motif in transcriptional activator proteins that interacts with proteins in the general transcription apparatus
125.The structure of a transcriptional attenuator
A cell line is transfected with a plasmid encoding either a secreted glycoprotein, X, or a variant of X that contains the amino acids KDEL at its C terminus, both of them under control of an inducible promoter. KDEL motifs are normally found on proteins located in the lumen of the ER. At 30 minutes after induction, cycloheximide, an inhibitor of protein synthesis, is added to the culture medium. At 30, 45, and 60 minutes after induction (that is, 0, 15, or 30 min in cycloheximide), the cells are lysed, rough microsomes are isolated and solubilized, and X or X-KDEL is immunoprecipitated from the solubilized material and run on SDS-PAGE gels.
The following gels are obtained.
The most likely reason why there is less material in lanes 2 and 3 than there is in lane 1 is that protein X
(A) is digested in cycloheximide
(B) is less stable than protein X-KDEL (C) is translocated into the lumen of the
endoplasmic reticulum within
15 minutes of its synthesis (D) exits the endoplasmic reticulum
within 15 minutes of its synthesis (E) isincorporatedintoCOPIvesicles
within 15 minutes of its synthesis
The most likely explanation for the additional bands seen in lanes 5 and 6 is that
(A) the signal sequence is not removed from some of the X-KDEL molecules
(B) X-KDEL oligomerizes after protein synthesis is completed
(C) X-KDEL becomes modified in the endoplasmic reticulum after protein synthesis is completed
(D) some of the X-KDEL molecules are modifiedintheGolgiandthenreturned to the endoplasmic reticulum
(E) thequalitycontrolmechanisminthe endoplasmic reticulum recognizes X-KDEL as being aberrant and has targeted it for degradation
If cycloheximide had been omitted from the experiment, then
(A) no protein band would be observed in lane 2 (B) bands at higher molecular weight equivalent
to those observed in lanes 5 and 6 would
be observed in lanes 2 and 3
(C) only the lower-molecular-weight bands
would be observed in lanes 5 and 6 (D) the total amount of protein observed in
each gel lane would increase
lanes 2 and 3 and 5 and 6 would increase
A series of chemical compounds have properties that suggest they would interfere with chloroplast function.
The effects of the compounds have been tested using illuminated suspensions of isolated chloroplasts and measuring the rates of ATP synthesis and O2 production. The results are shown below with the arrow indicating time of
addition of the compound.
Which of the following statements is true for the chloroplasts treated with compound A?
(A) No proton gradient exists across the thylakoid membrane, and the reduction of NADP+ drops to zero.
(B) No proton gradient exists across the thylakoid membrane, but the reduction of NADP+ continues at the initial rate.
(C) The proton gradient across the thylakoid membrane is unaffected, but the reduction of NADP+ drops to zero.
(D) No proton gradient exists across the thylakoid membrane, but the reduction of NADP+ increases to a new, higher steady-state level.
(E) Neithertheprotongradientacrossthe thylakoid membrane nor the reduction of NADP+ is affected.
55.Which of the following compounds appear(s) to act by blocking noncyclic photophosphorylation while leaving cyclic photophosphorylation unaffected?
(A) Compound A only (B) Compound B only (C) Compound C only (D) Compounds A and B (E) CompoundsBandC
56.Isolated chloroplast suspensions can be induced to make ATP in the dark for a short period by incubating them in a low-pH solution and then rapidly transferring them to a high-pH solution. Ifsubjectedtosuchaprocedure,chloroplasts would be expected to make ATP if they were first treated with which of the following compounds?
(A) A only
(B) B only
(C) C only
(D) A and B only (E) BandConly
To understand the signaling pathway leading from sperm-egg fusion to calcium increase, various substances were injected into sea urchin eggs. The effects of these substances on calcium increase are shown in the table below.
58.Calcium increase at fertilization requires which of the following?
II. Tyrosine kinase
(A) I only (B) II only (C) III only (D) I and III (E) IIandIII
59.A reasonable explanation for the calcium increase shown in line 7 of the table is that
(A) IP3 must be dephosphorylated
(B) phosphatase activity is required
(C) wild-type SHP2 phosphorylates PLCg (D) PLCg cannot be dephosphorylated
60.An informative experiment to determine the position of PLCg in the signaling pathway would be to inject eggs with which of the following?
(A) Dominant-negative PLCg protein and IP3 (B) Wild-type PLCg only
(C) Wild-type PLCg and IP3
(D) A calcium chelator only
61.Based on the information provided, which of the following pairs is in the correct order to lead to calcium increase in the normal signal transduction pathway induced by fertilization?
Wild-type flies of the species Drosophila melanogaster have red eyes and wings with normal cross veins. Recessive mutant alleles of the sex-linked genes w (white) and cv (crossveinless) lead, respectively, to the formation of white eyes and crossveinless wings.
A virgin female fly who was heterozygous for the mutant w and cv alleles was crossed to a wild-type male. The male progeny of this cross were primarily of two types. One type had white eyes and normal wings and the other had red eyes and crossveinless wings. Smaller numbers of wild-type males and males with white eyes and crossveinless wings were also obtained.
146. The occurrence of the wild-type male progeny was most likely the result of
(A) dominance of the wild-type alleles of the w and cv genes
(B) independent assortment of the w and cv genes during meiosis
(C) crossing over in the female parent (D) crossing over in both parents
62.Approximately 6 percent of the male progeny were mutant for both phenotypes. Thus, the
w and cv genes are separated by approximately how many map units?
(A) 3 (B) 6 (C) 12 (D) 24 (E) 44
63.The percent of phenotypically wild-type females from this cross is predicted to be approximately
(A) 100% (B) 50% (C) 25% (D) 12% (E) 6%
Lactate dehydrogenase (LDH) can exist as various tetrameric isozymes. Extracts from different rat tissues were run on a nondenaturing polyacrylamide gel and stained for LDH activity, as shown below. Standard tetramers of M subunits (M4) and H subunits
(H4) were run alongside the tissue extracts.
65.Which of the following is the subunit composition of the isozyme running at position 2 ?
(A) M4 (B) M3H (C) M2H2 (D) MH3 (E) H4
66.Which of the following conclusions can be drawn from the experiment regarding the heart isozymes?
(A) All of the enzyme exists in the H4 isozyme form.
(B) Only heart tissue contains the H4 form.
(C) Heart tissue contains all five isozymes. (D) The M4 form is lacking in heart tissue.
(E) Hearttissueistheonlytissuethatdoes not contain all possible combinations.