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Cell Bio????

Terms in this set (116)

Which of the following sequences of events occurs when E. coli are released from catabolite repression by transfer from high glucose to low glucose medium

A. cAMP levels rise, cAMP binds to CRP, cAMP-CRP complex binds to a site on DNA and activates transcription
B. cAMP levels rise, cAMP binds to CRP, cAMP-CRP complex binds to a site on DNA and represses transcription
C. cAMP levels rise, cAMP binds to CRP, cAMP-CRP complex is removed from site on DNA and activates transcription
D. cAMP levels fall, cAMP is removed from CRP, CRP binds to a site on DNA and activates transcription
E. cAMP levels fall, cAMP is removed from CRP, CRP binds to a site on DNA and represses transcription
A. cAMP levels rise, cAMP binds to CRP, cAMP-CRP complex binds to a site on DNA and activates transcription
Heat-shock proteins were originally described as proteins produced in response to heat stress. Some are now known to act as

A. molecular chaperone proteins that regulate protein folding
B. protein tyrosine kinases
C. proteases that degrade ubiquitin-tagged proteins
D. GTPase activating proteins
E. ionophores that dissipate H+ gradients
A. molecular chaperone proteins that regulate protein folding
In a bacterial cell, a mutation in an aminoacyl-tRNA synthetase leads to charging of the entire tRNA ser population with alanine. Which of the following describes the result of using these aminoacyl tRNAs for protein synthesis

A. the alanyl-tRNA will not function in protein synthesis
B. proteins synthesized will contain neither alanine nor serine
C. proteins synthesized will contain only serine where alanine would normally occur
D. proteins synthesized will contain only alanine where serine would normally occur
E. proteins synthesized will randomly contain either alanine or serine where serine would normally occur
D. proteins synthesized will contain only alanine where serine would normally occur
A secretory protein found in the blood has a molecular weight of 30kD, but when the same protein is translated from mRNA by purified ribosomes, aminoacyl tRNA, GTP and elongation factors in the test tube, its MW is 32kD. This difference most likely results because the protein synthesized in the test tube

A. suffered random mutations during synthesis
B. still contained the signal peptide
C. was not released from the ribosome/mRNA complex
D. did not interact with the ribosomes
E. was synthesized from D isomer amino acids instead of L isomer
B. still contained the signal peptide
Which of the following is NOT true concerning the peptidyl transferase activity of the ribosome

A. it is a ribozyme, having catalytic activity
B. it catalyzes peptide bond formation
C. it moves the ribosome down the mRNA, so translation can proceed
D. it is associated with the large ribosomal subunit
E. it does not require any direct additional energy, such as ATP hydrolysis to function
C. it moves the ribosome down the mRNA, so translation can proceed
A common event leading to the bleeding disorder hemophilia is the occurrence of a nonsense mutation in the gene for clotting factor VIII, secreted by the liver into the bloodstream and essential for clotting. This mutation leads to hemophilia because

A. the protein product cannot be completed
B. the protein product is altered at a single amino acid, destroying its function
C. intron splicing out of the mRNA is impaired
D. the gene is transcribed at reduced rates
E. the gene alteration results in a gain of function in the mutant protein
A. the protein product cannot be completed
In a hypoxic skeletal muscle cell, which of the following substances is not involved in continuation of ability to contract

A. myokinase
B. creatine kinase
C. creatine phosphate
D. acetyl CoA
E. phophoenol pyruvate
F. glucose-6-phosphate
D. acetyl CoA
Glial cells associated with phagocytosis to fight infection and remove debris are

A. microglia
B. oligodendrocytes
C. Schwann cells
D. myelin sheaths
E. astrocytes
F. interneurons
A. microglia
The structure of the axoneme of a cilium or flagellum is comprised of

A. 1 central microtubule and 9 outer microtubule doublets
B. a central pair of microtubules and 9 outer microtubules doublets
C. a central pair of microtubules and 9 outer single microtubules
D. a central pair of microfilaments and 9 outer microfilament doublets
E. a stator, bearing, hook, and flagellin propeller powered by PMF
B. a central pair of microtubules and 9 outer microtubules doublets
In relaxed muscle Ca++ is found in high concentration in the

A. sarcoplasm
B. T-tubules
C. sarcoplasmic reticulum
D. sarcolemma
E. neuromuscular junction
C. sarcoplasmic reticulum
Biochemical analysis of muscle contraction shows

A. myosin binds calcium
B. titin binds calcium
C. actin has ATPase activity
D. myosin has ATPase activity
E. actin and myosin both bind calcium and have ATPase activity
D. myosin has ATPase activity
Kinesin is a motor molecule that is characterized by

A. activation of sliding of flagellar microtubules
B. sliding along actin in the sarcomere
C. motion towards the + end of the microtubule
D. motion along intermediate filaments
E. motion towards the minus end of the microtubule
C. motion towards the + end of the microtubule
You genetically engineer a normally cytoplasmic protein to instead accumulate in the rough ER of yeast cells. To accomplish this goal, you need to

A. do nothing, as all proteins go through the rough ER
B. incorporate appropriate N-linked oligosaccharides (glycosylation)
C. incorporate a DNA sequence into the gene for a signal peptide and an ER retention signal (KDEL/HDEL)
D. incorporate a DNA sequence into the gene for a transit peptide and an ER retention signal (KDEL/HDEL)
E. incorporate appropriate lipid groups (prenylation)
C. incorporate a DNA sequence into the gene for a signal peptide and an ER retention signal (KDEL/HDEL)
The part of a neuron that carries nerve impulses toward the cell body is called

A. a nerve
B. an axon
C. a dendrite
D. a neurotransmitter
E. myelin
C. a dendrite
Ribosomes that do not anchor to the RER surface during translation most probably

A. are synthesizing cytoplasmic, mitochondrial, chloroplastic, nuclear, or peroxisome proteins
B. have a protein defect in the ribosome where it attaches to the RER surface
C. have a signal peptidase error
D. have and error in their TIM/TOM or TIC/TOC proteins
E. have a defect in their chaperone proteins
A. are synthesizing cytoplasmic, mitochondrial, chloroplastic, nuclear, or peroxisome proteins
The initial amino acid incorporated into a nascent peptide is N-formylated in

A. eukaryotic translation
B. prokaryotic transcription
C. prokaryotic translation
D. A and C
E. B and C
C. prokaryotic translation
eIFs are required for initiation in

A. E. coli translation
B. chaperonin activity
C. eukaryotic translation
D. eukaryotic transcription
E. DNA replication
C. eukaryotic translation
Shine-Dalgarno sequeces are present in

A. prokaryotic mRNA
B. prokaryotic rRNA
C. prokaryotic tRNA
D. eukaryotic mRNA
E. eukaryotic rRNA
F. eukaryotic tRNA
A. prokaryotic mRNA
Both intermolecular and intramolecular splicing results in the formation of the final protein from ___ as well as a (usually) discarded polypeptide product formed from the ___

A. exons; introns
B. introns; exons
C. exteins, inteins
D. inteins, exteins
E. none of the above
C. exteins, inteins
In eukaryotes gene amplification is well tolerated when the amplified DNA encodes for RNA final products, but generally is not tolerated well when the final product is a protein. Why might it be advantageous for a cell to amplify RNA producing genes but not protein producing ones

A. it allows for the manufacture of many RNA molecules when needed in the cell
B. many proteins may be amplified from a single mRNA molecule
C. more RNA is needed by the cell than protein
D. RNAs are amplified from a single protein molecule
E. A and B
E. A and B
Attenuation occurs at the trp operon in E. coli

A. when intracellular tryptophan levels are low
B. when regions 3 and 4 in the leader RNA pair to form a stem loop
C. as a result of the trp repressor binding to the trp operator
D. when a ribosome stalls at the tryptophan codons in region 1 of the leader RNA
E. none of the above
B. when regions 3 and 4 in the leader RNA pair to form a stem loop
A suppressor tRNA causes

A. the wrong amino acid to be inserted into a protein, totally abolishing protein function
B. premature termination because of an amino acid encoding codon being read as a stop codon
C. a single amino acid deletion in the final protein
D. a shift in the codon reading frame
E. normal termination because of an aberrant stop codon being read as an amino acid encoding codon.
E. normal termination because of an aberrant stop codon being read as an amino acid encoding codon.
Genes that are always "turned on" in a cell are referred to as

A. anabolic genes
B. mutations
C. constitutive genes
D. inducible genes
E. catabolic genes
F. regulated genes
C. constitutive genes
During the synthesis of secretory proteins on the rough ER, the signal recognition particle (SRP) binds to

A. the signal sequence
B. the signal recognition particle receptor
C. transit peptidase
D. both A and B
E. none of the above
D. both A and B
The Nernst equation can be used to calculate the resting membrane potential of a cell provided that

A. the membrane is impermeable to ions
B. the membrane is permeable to only a single ion
C. the membrane is permeable to both Na+ and K+
D. the membrane is permeable to Na+, K+, and Cl-
E. none of the above
B. the membrane is permeable to only a single ion
Directional movement in response to a chemical stimulus is referred to as

A. chemotaxis
B. chemotropism
C. chimerism
D. chemiosmosis
E. cholinergic response
F. none of the above
A. chemotaxis
Amoeboid movement is mediated by

A. dynein
B. actin and mysosin
C. PMF and flagellin
D. kinesin
E. cilia
B. actin and mysosin
Smooth muscle contraction is regulated by

A. direct neural stimulation of the motor end plates of smooth muscle cells
B. intracellular stores of Ca++
C. influx of extracellular Ca++
D. calmodulin
E. C and D
F. B and D
E. C and D
Once an amino acid has been attached to the appropriate tRNA, the tRNA is said to be ______ and amino acid is said to be ______

A. charged, activated
B. activated, energized
C. energized, activated
D. activated, charged
E. none of the above
A. charged, activated
Cardiac cell contraction

A. is regulated by the pacemaker region via gap junctions
B. is regulated by direct neural stimulation of the motor end plates of cardiac cells
C. is regulated by hormonal control of extracellular Ca++ influx
D. is regulate by creatine kinase
A. is regulated by the pacemaker region via gap junctions
In eukaryotes, one way integral membrane proteins differ from soluble proteins is

A. they are not made on ribosomes
B. they have several signal sequences
C. they have stop-transfer sequences
D. they do not require SRPs
E. they are made on smooth, not rough ER
C. they have stop-transfer sequences
The type of transcription factor responsible for regulating gene expression in response to steroids in animal systems is

A. helix-turn-helix
B. Zinc finger
C. Leucine zipper
D. helix-loop-helix
E. the CRP
F. none of the above
B. Zinc finger
Which of the following best characterizes the relative concentrations of the major cations in the cytosol of typical resting eukaryotic cells

A. high K+ low Na+ low Cl- high Ca++
B. high K+ low Na+ high Cl- low Ca++
C. low K+ high Na+ low Cl- low Ca++
D. low K+ high Na+ high Cl- high Ca++
E. high K+ low Na+ low Cl- low Ca++
F. low K+ low Na+ low Cl- low Ca++
E. high K+ low Na+ low Cl- low Ca++
The calcium pump or calcium ATPase

A. is responsible for removing calcium from the T tubule
B. increases the level of calcium in the axon terminal
C. is a passive transporter
D. removes calcium from the sarcoplasm
E. increases bone density
D. removes calcium from the sarcoplasm
the genes of the tryptophan operon

A. are each individually transcribed into monocistronic messages when tryptophan levels are low
B. code for enzymes involved in the degradation of tryptophan when tryptophan levels are high
C. are transcribed when the trp repressor binds to the trp operator
D. are transcribed when tryptophan binds directly to the trp operator
E. code for enzymes involved in sequential steps of tryptophan biosynthesis
E. code for enzymes involved in sequential steps of tryptophan biosynthesis
In the central nervous system, the myelin sheath is formed by

A. oligodendrocytes
B. Schwann cells
C. node of Ranvier
D. motor neurons
E. the axon
A. oligodendrocytes
Regulatory elements embedded in the DNA within 200 bp of the transcriptional start site are referred to as

A. proximal elements
B. distal elements
C. trans-acting factors
D. cis-acting elements
E. A and C
F. A and D
F. A and D
The molecular motor protein associated with eukaryotic ciliary and flagellar movement is
A. flagellin
B. myosin
C. Dynein
D. Kinesin
E. Actin
F. none of the above
C. Dynein
Peptide bond formation is
A. powered by the ATP used to initially "charge" the tRNA
B. catalyzed by ribozymes
C. catalyzed by ribosomal RNA
D. catalyzed by ribosomal proteins
E. A and B
F. A, B, and C
F. A, B, and C
A "nonsense" mutation causes
A. change in one amino acid
B. premature termination because of a stop codon
C. a single amino acid deletion in the final protein
D. a shift in the codon reading frame
E. a change in one amino acid to a chemically similar amino acid
B. premature termination because of a stop codon
The actin-activated ATPase of myosin II is known to be localized to the:
A. globular head
B. neck
C. tail
D. light chains
E. hinge
F. thin filaments
A. globular head
An enhancer region
A. can be located thousands of base pairs away from the transcription start site of the gene it controls
B. can be located within an intron of a gene
C. can be located downstream of the gene it regulates
D. A and B
E. A, B, and C
E. A, B, and C
In vertebrae genes, transcription regulatory regions that contain CpG islands are inactivated by which CpG modification?
A. Methylation
B. Myristylation
C. Phosphorylation
D. Acetylation
E. Ubiquitination
A. Methylation
The huge variety of VDJ region antibody products are produced by:
A. DNA rearrangement
B. alternative splicing
C. Exon shuffling
D. protein splicing
E. guide RNA editing of premRNA
A. DNA rearrangement
The initial methionine of a nascent polypeptide is N-formylated in
A. eukaryotic translation
B. prokaryotic transcription
C. prokaryotic translation
D. A and C
E. B and C
C. prokaryotic translation
Basal transcription factors
A. are necessary for transcription via RNA polymerase II
B. are sufficient for transcription via RNA polymerase II
C. assemble on CAAT and GC boxes
D. are referred to as distal elements
E. all of the above
F. none of the above
A. are necessary for transcription via RNA polymerase II
The glial cells responsible for generating the blood-brain barrier are
A. microglia
B. oligodendrocytes
C. Schwann cells
D. myelin sheaths
E. astrocytes
F. interneurons
E. astrocytes
To regulate gene expression in response to a particular steroid, the transcription factor must be able to
A. bind specific cis-acting steroid response elements upstream of the transcribed sequence
B. interact with basal transcription factors and RNA polymerase II to activate transcription
C. bind a specific steroid, thus acting as a receptor as well
D. all of the above
E. none of above, as steroids use a different mechanism
D. all of the above
The genes of the tryptophan operon
A. are each individually transcribed into monocistronic messages when tryptophan levels are low.
B. code of enzymes involved in the degradation of tryptophan when tryptophan levels are high
C. are transcribed when the trp repressor binds to the trp operator
D. are transcribed when tryptophan binds directly to the trp operator
E. code for enzymes involved in sequential steps of tryptophan biosynthesis
E. code for enzymes involved in sequential steps of tryptophan biosynthesis
A "missense" mutation causes
A. a change in one amino acid
B. premature termination because of a stop codon
C. a single amino acid deletion in the final protein
D. a shift in the codon reading frame
E. a change in one amino acid to a chemically similar amino acid
A. a change in one amino acid
Effector molecules
A. are associated with the induction of enzyme synthesis
B. are associated with repression of enzyme synthesis
C. induce conformational changes
D. are often small organic molecules
E. all of the above
E. all of the above
Gene regulation may occur
A. by methylation of DNA
B. by acetylation of histones
C. post-transcriptionally
D. by regulation of translation
E. all of above
F. none of above
E. all of above
When E. coli are grown on media that contain both glucose and lactose, the lac operon genes will not be expressed at high levels because
A. the lac repressor binds to the lac operator and inhibits transcription of the lac operon
B. the CRP protein binds to the lac promoter and inhibits transcription of the lac operon
C. the CRP protein is not bound to the lac promoter region due to low cAMP levels in the cell
D. synthesis of the mRNA is prematurely terminated as a result of attenuation
E. the question as stated is incorrect, because the lac operon will be expressed at high levels under the given conditions.
C. the CRP protein is not bound to the lac promoter region due to low cAMP levels in the cell
Describe prokaryotic mRNA translation in detail, including all steps from start to finish, including all factors.
Initiation: IF1 2 and 3 bind to 30s subunit. tRNA fmet and mRNA bind to the 30s. The shine-dalgarno sequence on the 5' mRNA is recognized by a 16s rRNA which helps it bind. IF1 and 3 dissociate. IF2 bound to GTP positions the tRNA fmet in the P site. GTP is hydrolyzed and IF2 dissociates. The 50s subunit binds

Elongation: the aminoacyl tRNA binds to the A site with the help of EF-Tu bound to GTP. GTP is hydrolyzed and EF-Tu is recycled by EF-Ts. A peptide bond forms between the carboxy-terminus of the amino acid on the peptidyl tRNA and the N-terminus of the newly added amino acid. EFG bound to GTP translocates the ribosome down to the next codon. The empty tRNA moves to the E site. The peptide chain bearing tRNA move to P site and A site is open to new tRNA

Termination: A protein binding factor recognizes a stop codon and releases the mRNA and then the complex dissociates.
Describe post-translational and co-translational transport
Co-translational: occurs in export/endomembrane proteins. 15-30 amino acids are translated and form a signal peptide. This is bound by a SRP that temporarily stops translation. The SRP binds to a translocon on the ER membrane. GTP binds the SRP and it places the signal through a protein pore. GTP hydrolyzes and SRP dissociates. Translation continues until it's complete. A signal peptidase cleaves the signal peptide. The protein undergoes modification and packing inside the ER.

Post-translational: occurs in nuclear, mitochondrial, and chloroplastic proteins. Transit peptide is translated on free-floating ribosome. Transit peptide receptor places peptide on contact site of organelle where inner and outer membrane are close. Chaperone proteins keep the peptide straight as its fed through the pore. Transit peptidase cleaves the transit peptide. Chaperones fold the protein
Describe the molecular events involved in regulation of the lac operon in response to both glucose and lactose levels.
Lac operon is an inducible operon of a catabolic pathway. Its repressor is usually active and bound to the operator. When levels of lactose rise, the repressor is bound by a lactose derivative (allolactose) which causes inactivation and dissociates from the operator due to a conformational change. Transcription is turned on and the encoded lactose degrading enzymes are produced (B-galactosidase). When glucose levels are high, even if lactose is high, transcription is not induced. This is because glucose is the more favorable energy store and if its available then lactose isn't used. Glucose inhibits adenylate cyclase, the enzyme that produces cAMP. cAMP normally binds to a CRP protein that binds to the DNA and promotes RNA polymerase attachment. In low levels of cAMP, the CRP protein is not bound and transcription isn't initiated (positive control)
Describe and compare how eukaryotic and prokaryotic flagella are constructed and function
Prokaryotic flagella are made up of flagellin protein while eukaryotic flagella are made up of tubulin. The movement of prokaryotic flagella is proton driven (PMF), whereas the movement of eukaryotic flagella is ATP driven. Prokaryotic flagella have rotator movement (clockwise or counterclockwise), whereas eukaryotic flagella have blending movement (more back and forth)

A flagellum composed of flagellin is attached to a hook. Then attached to a bearing in the outer membrane which is attached to a rod in the intermembrane space. Then comes the S ring and the M ring which are powered by PMF (proton motive force).

In eukaryotes the cilia/flagella are composed of tubulin. The microtubules are arranged in a circle of 9 doublets and 2 microtubules in the center. ATP hydrolysis causes the dynein proteins to move along the microtubule doublets. In flagella this contraction is asymmetric and causes the flagella/cilia to bend.
Completely describe transcript (mRNA) abundance regulation in the prokaryotic trp operon and discuss whether or not the attenuation mechanism of transcriptional regulation is appropriate for eukaryotes
The trp operon is a repressible operon that encodes the anabolic pathway that produces tryptophan. This operon is turned off by its own product which means that tryptophan is a corepressor. Tryptophan is bound by a repressor protein and the repressor protein is activated and binds to the trp operator region due to a conformational change created by the the corepressor binding. Negative control: transcription is blocked. When tryptophan is scarce, the trp operon is transcribed. When there is enough tryptophan, the whole trp operon is not transcribed, but the leader sequence is. Attenuation reduces the synthesis of a specific mRNA. Attenuation is not appropriate for eukaryotes because transcription and translation are not coupled. In prokaryotes, transcription and translation are coupled so this makes attenuation possible.
Describe the molecular events involved in skeletal muscle contraction following neurotransmitter release through complete muscular contraction, including energetic and regulatory elements and the cyclic actin/myosin process of skeletal muscle contraction.
Action potential in a motor neuron triggers the release of Ca2+ ions from the sarcoplasmic reticulum

Calcium ions bind to troponin (on actin) and cause tropomyosin to move, exposing binding sites for the myosin heads

The actin filaments and myosin heads form a cross-bridge that is broken by ATP

ATP hydrolysis causes the myosin heads to swivel and change orientation

Swiveled myosin heads bind to the actin filament before returning to their original conformation (releasing ADP + Pi)

The repositioning of the myosin heads move the actin filaments towards the center of the sarcomere

The sliding of actin along myosin therefore shortens the sarcomere, causing muscle contraction
Describe eukaryotic mRNA translation in detail, including all steps from start to finish, including all factors
Initiation:
eIF2 (bound to GTP) binds tRNAmet before tRNAmet binds to small (40S) subunit. Methionine not formylated.

eIF2-tRNAmet - 40S complex recognizes 5 ́ mRNA end cap & binds: no ribosome binding site on eukaryotic mRNA.

Complex slides down mRNA 5 ́ -> 3 ́ until it encounters 1st AUG plus some nucleotides on either side: ACCAUGG consensus start (Kozak sequence).

tRNA base-pairs with AUG, 60S (large subunit) ribosomal subunit binds, eIF2 detaches.

Elongation:
Successive amino acids added one by one from N terminus to C terminus: peptide bond formed between each & nascent chain by catalytic activity of 23S (28S in eukaryotic cytoplasm) rRNA.

Aminoacyl tRNAs now all come in at aminoacyl site: only one that enters at P site is start codon tRNAmet.

After start tRNAmet in place, next codon (3 ́ -ward) read by next aminoacyl tRNA.

Elongation factors EF-Tu & EF-Ts, driven by 2GTP -> 2GDP + 2Pi, help position aminoacyl tRNA, & EF-G translocates ribosome to next mRNA codon, also hydrolyzing GTP for energy.

Termination:
A protein release factor, not a tRNA, recognizes stop codon at end of coding region of mRNA.

Polypeptide chain released from terminal tRNA and complex dissociates.
How do siRNAs and microRNAs regulate gene expression?
microRNA controls gene expression mainly by binding with messenger RNA (mRNA) in the cell cytoplasm. Instead of being translated quickly into a protein, the marked mRNA will be either destroyed and its components recycled, or it will be preserved and translated later.

siRNAs silence certain gene expression by cleaving the mRNA molecules coding the target genes. ... This cleavage results in mRNA fragments that are further degraded by cellular exonucleases.
Describe in detail how a neural action potential is generated and propagated from a stimulus received via a dendrite to neurotransmitter release from the axon termini. Explain why this action potential can only travel unidirectionally in its passage down an axon towards the axon termini. Include all ion flow, channel opening, channel closing, and membrane potential events
...
How do riboswitches work?
Riboswitches are inhibitor proteins (Usually the end product of the pathway) which bind directly
to the mRNA and can cause the formation of terminator loops. Additionally, they can also prevent translation, since the inhibitor protein is bound to the mRNA
the ribosome won't bind to the strand of mRNA. Ex: The rib operon in B. subtilis is prevented when FMN (end product) binds to the riboswitch.
ATP levels in a muscle cell remain relatively constant up to complete exhaustion because of the action of

A. the ryanodine receptor
B. creatine kinase
C. myokinase
D. creatine
E. B, C, and D
F. none of the above
E. B, C, and D
The function of chaperone proteins is to

A. assist channel proteins in translocating nascent polypeptide strands into the ER
B. assist in proper protein folding
C. accompany the signal sequence binding protein
D. co-translocate growing nascent polypeptide strands during translation
E. none of the above
B. assist in proper protein folding
Dynein is a molecular motor protein associated with

A. actin filaments
B. intermediate filaments
C. microtubules
D. myosin filaments
C. microtubules
The most common step at which gene expression is regulated is

A. transcription elongation and termination
B. mRNA transport
C. translation initiation
D. transcription initiation
E. mRNA processing
D. transcription initiation
the type of transcription factor responsible for regulating gene expression of the lac operon in response to the presence or absence of lactose in bacteria is

A. helix-turn-helix
B. zinc finger
C. leucine zipper
D. helix-loop-helix
E. the CRP
F. none of the above
A. helix-turn-helix
Kinesin is a molecular motor protein associated with

A. actin filaments
B. intermediate filaments
C. microtubules
D myosin filaments
C. microtubules
Which one of the following statements about a transcriptional promotor is false

A. in mammals and fruit flies, the promoter consists of two separate DNA sequences know as the -10 and -35 regions
B. the promoter is involved in recruiting RNA polymerase to the DNA
C. the promoter is involved in specifying the direction of transcription by RNA polymerase
D. In E. coli the promoter is recognized by the sigma subunit of RNA polymerase
E. the promoter is located near the transcription start site of a gene
A. in mammals and fruit flies, the promoter consists of two separate DNA sequences know as the -10 and -35 regions
When tryptophan levels are low in wild type E. coli

A. the trp repressor will have tryptophan bound to it
B. the trp repressor will bind to the trp operator
C. the trp repressor will not bind to the trp operator because the sequence of the operator becomes altered by targeted mutagenesis
D. the trp repressor will not bind to the trp operator because the recognition helices of the protein are not the proper distance apart to fit into the adjacent major grooves of the DNA
E. the trp repressor will not bind to the trp operator because the repressor cannot dimerize
A. the trp repressor will have tryptophan bound to it
Premature termination of transcription from the trp operon occurs at the end of the leader RNA when

A. when regions 3 and 4 of the leader RNA base pair with each other
B. when regions 2 and 3 of the leader RNA base pair with each other
C. when ribosomes stall at tryptophan codons within region 1 of the leader RNA
D. when the leader peptide interacts with RNA polymerase
A. when regions 3 and 4 of the leader RNA base pair with each other
In E. coli the inability of the lac repressor to bind an inducer would result in

A. no substantial synthesis of B-galactosidase
B. constitutive synthesis of B-galactosidase
C. inducible synthesis of B-galactosidase
D. synthesis of inactive B-galactosidase
E. synthesis of B-galactosidase only in the absence of lactose
A. no substantial synthesis of B-galactosidase
During the synthesis of secretory proteins on the rough ER, the signal recognition particle (SRP) binds to

A. the signal sequence
B. the signal recognition particle receptor
C. the ribosome
D. all of the above
E. none of the above
D. all of the above
Which of the following is NOT characteristic of eukaryotic enhancer elements

A. activity independent of their orientation (sequence can be inverted without effect)
B. activity is dependent on distance from the start site of transcription
C. may be found several kilobases from the promoter
D. may be positioned at the 5' end or the 3' end of the gene
E. increase the level of transcription of genes under their control
B. activity is dependent on distance from the start site of transcription
Which one of the following statements about the regulation of RNA polymerase II transcription in eukaryotes is false

A. cis-acting regulatory sequences can be located over 10,000 base pairs upstream of the transcription start site of the gene they are involved in regulating
B. cis-acting regulatory sequences can be located downstream of the polyadenylation site of the gene they are involved in regulating
C. cis-acting regulatory sequences can be located within an intron of the gene they are involved in regulating
D. the cis-acting sequences involved in activation or repression of transcription are usually recognized directly by RNA polymerase II
E. trans-acting proteins that activate transcription usually have distinct domains (different regions within the protein) that are involved in DNA binding and transcriptional activation
D. the cis-acting sequences involved in activation or repression of transcription are usually recognized directly by RNA polymerase II
When wild-type E. coli are growing on media that contains lactose as the sole energy source (the media contains lactose but no glucose) which of the following is true

A. there is very little or no transcription of the lac operon
B. the lac repressor protein binds strongly to the lac operator
C. the intracellular level of cyclic AMP is low
D. CRP (the cAMP receptor protein) binds strongly to a DNA sequence near the lac promoter
E. transcription of the lac operon terminates prematurely
D. CRP (the cAMP receptor protein) binds strongly to a DNA sequence near the lac promoter
A set of genes from Bacillus subtilis that encode proteins required for sporulation have conserved DNA sequences -35 and -10 nucleotides before the site of transcript initiation, although the sequence at -35 is different from that of most other genes from that species, which of the following best explains this difference

A. a novel sigma factor is required for transcription initiation at these genes
B. the -35 sequence is the binding site for a repressor of transcription
C. the replication of these genes requires a specifically modified DNA polymerase
D. translation of the mRNAs transcribed from these genes requires specific ribosomes that recognize a modified Shine-Dalgarno sequence
E. transcription of these genes is induced by cAMP
A. a novel sigma factor is required for transcription initiation at these genes
A silent mutation in a gene results in

A. no change in the nucleotide sequence of the mRNA encoded by the gene
B. no change in the amino acid sequence of the protein encoded by the gene
C. no expression of the protein encoded by the gene
D. an amino acid substitution that has a significant effect on the functional activity of the protein encoded by the gene
E. a shift of the translational reading frame
B. no change in the amino acid sequence of the protein encoded by the gene
Possesses a single recognition particle

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
B. eukaryotes only
Possesses a signal peptidase

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
B. eukaryotes only
Employs dynein and kinesin for fast axonal transport

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
B. eukaryotes only
Peptide bond formation catalyzed by a RNA molecule

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
C. both prokaryotes and eukaryotes
presence of Shine-Delgarno sequence

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
A. prokaryotes only
AUG is the start codon

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
C. both prokaryotes and eukaryotes
mRNA is translated 3' -> 5'

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
D. neither
N-formyl methionine

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
A. prokaryotes only
GC and CAAT boxes

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
B. eukaryotes only
Has coordinately regulated gene clusters referred to as operons

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
A. prokaryotes only
Terminates translation when a release tRNA binds to a stop codon

A. prokaryotes only
B. eukaryotes only
C. both prokaryotes and eukaryotes
D. neither
B. eukaryotes only
Zinc fingers are important in cellular regulation because they are

A. at the catalytic site of many proteins
B. a structural motif of many DNA-binding proteins
C. characteristic of palindromic stretches of unique-sequence DNA
D. restricted to the cytoplasmic domain of growth factor receptors
E. structures with high redox potential
B. a structural motif of many DNA-binding proteins
In bacterial cell, a mutation in an aminoacyl-tRNA synthetase leads to charging of the entire tRNA ser population with alanine. Which of the following describes the result of using these aminoacyl tRNAs for protein synthesis

A. the alanyl-tRNAser will not function in protein synthesis
B. proteins synthesized will contain neither alanine nor serine
C. proteins synthesized will contain only serine where alanine would normally occur
D. proteins synthesized will contain only alanine where serine would normally occur
E. proteins synthesized will randomly contain either alanine or serine where serine would normally occur
D. proteins synthesized will contain only alanine where serine would normally occur
Observing muscle tissue under the microscope you would find that during contraction

A. the z lines move farther apart
B. the length of thick and thin filaments changes significantly
C. the microtubules disassembled
D. the sarcoplasm switched from gel to sol and back again
E. the H zones and I bands become smaller
E. the H zones and I bands become smaller
The trp operon in E. coli is regulated in such a manner as to allow expression of the genes only when cellular levels of tryptophan are low. When tryptophan levels are adequate, the secondary structure of the mRNA halts translation. This form of regulation is known as

A. attenuation
B. transcript initiation regulation
C. positive regulatory control
D. rho-dependent termination
E. nonsense suppression
A. attenuation
Sigma factors can regulate transcription initiation. Which of the following is not an example of sigma factor regulation?

A. some sigma factors recognize promoters for genes responsible for heat shock responses
B. some sigma factors recognize promoters for genes responsible for nitrogen starvation responses
C. bacteriophage may code for sigma factors specific to phage genes
D. eukaryotic organisms have many more sigma factors than prokaryotes
D. eukaryotic organisms have many more sigma factors than prokaryotes
A transcriptional regulator that decreases transcription of a gene from over 200 bp upstream of the transcript initiation site is a

A. enhancer
B. activator
C. silencer
D. repressor
C. silencer
You are investigating a biochemical pathway and discover that it's operon is subject to end product repression. You deduce that it must be

A. an anabolic pathway
B. a constitutive pathway
C. a catabolic pathway
D. an induced pathway
E. a positively regulated pathway
A. an anabolic pathway
The lac repressor is

A. inactive when lactose is present
B. inactive when glucose is present
C. active when both glucose and lactose are present
D. always active
E. not responsive to either glucose or lactose
A. inactive when lactose is present
Which of the following does not apply to eukaryotic gene regulation

A. gene regulation by attenuation
B. regulation as a result of compartmentaliztaion
C. mRNA degradation (turnover)
D. alternative splicing
E. protein degradation (turnover)
A. gene regulation by attenuation
Small molecules that bind directly to mRNAs and affect transcription or translation are binding to regions of the mRNA known as

A. shine-dalgarno sequences
B. the operator region
C. the promoter region
D. ribozymes
E. riboswitches
F. allosteric sites
E. riboswitches
DNA rearrangement in vertebrates occurs in

A. glycolysis genes
B. cell surface protein genes
C. globin genes
D. antibody (immunoglobulin) genes
E. gene rearrangement doesn't occur
D. antibody (immunoglobulin) genes
The ATP burning protein associated with chromosomal movement in mitosis and meiosis is

A. flagellin
B. myosin
C. dynein
D. kinesin
E. actin
F. none of the above
C. dynein
The ATP burning protein associated with bacterial flagellar propulsion is

A. flagellin
B. myosin
C. dynein
D. kinesin
E. actin
F. none of the above
F. none of the above
The ATP burning protein associated with eukaryotic cilliary and flagellar movement is


A. flagellin
B. myosin
C. dynein
D. kinesin
E. actin
F. none of the above
C. dynein
Polycistronic mRNAs encode

A. more than one product via alternative splicing
B. multiple polypeptides without any further processing
C. a single message
D. exclusively archaeal proteins
E. none of the above
B. multiple polypeptides without any further processing
The ribosome is involved in all of the following EXCEPT

A. peptide bond formation
B. binding of protein factors during elongation
C. binding of aminoacyl-tRNA to mRNA
D. binding of mRNA at an initiation codon
E. aminoacylation of tRNA
E. aminoacylation of tRNA
You are examining an enzyme involved in glycolysis: as such you would expect

A. the protein to be a hormone
B. the protein to be induced by glucose
C. the protein to be constitutively expressed
D. the protein to be expressed only during development
E. the protein to be expressed only during mitosis
C. the protein to be constitutively expressed
Dynein is a motor molecule that is characterized by

A. activation of sliding of flagellar microtubules
B. sliding along actin in the sarcomere
C. motion towards the + end of the microtubule
D. motion along intermediate filaments
E. motion towards the minus end of the microtubule
E. motion towards the minus end of the microtubule
If more than one codon specifies the same amino acid, the code is said to be

A. complementary
B. ambiguous
C. redundant
D. degenerate
E. bound by a suppressor tRNA
D. degenerate
An active regulatory protein "turning off" expression is an example of

A. feedback inhibition
B. positive control
C. negative control
D. constitutive regulation
E. attenuation
C. negative control
The ATP burning protein associated with animal cell cytokinesis is

A. flagellin
B. myosin
C. dynein
D. kinesin
E. actin
F. none of the above
B. myosin
Posttranslational processing may include

A. splicing together exteins after removal of inteins
B. splicing together inteins after removal of exteins
C. splicing together exons after removal of introns
D. splicing together intron after removal of exons
E. none of the above
A. splicing together exteins after removal of inteins
Amino acids are added to tRNA molecules by

A. EF TU and EF TS
B. large ribosomal subunit rRNA, acting as a ribozyme
C. IF2 and GTP
D. 1 of 61 aminoacyl tRNA synthetases
E. 1 of 64 aminoacyl tRNA synthetases
F. 1 of 20 aminoacyl tRNA synthetases
F. 1 of 20 aminoacyl tRNA synthetases
The 61 amino acid specifying codons are read by

A. 61 tRNA molecules each of which has a sequence specific to that anticodon
B. much less than 61 tRNAs (-45) that recognize multiple codons for the same amino acid due to wobble
C. protein release factors
D. protein initiation factor IF2 and GTP
B. much less than 61 tRNAs (-45) that recognize multiple codons for the same amino acid due to wobble
The trp repressor is

A. inactive when tryptophan is present
B. active when tryptophan is present
C. always active
D. active when nonsense mutations interrupt trp operon
E. nonexistent since the trp operon is solely regulated by attenuation
B. active when tryptophan is present
Why can't the sodium and potassium pump work at the same time?
If both pumps were open at the same time then there would be a continuous flow of sodium and potassium in and out of the cell so the charge would be neutral instead of alternating between positive and negative. This would not allow you to make ATP any faster.
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