BIOL 230 Cell and Molecular Final Study Guide

Life depends on: a. single, enormously long DNA molecule that contains many genes. b. the stable storage, maintenance, and inheritance of genetic information. c. Temporarily decondens-ing or condensing particular regions of its chromosomes d. None of the above

b

What is the function of tRNA? a. crucial component of ribosomes b. acts as adaptor molecules in protein synthesis c. acts as a binding site for rRNA d. is essential in the transcription process appearing to be necessary for template strands

b

When cells respond to an extracellular signal, they most often convert the information from one form to another. This process is called? a. signal detection b. signal transduction c. signal amplification d. signal prduction

b

at which site on the DNA of a gene does RNA polymerase release its newly made RNA? a. poly-a tail b. terminator c. TATA box d. stop codon

b

In present-day organisms, which trait or gene is commonly acquired by horizontal gene transfer? a. antibiotic resistance b. lactose tolerance c. sickle cell anemia d. beta globin

a

PI 3 kinase acts by phosphorylating what molecule(s)? a. inositol phospholipids b. serines or threonines on protein kinases that phosphorylate Akt c. serines or thronines of Akt d. tyrosines of Akt

a

What is a retrotransposon? a. mobile genetic element b. breaks down DNA cell wall c. prevents a cell from dividing d. a retrovirus

a

almost half of the human genome consists of what? a. mobile genetic elements b. genes that code for proteins c. introns d. regulatory sequences

a

if DNA is damaged or incompletely replicated in S phase, the inhibition of which of these molecules prevents the cell from entering M phase? a. Cdc25 b. p53 c. Cdc6 d. S-Cdk

a

microtubles capture chromosomes by binding specifically to which of the following? a. kinetochores on the sister chromatids b. telomeres on the condensed chromosomes c. condensins on the condensed chromosomes d. cohesins on the sister chromatids

a

the activation of M-Cdk leads to which of the following? a. exit from mitosis b. onset of G2 phase c. onset of mitosis d. exit from S phase

a

the long noncoding RNNA Xist silences genes on the X chromosome by doing what? a. promoting the formation of heterochromatin b. acting as an antisense transcript that binds to mRNAs c. producing siRNAs d. producing miRNAs

a

the translation of an mRNA begins at the start codon. what is the sequence of this codon? a. AUG b. UGG c. UAG d. AGU

a

to begin transcription, eukaryotic RNA polymerase recognizes nucleotide sequences in what region of the DNA? a. promoter region b. initiator region c. G-C rich region d. terminator region

a

what do both retroviruses and retrotransposons do? a. integrate into the host cell genome b. surround themselves with a protein coat c. use DNA as a template for DNA synthesis d. escape from cells and move to other cells

a

what does depurination refer to? a. the loss of A or G bases from DNA b. the loss of C and T bases from DNA c. depurination is the movement of water through the bloodstream d. a and c

a

what is the best term for an RNA molecule that possesses catalytic activity? a. ribozyme b. ribosomal RNA c. enzyme d. RNase

a

what is the function of rRNA? a. crucial components of ribosomes b. begin replication c. crucial components of chromosomes d. carry instruction for making proteins

a

what is the mitotic spindle made of? a. microtubules b. actin and myosin c. condensins d. cohesins

a

when a cell is acutely injured, it usually dies by which process? a. necrosis b. endocytosis c. apoptosis d. phagocytosis

a

where do transcription regulators usually bind on a DNA double helix? a. major groove b. minor groove c. 5' end d. 3' end

a

which biochemical reaction is catalyzed by a ribosome? a. peptide bond formation in protein synthesis b. peptide bond hydrolysis by proteases c. DNA polymerization during DNA replication d. RNA polymerization during transcription in eukaryotes

a

which of the following is considered a housekeeping protein? a. RNA polymerase b. insulin c. hemoglobin d. cortisol

a

which type of molecule has the potential to perform the catalytic act of reproducing itself? a. RNA b. DNA c. polysaccharides d. proteins

a

t/f the error rate of DNA replication is reduced both by proofreading by DNA and by DNA mismatch repair

True

before a cell divides: a. It must accurately replicate the vast quantity of genetic information carried in its DNA b. DNA polymerase synthesizes new DNA in the 5ʹ-to-3ʹ direction, only the leading strand at the replication fork can be synthesized in a continuous fashion c. homologous recombination can flawlessly repair double strand breaks (and many other types of DNA damage) using an undamaged homologous double helix as a template d. none of the above

b

many of the extracellular molecules that regulate inflammation are released locally at the site of infection. what corm of cell to cell signaling is being used? a. neuronal b. paracrine c. endocrine d. contact-dependent

b

most of the diversity in the rates of cell division in the adult body lies in variations in the time that each cell spends in which phase(s)? a. S phase and M phase b. G1 phase and G0 phase c. S phase d. G1 phase and G2 phase

b

the assembly of general transcription factors at a eukaryotic promoter typically begins at what site? a. TFIID sequence b. TATA box c. the start codon d. the sigma site

b

the cell cycle control system initiates chromosome segregation only after which of the following has occurred? a. DNA has been completely replicated and the chromosomes have decondensed b. the duplicated chromosomes are correctly aligned on the mitotic spindle c. M phase is complete d. the cell stops growing

b

the entire period between one M phase and the subsequent M phase is called what? a. anaphase b. interphase c. G1 phase d. prophsase

b

transcription is catalyzed by: a. nucleosidase b. RNA polymerase c. DNA polymerase d. transcriptase

b

what must happen for a Cdk to be active? a. it must be switched on by proteolysis b. it must bind to its cyclin partner c. it must dissociate from its bound cyclin d. it must increase in concentration at a specific time in the cycle

b

when compared to each other, the two replication forks that form at an origin of replication move in which direction? a. in same direction b. in opposite direction c. at the beginning they move same direction then change to opposite direction d. none of the above

b

which is NOT specifically targeted for destruction by the proteasome? a. damaged proteins b. phosphorylated proteins c. misfolded proteins d. short lived regulatory proteins

b

which is true of the GTP binding proteins that participate in intracellular signaling? a. only trimeric GTP binding proteins participate in intracellular cell signaling b. only trimeric GTP binding proteins relay messages from G protein coupled receptors c. only trimeric GTP binding proteins interact with guanine nucleotide exchange factors (GEFs) d. only monomeric GTP binding proteins relay messages from G protein coupled receptors

b

which of the following does not cause a mutation? a. UV rays b. evolution c. diet d. genetics

b

which of these represents a mechanism used to terminate a signal transmitted by activated RTKs? a. tyrosine kinases remove the phosphates from RTKs and other intracellular signaling proteins b. the RTKs are internalized and digested in lysosomes c. the RTK is inactivated by phospholipase C d. SH2 domains are internalized and digested in lysosomes

b

which statement about cell signaling is correct? a. each type of extracellular signal molecule induces the same response in all target cells b. each receptor is generally activated by only one type of signal molecule c. all extracellular signal molecules act by binding to receptors on the cell surface d. each receptor triggers one particular type of cell behavior, for example, activating gene expression

b

why does nitric oxide (NO) act as a paracrine signal that affects only neighboring cells? a. it diffuses rapidly into the atmosphere b. it is rapidly converted to nitrates and nitrites in the ECF c it is rapidly washed away by the bloodstream d. call surface NO receptors are expressed only on cells in close proximity to NO signaling cells

b

phragmoplast is built by vesicles largely originating from which organelle? a. chloroplast b. vacuole c. golgi apparatus d. endoplasmic reticulum

c

telomerase a. makes a bacterial cell chromosome look circular b. prevents eukaryotic cells from becoming linear c. prevents eukaryotic chromosomes from shortening with each cell division d. all of the above

c

that is true of the GTP binding proteins that act as molecular switches inside cells? a. they turn themselves on by phosphorylating GDP to form GTP b. they turn themselves on by hydrolyzing GTP to form GDP c. they are active when GTP is bound d. they are active only in their trimeric forms

c

the nucleotide sequences of which of the following have been used to create a single all encompassing tree of life? a. immunoglobulin genes b. leptin gene c. rRNA gene d. myosin genes

c

the signal to commence DNA replication comes from which of the following? a. the destruction of Cdc6 b. the desxtruction of M-Cdk c. S-Cdk d. ORD

c

what are homologous genes? a. genes that are present in the same organism b. genes that encode proteins that fold into the same shapes c. genes that are similar in their nucleotide sequence bc of a common ancestry d. genes that encode proteins that perform similar functions

c

what do cells do during the G1 phase? a. replicate and repair DNA b. destroy cyclins and separate sister chromatids c. repair DNA damage and destroy cyclins d. replicate DNA and separate sister chromatids

c

what do the phosphorylated tyrosines on activated RTKs do? a. they serve as binding sites for G proteins b. they activate the enzymatic activity of the RTKs c. they serve as binding sites for a variety of intracellular signaling proteins d. they promote receptor internalization

c

what is an operon? a. a set of genes that is constitutively active b. a short sequence of DNA to which a transcription regulator binds c. a set of genes transcribed as a single mRNA from a single promoter d. a set of genes controlled by the binding of two or more transcription regulators

c

what is the contractile ring made of? a. integrins b. microtubules c. actin and myosin d. condensins

c

what is the function of mRNA? a. begins replication b. crucial components of ribosomes c. carry instruction for making proteins d. crucial components of chromosomes

c

what is the most general term for a change in a single nucleotide pair? a. neutral mutation b. nonsense mutation c. point mutation d. missense mutation

c

what is true of ion channel coupled receptors? a. they are found only in nerve cells b. they are voltage gated c. they transduce signals in a simple and direct manner d. they integrate multiple signals at the same time

c

what type of enzyme removes damaged DNA from the rest of the DNA molecule? a. kinase b. proteinase k c. nuclease d. polymerase

c

which describes some stages of the cell cycle in order? a. cytokinesis, DNA replication, chromosomal segregation b. DNA replication, chromosomal segregation, cytokinesis c. chromosomal segregation, cytokinesis, DNA replication d. none of the above

c

Although all of the steps involved in expressing a gene can in principle be regulated, what is the most important stage of control for most genes? a. mRNA degradation b. mRNA translation c. RNA transport and localization d. transcription initiation

d

Ras is activated by a Ras activating protein that does what? a. dephosphorylates Ras b. phosphorylates Ras c. causes Ras to hydrolyze its bound GTP d. causes Ras to exchange GDP for GTP

d

What is the central dogma of molecular biology? a. much like all viruses, all cells use DNA to encode genetic info b. for a given individual, the genetic info contained in the DNA of every cell is identical c. the earliest cells on earth most likely used RNA to store and copy genetic info d. within the cell, genetic info flows from DNA to RNA to protein

d

What structure in an interphase eukaryotic cell is the site of ribosomal RNA transCription? a. Ribosomes b. Lysosomes c. Golgi Complex d. Nucleolus

d

T/F After acetylcholine is secreted from cells, it is long lived because it has to reach target cells all over the body

false acetylcholine is short lived and exerts its effects locally. indeed the consequences of prolonging its lifetime can be disastrous. compounds that inhibit the enzyme acetylcholinesterase which normally breaks down acetylcholine at a nerve-muscle synapse, are extremely toxic; for example the nerve gas sarin used in chemical warfare is an acetylcholinesterase inhibitor

t/f calmodulin regulates the intracellular Ca2+ concentration

false calmodulin senses but does not regulate Ca2+

true or false: a bacterial replication fork is asymmetrical because it contains two DNA polymerase molecules tat are structurally distinct

false identical DNA polymerase molecules catalyze DNA synthesis on the leading and lagging strand of a bacterial replication fork. the replication fork is asymmetrical bc the lagging strand is made in pieces whil the leading strand is synthesized continuously.

t/f: okazaki fragments are removed by a nuclease that degrades RNA

false: Okazaki fragments initially contain both RNA primers and DNA but only the RNA primers are removed by RNA nucleases

Heterochromatin

highly condensed region of an interphas chromosome; generally gene-poor and transcriptionally inactive

the bonds that form bt the anticodon of a tRNA molecule and the three nucleotides of a codon in mRNA are ___________.

hydrogen bonds that form when the tRNA is at the A site

nucleosome

includes the DNA wrapped around the histone core plus a segment of linker DNA

each eukaryotic chromosome must contain the following DNA sequence elements:

multiple origins of replication, two telomeres, and one centromere

interphase chromosomes

nuclear divisions- that is, in interphase- the chromatin of the interphase chromosomes is in a relatively extended form in the nucleus

mitotic chromosome

replicated chromosomes become condensed into mitotic chromosomes which are transcriptionally inactive and are designed to be readily distributed bt the two daughter cells

what is the order in which the following events occur during cell division? and where does cytokinesis fit in? a. anaphase b. metaphase c. prometaphase d. telophase e. mitosis f. prophase

the order is F C B A D (prophase, prometaphase, metaphase, anaphase, anaphase) Together these five steps are referred to as mitosis. Cytokinesis is the last step in M phase, which overlaps with anaphase and telophase. Mitosis and cytokinesis are both part of M phase.

t/f IP3 is produced directly by cleavage of an inositol phospholipid without incorporation of an additional phosphate group/.

true

t/f both the GTP bound alpha subunits and nucleotide free beta y complexes- but not GDP bound, fully assembled G proteins- can activate other molecules downstream of GPCRs

true

t/f cancer can result from the accumulation of mutations in somatic cells

true

t/f in the absence of DNA repair, genes become less stable

true

t/f non of the aberrant bases formed by deamination occur naturally in DNA

true

t/f the extracellular signal molecule acetylcholine has different effects on different cell types in an animal and often binds to different cell surface receptor molecules on different cell types.

true

t/f different signals originating from the plasma membrane can be integrated by cross-talk bt different signaling pathways inside the cell

true

t/f tyrosine phosphorylation serves to build binding sites for other proteins to bind to RTKs

true

How does PI 3-kinase activate the Akt kinase after activation of RTK?

when PI 3-kinase is activated by an activated RTK, it phosphorylates a specific inositol phospholipid in the plasma membrane. The resulting phosphorylated inositol phospholipid then recruits to the plasma membrane both Akt and another protein kinase that helps phosphorylate and activate Akt. A third kinase that is permanently associated with the membrane also helps activate Akt.

The nucleotide sequence of one DNA strand of a DNA double helix is 5ʹ-GGATTTTTGTCCACAATCA-3ʹ.What is the sequence of the complementary strand?

5ʹ-TGATTGTGGACAAAAATCC-3

How many possible nucleotide sequences are there for a stretch of single-stranded DNA that is N nucleotides long?

A single-stranded DNA molecule that is N nucleotides long can have any one of 4N possible sequences

which of the following statements are correct? explain your answers a. an individual ribosome can make only one type of protein b. all mRNAs fold into particular 3-d structures that are required for translation c. the large and small subunits of an individual ribosome always stay together and never exchange partners d. ribosomes are cytoplasmic organelles that are encapsulated by a single membrane e. because the two strands of DNA are complementary, the mRNA of a given gene can be synthesized using either strand as a template f. an mRNA may contain the sequence ATTGACCCCGGTCAA g. the amount of a protein present in a cell depends on its rate of synthesis, its catalytic activity, and its rate of degradation

ALL ARE FALSE!!! a. ribosomes can make any protein that is specified by the particular mRNA that they are translating. after translation, ribosomes are released from the mRNA and can then start translating a different mRNA. it is true, however, that a ribosome can only make one type of protein at a time b. mRNAs are translated as linear polymers; there is no requirement that they have any particular folded structure. in fact, such structures that are formed by mRNA can inhibit translation, because the ribosome has to unfold the mRNA in order to read the message it contains c. ribosomal subunits can exchange partners after each round of translation. after a ribosome is released from an mRNA, its two subunits dissociate and enter a pool of free small and large subunits from which new ribosomes assemble around a new mRNA d. ribosomes are not individually enclosed in a membrane e. the position of the promoter determines the direction in which transcription proceeds and therefore which of the two DNA strands is used as the template. transcription of the other strand would produce an mRNA with a completely different (and in most cases meaningless) sequence f. RNA contains uracil but not thymine g. the level of a protein depends on its rate of synthesis and degradation but not on its catalytic activity

which of the following statements are correct? explain your answers a. in bacteria but not in eukaryotes, many mRNAs contain the coding region for more than one gene b. most DNA binding proteins bind to the major groove of the DNA double helix c. of the major control points in gene expression (transcription, RNA processing, RNA transport, translation, and control of a protein's activity), transcription initiation is one of the most common

ALL ARE TRUE!!! a. prokaryotic mRNAs are often transcripts of entire operons. ribosomes can initiate translation at the internal AUG start sites of these "polycistronic" mRNAs b. the major groove of double stranded DNA is sufficiently wide to allow a protein surface, such as one face of an alpha helix, access to the base pairs. the sequence of H bond donors and acceptors in the major groove can then be "read" by the protein to determine the sequence of the DNA c. it is advantageous to exert control at the earliest possible point in a pathway. this conserves metabolic energy because unnecessary products are not made

the flow of genetic information in all living cells is: a. RNA-DNA-PROTEIN b. DNA-RNA c. PROTEIN-RNA-DNA d. DNA-RNA-PROTEIN

D

In the DNA of certain bacterial cells, 13% of the nucleotides contain adenine. What are the percentages of the other nucleotides?

Thymine=13% Adenine=13% Guanine=37% Cytosine=37%

which of the following statements are correct? explain your answers. a. cells do not pass from G1 to M phase of the cell cycle unless there are sufficient nutrients to complete and entire cell cycle b. apoptosis is mediated by special intracellular proteases, one of which cleaves under nuclear lamins c. developing neurons compete for limited amounts of survival factors d. some vertebrate cell cycle control proteins function when expressed in yeast cells e. the enzymatic activity of a Cdk protein is determined both by the presence of a bound cyclin and by the phosphorylation state of the Cdk

a. false: there is no G1 to M phase transition. The statement is correct, however, for the G1 to S phase transition, in which cells commit themselves to a division cycle. b. true c. true d. true e. true

which of the following statements are correct? explain your answers. a. centrosomes are replicated before the M phase begins b. two sister chromatids arise by replication of the DNA of the same chromosome and remain paired as they line up on the metaphase plate c. interpolar microtubules attach end to end and are therefor continuous from one spindle pole to the other d. microtubule polymerization and depolymerization and microtubule motor proteins are all required for DNA replication e. microtubules nucleate at the centromere and then connect to the kinetochores which are structures at the centrosome regions of chromsomes

a. true b. true c. false: the ends of interpolar microtubles overlap and attach to one another via proteins (including motor proteins) that bridge between the microtubles d. false: microtubles and their motor proteins play no role in DNA replication e. false: to be a correct statement, the terms "centromere" and "centrosome" must be switched.

what do you suppose happens in mutant cells that: a. cannot degrade M cyclin? b. always express high levels of p21? c. cannot phosphorylate Rb?

a. would enter mitosis but would not be able to exit mitosis b. would arrest permanently in G1 because the cyclin-Cdk complexes that act in G1 would be inactivated c. would not be able to activate the transcription of genes required for cell division because the required transcription regulators would be constantly inhibited by unphosphorylated Rb.

what are the similarities and differences bt the reactions that lead to the activation of G proteins and the reactions that lead to the activation of Ras?

activation in both cases depends on proteins that catalyze GDP-GTP exchange on the G protein or Ras protein. Whereas activated GCPRs perform this function directly for G proteins, enzyme linked receptors assemble multiple signaling proteins into a signaling complex when the receptors are activated by phosphorylation; one of these proteins is an adaptor protein that recruits a guanine nucleotide exchange factor that fulfills this function for Ras.

nucleotides in each strand of DNA are held together by what type of bond? a. hydrogen bonds b. covalent bonds c. phosphodiester bonds d. nucleic bonds

c

compare and contrast signaling by neuron, which secrete neurotransmitters at synapses, with signaling carried out by endocrine cells, which secrete hormones into the blood; discuss the relative advantages of the two mechanisms.

both types of signaling can occur over a long range: neurons can send action potentials along very long axons (think of the axons in the neck of a giraffe, for example) and hormones are carried via the bloodstream throughout the organism. because neurons secrete large amounts of neurotransmitters at a synapse, a small, well-defined space between two cells, the concentrations of these signal molecules are high; neurotransmitter receptors, therefore, need to bind to neurotransmitters with only low affinity. Hormones, in contrast, are vastly diluted i the bloodstream where they circulate at often minuscule concentrations; hormone receptors therefore generally bind with their hormone with extremely high affinity. wheras neuronal signaling is a private affair, with one neuron talking to a select group of target cells through specific synaptic connections, endocrine signaling is a public announcement, with any target cell with appropriate receptors able to respond to the hormone in the blood. neuronal signaling is very fast, limited only by the speed of propagation of the action potential and the workings of the synapse, whereas endocrine signaling is slower, limited by blood flow and diffusion over larger distances.

56) The transcription initiation site of a eukaryotic gene is found at which location? a. where RNA polymerase first binds b. where general transcription factors bind c. where RNA synthesis begins d. where transcription regulators bind

c

Proteasomes act primarily on proteins that have been marked for destruction by the attachment of which small protein? a. termination factor b. histone c. ubiquitin d. prion

c

What is the general name given to the most highly condensed form of chromatin? a. chromatid b. chromatin c. heterochromatin d. centromere

c

Which form of control directly influences which mRNAs are selected by ribosomes for the synthesis of proteins? a. mRNA degradation control b. transcriptional control c. translational control d. mRNA processing and localization control

c

Which of the following represents the specialized DNA sequence that attaches to microtubules and allow duplicated eukaryotic chromosomes to be separated during M phase? a. centrosomes b. cytosines c. centromere d. chromatin

c

in addition to its role in DNA repair, homologous recombination is also responsible for generating genetic diversity during what process? a. mitosis b. interphase c. meiosis d. cytokinesis

c

in eukaryotes, what separate component generally encodes individual protein domans? a. codons b. genes c. exons d. introns

c

most of the genetic variation in the human genome takes what form? a. DNA duplications or deletions b. copy-number variations c. signal amplification d. the size of short tandem repeats

c

mutation is: a. death of G2 phase cells b. temporal change in DNA in a DNA sequence c. permanent change in a DNA sequence d. treatable viral disease

c

chromatin

complex of DNA and proteins that makes up the chromosomes in a eukaryotic cell

for a retrotransposon, reverse transcriptase produces DNA copies using which of the following as a template? a. transposase b. a single strand viral genome c. the host cell's RNA polymerase d. RNA

d

how or where do most transcription regulators bind? a. to the major groove of RNA b. to the minor groove of DNA c. to a DNA sequence called the homeodomain d. as dimers

d

many mobile genetic elements encode an enzyme that mediates their movement. what is this enzyme called? a. exonuclease b. transposon c. flippase d. transposase

d

signaling via a GPCR ceases when which condition occurs? a. the G protein dissociated from the activated GPCR b. the G protein associates with an activated GPCR c. the alpha subunit exchanges GDP for GTP d. the alpha subunit hydrolyzes its bound GTP

d

the conversion of the genetic instructions in replication, transcription, and translation is termed: a. genome b. chromosomal region c. gene expression d. epigenetics

d

the mitotic spindle begins to assemble in which phase of the cell cycle? a. prometaphase b. anaphase c. metaphase d. prophase

d

what are small intracellular signaling molecules often called? a. transmitter gated ion channels b. extracellular signaling molecules c. intracellular signaling proteins d. second messengers

d

which of the following cell types when fully differentiated does not divide to form new cells? a. fibroblasts b. liver cells c. smooth muscle cells d. skeletal muscle cells

d

which of the following occurs during metaphase? a. nuclear envelope breakdown b. chromosomes being captured by spindle microtubules c. chromosomes being condensed d. chromosomes being aligned under tension at the spindle equator

d

which response to GPCR stimulation would be most rapid? a. change in activation of a set of target genes b. activation of a G protein that activates adenylyl cyclase c. activation of a G protein that activated phospholipase C d. activation of a G protein that regulates the opening of an ion channel

d

which statement about positive feedback regulation is accurate? a. positive feedback is rare in biological systems b. in positive feedback, a molecular switch enhances the response to a signal by activating a component that lies downstream in the pathway c. positive feedback can generate responses that oscillate on and off as the activities or concentrations of the participating components rise and fall d. positive feedback regulation can generate an abrupt, all or none response in which the cell moves from ignoring a signal to responding to it very strongly

d

which would be the best method for determining which genes are being transcribed in a particular cell type? a. electron microscopy b. NMR spectroscopy c. xray crystallography d. RNA sequencing (RNA seq)

d

why does the activation of M-Cdk begin abruptly? a. M cyclin is rapidly phosphorylated and thereby activated b. the mitotic Cdk increases abruptly c. M cyclin increases abruptly d. each M-Cdk complex can activate more M-Cdk

d

histones

one small group of abundant, highly conserved proteins around which DNA wraps to form nucleosomes, structures that represent the most fundamental level of chromatin packing