BIOL-1703 Exam #4

Which of the following statements about the experiment diagrammed in Figure Q19-38 is true?

if you crossed all the round-seeded pea plats from the F2 generation with true-breeding wrinkle-seeded pea plants, you would get more round-seeded pea plants in the next generation than if you crossed all the round-seeded pea plants from the F1 generations with true-breeding wrinkle-seeded pea plants

Which of the following statements about membrane-enclosed organelles is true?

in a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane

Which of the following statements is true? (Anaphase)

in anaphase B, microtubules associated with the cell cortex shorten

Where are proteins in the chloroplast synthesized?

in both the cytosol and the chloroplast

Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in Figure Q16-58. Figure Q16-58 Which of the following statements is false?

in the absence of a survival signal, Bad is phosphorylated

Figure Q15-31 shows the organization of a protein that resides on the ER membrane. The N- and C-termini of the protein are labeled. Boxes 1, 2, and 3 represent membrane- spanning sequences. Non-membrane-spanning regions of the protein are labeled "X," "Y,"and "Z." Figure Q15-31 Once this protein is fully translocated, where will region Y be?

in the cytoplasm

In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins?

in the cytosol

You have isolated a strain of mutant yeast cells that divides normally at 30C but cannot enter M phase at 37C. You have isolated its mitotic cyclin and mitotic Cdk and find that both proteins are produced and can form a normal M-Cdk complex at both temperatures. Which of the following temperature-sensitive mutations could not be responsible for the behavior of this strain of yeast?

inactivation of an enzyme that ubiquitylates M cyclin

The Retinoblastima (Rb) protein blocks cells from entering the cell cycle by _____.

inhibiting cyclin transcription

Before mitosis, the number of centrosomes must [increase/decrease]. At the beginning of [anaphase/prophase] in animal cells, the centrosomes separate in a process driven partly by interactions between the [plus/minus] ends of microtubules arising from the two centrosomes. Centrosome separation initiates the assembly of the bipolar mitotic spindle and its associated with a sudden [increase/decrease] in the dynamic instability of microtubules. In comparison with an interphase microtubule array, a mitotic aster contains a [smaller/larger] number of [longer/shorter] microtubules. Extracts from M-phase cells exhibit [increased/decreased/unchanged] rates of microtubule polymerization and increased frequencies of microtubule [shrinkage/growth]. The changes in microtubule dynamics are largely due to [enhanced/reduced] activity of microtubule-associated proteins and [increased/decreased] activity of catastrophins. The new balance between polymerization and depolymerization of microtubules is necessary for the mitotic spindle to move the [replicated chromosomes/daughter chromosomes] to the metaphase plate.

inrease prophase plus increase larger shorter unchanged shrinkage reduced increased replicated chromosomes

How does S-Cdk help guarantee that replication occurs only once during each cell cycle?

it phosphorylates the Cdc6 protein, marking it for destruction

Which of the following statements is true? (proteins in the ER)

proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation

Which of the following statements about the protein quality control system in the ER is false?

proteins that are misfolded are degraded in the ER lumen

Which of the following statements about the endoplasmic reticulum is false?

proteins to be delivered to the ER lumen are synthesized on the smooth ER

An extracellular signal molecule can act to change a cell's behavior by acting through cell-surface __________________ that control intracellular signaling proteins. These intracellular signaling proteins ultimately change the activity of __________________ proteins that bring about cell responses. Intracellular signaling proteins can __________________ the signal received to evoke a strong response from just a few extracellular signal molecules. A cell that receives more than one extracellular signal at the same time can __________________ this information using intracellular signaling proteins. __________________ proteins can act as molecular switches, letting a cell know that a signal has been received. Enzymes that phosphorylate proteins, termed ___________, can also serve as molecular switches; the actions of these enzymes are countered by the activity of __________________.

receptors effector amplify integrate GTP-binding protein kinases protein phosphates

Vesicles from the ER enter the Golgi at the ________.

cis Golgi network

Match the class of cell-surface receptor with the best description of its function. Not all descriptors will be used. G-protein-coupled receptors ______ ion-channel-coupled receptors ______ enzyme-coupled receptors ______ A. alter the membrane potential directly by changing the permeability of the plasma membrane B. signal by opening and closing in a ligand-independent manner C. must be coupled with intracellular monomeric GTP-binding proteins D. all receptors of this class are polypeptides with seven transmembrane domains E. discovered for their role in responding to growth factors in animal cells

- all receptors of this class are polypeptides with seven transmembrane domains - alter the membrane potential directly by changing the permeability of the plasma membrane - discovered for their role in responding to growth factors in animal cells

Match the components involved with ER transport with the appropriate cellular location. 1. signal-recognition particle 2. protein translocator 3. mRNA 4. SRP receptor 5. active site of signal peptidase

1. cytosol 2. ER membrane 3. cytosol 4. ER membrane 5. ER lumen

You examine a worm that has two genders: males that produce sperm and hermaphrodites that produce both sperm and eggs. The diploid adult has four homologous pairs of chromosomes that undergo very little recombination. Given a choice, the hermaphrodites prefer to mate with males, but just to annoy the worm, you pluck a hermaphrodite out of the wild and fertilize its eggs with its own sperm. Assuming that all the resulting offspring are viable, what fraction do you expect to be genetically identical to the parent worm? Assume that each chromosome in the original hermaphrodite is genetically distinct from its homolog.

1/16

A diploid cell containing 32 chromosomes will make a haploid cell containing ____ chromosomes.

16

Rank the following cytoskeletal filaments from smallest to largest in diameter _______ intermediate filaments _______ microtubules _______ actin filament _______ myofibril

2 3 1 4

Rank the following types of cell signaling from 1 to 4, with 1 representing the type of signaling in which the signal molecule travels the least distance and the 4 the type of signaling in which the signal molecule travels the largest distance. ____ paracrine signaling ____ contact-dependent signaling ____ neuronal signaling ____ endocrine signaling

3 1 2 4

In the absence of recombination, how many genetically different types of gamete can an organism with five homologous chromosome pairs produce?

32

Meiosis is a highly specialized cell division in which several events occur in a precisely defined order. Please order the meiotic events listed below. 1. loss of cohesins near centromeres 2. chromatid pairing 3. chromosome condensation 4. chromosome replication 5. degradation of cohesins bound to chromosome arms 6. formation of chiasmata (chiasmata = plural of chiasma) 7. homolog pairing 8. alignment of chromosomes at the metaphase plate

4 2 7 6 3 8 5 1

If you crossed the round-seeded plants obtained in the F1 generation with a true-breeding strain of wrinkle-seeded plants, how many round-seeded plants would you expect to obtain in the next generation?

50%

Match each of the main classes of spindle microtubules from list 1 with their functions and features from list 2. A. Interpolar microtubules B. Aster microtubules C. Kinetochore microtubules 1. Stabilized by interactions with each other via motor proteins 2. Interact with the cell cortex 3. Link chromosomes to a spindle pole 4. Depolymerize to promote anaphase A 5. Depolymerize to promote anaphase B

A - 1 B - 2, 5 C - 3, 4

Consider an animal cell that has eight chromosomes (four pairs of homologous chromosomes) in G1 phase. How many of each of the following structures will the cell have at mitotic prophase? A. sister chromatids B. centromeres C. kinetochores D. centrosomes E. centrioles

A - 16 B - 16 C - 16 D - 2 E - 4

Name the stage of M phase in which the following events occur. Place the numbers 1-8 next to the letter headings to indicate the normal order of events. A. alignment of the chromosomes at the spindle equator B. attachment of spindle microtubules to chromosomes C. breakdown of nuclear envelope D. pinching of cell in two E. separation of two centrosomes and initiation of mitotic spindle assembly F. re-formation of the nuclear envelope G. condensation of the chromosomes H. separation of sister chromatids

A. 5, metaphase B. 4, prometaphase C. 3, prometaphase D. 8, cytokinesis E. 2, prophase F. 7, telophase G. 1, prophase H. 6, anaphase

Cells can pause in G1 when DNA is damaged, and can pause in S when there are replication errors. Which of the mechanism below applies to this cell cycle arrest. (a) p53 activates the transcription of a Cdk inhibitor. (b) Cyclins are Ubiquitinated and destroyed. (c) Cdk is able to phosphorylate its substrates. (d) The Cdc25 phosphatase is inhibited.

A. G1 arrest B. neither C. both D. S-phase arrest

Cystic fibrosis results from mutations in a single gene that lies on Chromosome 7. Only homozygous mutant (ff) individuals are sick; homozygous wild-type (FF) and heterozygous (Ff) individuals are healthy.A healthy married couple has one child with cystic fibrosis and the wife is pregnant with a second child. A. What is the genotype of the mother? the father? B. What is the chance that the second child will have cystic fibrosis?

A. Ff and Ff B. 1/4 or 25% chance

Indicate which of the three major classes of cytoskeletal elements each statement below refers to. A. monomer that binds to ATP B. includes keratin and neurofilaments C. important for formation of the contractile ring during cytokinesis D. supports and strengthens the nuclear envelope E. their stability involves a GTP cap F. used in the eukaryotic flagellum G. a component of the mitotic spindle H. can be connected through desmosomes I. directly involved in muscle contraction J. abundant in filopodia

A. actin B. intermediate filaments C. actin D. intermediate filaments E. microtubules F. microtubules G. microtubules H. intermediate filaments I. actin J. actin

Name the membrane-enclosed compartments in a eukaryotic cell where each of the functions listed below takes place. A. photosynthesis B. transcription C. oxidative phosphorylation D. modification of secreted proteins E. steroid hormone synthesis F. degradation of worn-out organelles G. new membrane synthesis H. breakdown of lipids and toxic molecules

A. chloroplast B. nucleus C. mitochondria D. Golgi apparatus and rough endoplasmic reticulum E. smooth ER F. lysosome G. ER H. peroxisome

Indicate whether each of the following is true for meiosis, mitosis, both, or neither. A. formation of a bivalent B. genetically identical products C. condensation of chromosomes D. segregation of all paternal chromosomes to one cell E. involvement of DNA replication

A. meiosis B. mitosis C. both D. neither E. both

Match the target of the G protein with the appropriate signaling outcome. adenylyl cyclase ________ ion channels _________ phospholipase C _________ A. cleavage of inositol phospholipids B. increase in cAMP levels C. changes in membrane potential

B C A

Irradiated mammalian cells usually stop dividing and arrest at a G1 checkpoint. Place the following events in the order in which they occur. A. production of p21 B. DNA damage C. inhibition of cyclin-Cdk complexes D. accumulation and activation of p53

B D A C

Microtubules are formed from the tubule heterodimer, which is composed of nucleotide-binding ______ protein and the _____ protein. Tubulin dimers are stacked together into protofilaments; _____ parallel protofilaments form the tubelike structure of a microtubule. _____ rings are important for microtubule nucleation and are found in the ______, which is usually found near the cell's nucleus in cells that are not undergoing mitosis A microtubules that is quickly growing will have a _____ cap that helps prevent the loss of subunits from its growing end. Stable microtubules are used in cilia and flagella; these microtubules are nucleated from a _____ and involve a "_____ plus two" array of microtubules. The motor protein ______ generates the bending motion in cilia; the lack of this protein can cause Kartagener's syndrome in humans.

B-tubulin a-tubulin thirteen y-tubulin centrosome GTP basal body nine dynein

Place the following in order of size, from the smallest to the largest. A. protofilament B. microtubule C. alpha-tubulin D. tubulin dimer E. mitotic spindle

C D A B E

Figure Q16-61 shows that intracellular signaling pathways can be highly interconnected. From the information in Figure Q16-61, which of the following statements is incorrect?

CaM-kinase is only activated when the GPCR is active and not when the RTK is active

Which of the following statements about vesicle budding from the Golgi is false?

Clathrin molecules are important for binding to and selecting cargoes for transport

The following proteins are important for cell movement. Match the following proteins with their function. myosin filament ______ ARP Proteins _______ profilin ______ integrins ______ formins ________ A. nucleation of new actin filaments at the side of an existing filament B. regulation of the availability of actin monomers C. important for the growth of straight, unbranched actin filaments D. contracting the rear of the cell E> involvement in focal contacts

D A B E C

Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels?

ER -> Golgi -> plasma membrane

You engineer yeast cells that express the M cyclin during S phase by replacing the promoter sequence of the M cyclin gene with that of S cyclin. Keeping in mind that yeast cells have one common Cdk that binds to all cyclins, which of the following outcomes is least likely during this experiment?

G1 cyclins will be expressed during S phase

Which organelle fragments during mitosis?

Golgi apparatus

The cell cycle consists of an alternation between ________, which appears as a period of dramatic activity under the microscope, and a preparative period called ___________, which consists of three phases called ________, _________, and __________. During M phase, the nucleus divides in a process called __________, and the cytoplasm splits in two in a process called _________. The cell-cycle control system relies on sharp increases in the activities of regulatory proteins called ___________, or ___________, to trigger S phase and M phase. Inactivation of _________ is required to exit from M phase after chromosome segregation.

M phase interphase G1 phase S phase G2 phase mitosis cytokinesis cyclin-dependent kinases Cdks M-Cdk

You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells. The hypothesis that best explains this localization is ________________.

MtA binds to GTP-bound tubulin on microtubules

Cells signal to one another in various ways. Some use extracellular signal molecules that are dissolved gases, such as __________________, which can diffuse easily into cells. Others use cytokines, which bind to cytokine receptors. Cytokine receptors have no intrinsic enzyme activity but are associated with cytoplasmic tyrosine kinases called __________________s, which become activated on the binding of cytokine to its receptor and go on to phosphorylate and activate cytoplasmic transcriptional regulators called __________________s. Some intracellular signaling pathways involve chains of protein kinases that phosphorylate each other, as seen in the __________________ signaling module. Lipids can also relay signals in the cell, as we observe when phospholipase C cleaves the sugar-phosphate head off a lipid molecule to generate the two small messenger molecules ______________ (which remains embedded in the plasma membrane) and _____________ (which diffuses into the cytosol).

NO JAK STAT MAP kinase diacylglycerol IP3

Which of the following statements is true? (Kinases)

PI 3-kinase phosphorylates a lipid in the plasma membrane

The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000-dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be true?

QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed

The four phases of the cell cycle, in order, are G1, _________, _________, and ____________. A cell contains the most DNA after ________ phase of the cell cycle. A cell is smallest in size after _________ phase of the cell cycle. Growth occurs in ______, _______, and ________ phases of the cell cycle. A cell does not enter mitosis until it has completed ________ synthesis.

S G2 M S M G1 S G2 DNA

The following happens when a G-protein-coupled receptor activates a G protein.

The alpha subunit exchanges its bound GDP for GTP

Which of the following statements is true? (nuclear membrane)

The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA

Is the following statement true or false? After the nuclear envelope breaks down, microtubules gain access to the chromosomes and, every so often, a randomly probing microtubule captures a chromosome and ultimately connects to the kinetochore to become a kinetochore microtubule of the spindle.

True

Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen by a casacade protein phosphorylation starting from the activation of PKA (Figure 16-23, page 550). Which of the following statements below is false?

a constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available

Finding co-inheritance of a SNP variant and a disease tells scientists that ____________________.

a gene important for causing the disease is linked to the SNP

The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation?

a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization?

a mutation that prevents RGFR from binding to RGF

Male cockroaches with mutations that strongly decrease the function of an RTK called RTKX are oblivious to the charms of their female comrades. This particular RTK binds to a small molecule secreted by sexually mature females. Most males carrying loss-of-function mutations in the gene for Ras protein are also unable to respond to females. You have just read a paper in which the authors describe how they have screened cockroaches that are mutant in RTKX for additional mutations that partly restore the ability of males to respond to females. These mutations decrease the function of a protein that the authors call Z. Which of the following types of protein could Z be?

a protein that stimulates hydrolysis of GTP by the Ras protein

Which of the following would not lead to aneuploidy during meiosis?

a reciprocal rearrangement of parts between non homologous chromosomes (for example, the left arm of chromosome 2 exchanging places with the right arm of chromosome 3)

During fertilization in humans, ____________.

a wave of Ca2+ ions is released in the fertilized egg's cytoplasm

Which of the following protein families are not involved in directing transport vesicles to the target membrane?

adaptins

Which of the following statements about the cytoskeleton is true?

actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end

Which of the following statements is false? (actin filaments)

actin filaments are usually excluded from the cell cortex

Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments?

actin filaments would grow longer

Which of the following statements about the unfolded protein response (UPR) is false?

activation of the UPR occurs when receptors in the cytoplasm sense misfolded proteins

Molecules to be packaged into vesicles for transport are selected by ________.

adaptins

Which of the following conditions is likely to decrease the likelihood of skeletal muscle contraction?

addition of a drug that blocks Ca2+ binding to troponin

Figure Q16-63 shows how normal signaling works with a Ras protein acting downstream of an RTK. You examine a cell line with a constitutively active Ras protein that is always signaling. Which of the following conditions will turn off signaling in this cell line?

addition of a drug that blocks protein Y from interacting with its target

You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activated adenyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cell, while cells that express a mutant, constitutively active version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells?

addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive

Which of the situations below will enhance microtubule shrinkage?

addition of a drug that inhibits GTP exchange on free tubulin dimers

Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K+ channel in the plasma membrane, as shown in Figure Q16-32. Which of the following would enhance this effect of the acetylcholine?

addition of a high concentration of a nonhydrolyzable analog of GTP

You are interested in understanding the regulation of nuclear lamina assembly. To create an in vitro system for studying this process you start with partly purified nuclear lamina subunits to which you will add back purified cellular components to drive nuclear lamina assembly. Before you start doing experiments, your instructor suggests that you consider what type of conditions would be most amenable to the assembly of the nuclear lamina from its individual subunits in vitro. Which of the following conditions do you predict would be most likely to enhance the assembly of the nuclear lamina?

addition of protein kinase inhibitors

Consider the in vitro motility assay using purified kinesin and purified polymerized microtubules shown in Figure Q17-63. The three panels are images taken at 1-second intervals. In this figure, three microtubules have been numbered to make it easy to identify them. Which of the following statements about this assay is false?

addition of the non hydrolyzable ATP analog (AMP-PNP) would cause the microtubules to move faster

Which of the following statements about transport into mitochondria and chloroplasts is false?

after a protein moves through the protein translator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translator in the inner membrane

The formation of a bivalent during meiosis ensures that _______.

all four sister chromatids remain together until the cell is ready to divide

After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode?

all of the above (soluble secreted proteins, ER membrane proteins, plasma membrane proteins)

Which of the following could be considered a true-breeding strain for the seed-shape phenotype?

all of the wrinkle-seeded plants produced in the F2 generation

Which of the following reasons was essential for Mendel's law of independent assortment?

all the traits that Mendel examined involved genes that did not display linkage

Which of the following statements about Medel's experiments is false?

all traits that model studied were recessive

The hydrolysis of GTP to GDP carried out by tubulin molecules ______.

allows the behavior of microtubules called dynamic instability

Which of the following statements about the structure of microtubules is false?

alpha-tubulin and beta-tubulin are covalently bonded to make the tubulin dimer that then assembles into protofilaments

When introduced into mitotic cells, which of the following is expected to impair anaphase B but not anaphase A?

an antibody against the motor proteins that move from the minus end of microtubules toward the plus end

In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated?

and the end of G2

Which of the following statements is true? (Sex)

another name for the fertilized egg is the zygote

Which of the following statements about apoptosis is true?

apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria

Loss-of-function mutations _________.

are usually recessive

Condensins __________.

assemble into complexes on the DNA when phosphorylated by M-Cdk

Which of the following precede the reformation of the nuclear envelope during M phase in animal cells?

assembly of the contractile ring

Most proteins destined to enter the endoplasmic reticulum _______.

begin to cross the membrane while still being synthesized

Figure Q17-40A shows how the movement of dynein causes the flagellum to bend. If instead of the normal situation, the polarity of the adjacent doublet of microtubules were to be reversed (see Figure Q17-40B), what do you predict would happen?

bending would occur, except that the right microtubule doublet would move down relative to the left one

Programmed cell death occurs ___________.

by means of an intracellular suicide program

the single nucleotide polymorphism found in the human population ________.

can be linked into haplotype blocks

Figure Q17-52 shows the leading edge of a lamellipodium. Which of the following statements is false?

capping proteins bind to the minus end of actin filaments

Apoptosis differs from necrosis in that necrosis _________.

causes cells to swell and burst, whereas apoptotic cells shrink and condense

After the first meiotic cell division ________________________.

cells are produced that contain same number of chromosomes as somatic cells

You are examining a cell line in which activation of the Rho family member Rac promotes lamellipodia formation. Which of the following statements is most likely to be true?

cells carrying a Rat mutation that makes Rac act as if it is always bound to GTP will polymerize more branched actin filaments than normal cells

You create cells with a version of Cdc6 that cannot be phosphorylated and thus cannot be degraded. Which of the following statements describes the likely consequence of this change in Cdc6?

cells will be unable to complete DNA synthesis

The principle microtubule-organizing center in animal cells is the _______.

centrosome

Circle the phrase in each pair that is likely to occur more rapidly in response to an extracellular signal. A. changes in cell secretion / increased cell division B. changes in protein phosphorylation / changes in proteins being synthesized C. changes in mRNA levels / changes in membrane potential

changes in cell secretion changes in protein phosphorylation changes in membrane potential

Which of the following statements is true? (chaperone proteins)

chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes

During recombination _______.

chiasmata hold chromosomes together

Sickle-cell anemia is caused by a mutant allele of a hemoglobin gene. Individuals with two mutant alleles have sickle-cell anemia. individuals homozygous and heterozygous for the mutant gene are more resistant to malaria than those with two wild-type alleles. Is this mutation dominant, recessive, or co-dominant?

co-dominant

At the end of DNA replication, the sister chromatids are held together by the _______.

cohesins

MPF activity was discovered when cytoplasm from a Xenopus M-phase cell was injected into Xenopus oocytes, inducing the oocytes to form a mitotic spindle. In a control experiment, Xenopus interphase cytoplasm was injected into oocytes and shown not to induce the formation of a mitotic spindle. Which of the following statements is not a legitimate conclusion from the control experiment?

components of an interphase nucleus are insufficient to cause mitotic spindle formation

New plasma membrane reaches the plasma membrane by the [regulated/constitutive] exocytosis pathway. New plasma membrane proteins reach the plasma membrane by the [regulated/constitutive] exocytosis pathway. Insulin is secreted from pancreatic cells by the [regulated/constitutive] exocytosis pathway. The interior of the trans Golgi network is [acidic/alkaline]. Proteins that are constitutively secreted [aggregate/do not aggregate] in the trans Golgi network.

constitutive constitutive regulated acidic do not aggregate

During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in ______________ signaling.

contact-dependent

Which of the following statements about the cytoskeleton is false?

covalent bonds between protein monomers hold together cytoskeletal filaments

The activation of the serine/threonine protein kinase Akt requires phosphoinositide 3-kinase (PI 3-kinase) to _________.

create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane

Levels of Cdk activity change during the cell cycle, in part, because ________________.

cyclin levels change during the cycle

The ______ makes up about half of the total cell volume of a typical eukaryotic cell. Ingested materials within the cell will pass through a series of compartments called ______ on their way to the ______________, which contains digestive enzymes and will ultimately degrade the particles and macromolecules taken into the cell and will also degrade worn-out organelles. The __________ has a cis and trans face and receives proteins and lipids from the ________, a system of interconnected sacs and tubes of membranes that typically extends throughout the cell.

cytosol endosomes lysosome golgi apparatus endoplasmic reticulum

You are working for a biotech company that has discovered a small-molecule drug called H5434. H5434 binds to LDL receptors when they are bound to cholesterol. H5434 binding does not alter the conformation of the LDL receptor's intracellular domain. Interestingly, in vitro experiments demonstrate that addition of H5434 increases the affinity of LDL for cholesterol and prevents cholesterol from dissociating from the LDL receptor even in acidic conditions. Which of the following is a reasonable prediction of what may happen when you add H5434 to cells?

cytosolic cholesterol levels will decrease relative to normal cells

For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______.

decreasing the binding strength between subunits on filaments

Which of the following mechanisms is not directly involved in inactivating an activated RTK?

dephosphorylation by serine/threonine phosphatases

Consider the mechanism by which actin and tubulin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules?

depolymerization initiates at the plus ends of filaments

The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by ________________.

diffusing into cells and stimulating the cyclase directly

A cell with nuclear lamins that cannot be phosphorylated in M phase will be unable to ________________.

disassemble its nuclear lamina at prometaphase

Which of the following statements is false? (signaling)

dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids

Which of the following statements about disulfide bond formation is false?

disulfide bonds form spontaneously within the Er because the lumen of the ER is oxidizing

Cells in the G0 state ________________.

do not divide

Which of the following statements about meiosis is true?

during meiosis, the paternal chromosomes pair with the maternal chromosomes before lining up at the metaphase plate

During sexual reproduction, novel mixtures of alleles are generated. This is because _______.

during meiosis, the segregation of homologs is random such that different gametes end up with different alleles of each gene

Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but wasn't listening carefully when he was told about the molecular defect of this cell line. He's too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits but vesicle budding and the removal of coat proteins don't happen. Which of the following proteins might be lacking in this cell line?

dynamin

Which of the statements below about intermediate filaments is false?

each filament is about 10 um in diameter

Many features of __________________ cells make them suitable for biochemical studies of the cell-cycle control system. For example, the cells are unusually large and are arrested in a __________________-like phase. When the cells are triggered to resume cycling, the cell divisions have especially __________________ G1 and G2 phases and occur __________________. Studies with Xenopus eggs identified a partly purified activity called __________________ that drives a resting Xenopus oocyte into M phase. MPF activity was found to __________________ during the cell cycle, although the amount of its kinase component, called __________________, remained constant. The regulatory component of MPF, called __________________, has a __________________ effect on MPF activity and plays a part in regulating interactions with its __________________s. The components of MPF are evolutionarily __________________ from yeast to humans, so that the corresponding human genes are __________________ to function in yeast.

egg G2 short synchronously maturation promoting factor oscillate Cdk cyclin stimulatory substrates cnserved able

Signal sequences that direct proteins to the correct compartment are ______.

encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination

Cells can signal to each other in various ways. A signal that must be relayed to the entire body is most efficiently sent by __________________ cells, which produce hormones that are carried throughout the body through the bloodstream. On the other hand, __________________ methods of cell signaling do not require the release of a secreted molecule and are used for very localized signaling events. During __________________ signaling, the signal remains in the neighborhood of the secreting cell and thus acts as a local mediator on nearby cells. Finally, __________________ signaling converts electrical impulses into a chemical signal. Cells receive signals through a __________________, which can be an integral membrane protein or can reside inside the cell.

endocrine contact-dependent paracrine neuromal receptor

Plasma membrane proteins are inserted into the membrane in the _______. The address information for protein sorting in a eukaryotic cell is contained in the _______ of the proteins. Proteins enter the nucleus in their ______ form. Proteins that remain in the cytosol do not contain a ________. Proteins are transported into the Golgi apparatus via _________. The proteins transported into the endoplasmic reticulum by _______ are in their ________ form.

endoplasmic reticulum amino acid sequence folded sorting signal transport vesicles protein translocators unfolded

Which of the following statements is true? (Signal Molecules)

extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior

Mitogens are _____.

extracellular signals that stimulate cell division

The concentration of mitotic cyclin (M cyclin) ________.

falls toward the end of M phase as a result of ubiquitylation and degredation

Intermediate filaments help protect animal cells from mechanical stress because _____.

filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells

To reproduce sexually, an organism must create haploid ________ cells, or __________, from diploid cells via a specialized cell division called _______. During mating, the father's haploid cells, called _______ in animals, fuse with the mother's haploid cells, called ___________. Cell fusion produces a diploid cell called a ________, which undergoes many rounds of cell division to create the entire body of the new individual. The ells produced from the initial fusion event include _______ cells that form most of the tissues of the body as well as the __________-line cells that give rise to the next generation of progeny.

germ gametes meiosis sperm eggs zygote somatic germ

Which of the following does not occur during M phase in animal cells?

growth of the cell

Intermediate filaments are elongated fibrous proteins with an N-terminal globular _____ region and C-terminal globular _____ region; these regions flank the elongated rod domain. The alpha-helical region of the rod interacts with the alpha-helical region of another monomer in a _____ configuration to form a dimer. _____ dimers will line up to form a staggered tetramer. _____ strands of tetramers come together and twist together to form the _____ nm filament. The _____ domains are exposed on the surface of the intermediate filament, allowing for interaction with cytoplasmic components.

head tail coiled-coil two eight ten globular

Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is false?

heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family

When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________.

hormone

All members of the steroid hormone receptor family ________.

interact with signal molecules that diffuse through the plasma membrane

Foreign substances like nicotine, morphine, and menthol exert their initial effects by ________.

interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus

The G1 DNA damage checkpoint ___________.

involves the inhibition of cyclin-Cdk complexes by p21

Name the three main classes of cell-surface receptors.

ion-channel-coupled receptors G-protein-coupled receptors enzyme-coupled receptors

A protein kinase can act as an integrating device in signaling if it ______.

is activated by two or more proteins in different signaling pathways

What is the role of the nuclear localization sequence in a nuclear protein?

it is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore

Which of the following statements about the anaphase-promoting complex (APC) is false?

it is continuously active throughout the cell cycle

Intermediate filaments are found mainly in cells that are subject to mechanical stress. Gene mutations that disrupt intermediate filaments cause some rare human genetic diseases. For example, the skin of people with epidermolysis bullosa simplex is very susceptible to mechanical injury; people with this disorder have mutations in their _________ genes, which code for the intermediate filament found in epithelial cells. These filaments are usually connected from cell to cell through junctions called _________s. The main filaments found in muscle cells belong to the _______ family; people with disruptions in these intermediate filaments can have muscular dystrophy. In the nervous system, _______s help strengthen the extremely long extensions often present in nerve cell axons; disruptions in these intermediate filaments can lead to neurodegeneration. People who carry mutations in the gene for ______, an important protein for cross-linking intermediate filaments, have a disease that combines symptoms of epidermolysis bullosa simplex, muscular dystrophy, and nuerodegeneration. Humans with progeria, a disease that causes premature aging, carry mutations in nuclear _______.

keratin desmosomes vimentin neurofilament plectin lamin

Which of the following statements about kinetochores is true?

kinetochores assemble onto chromosomes during late prophase

Somatic cells ________.

leave no progeny

Ca2+ can trigger biological effects in cells because an unstimulated cell has an extremely __________________ concentration of free Ca2+ in the cytosol, compared with its concentration in the __________________ space and in the __________________, creating a steep electrochemical gradient. When Ca2+ enters the cytosol, it interacts with Ca2+-responsive proteins such as __________________, which also binds diacylglycerol, and __________________, which activates CaM-kinases.

low extracellular endoplasmic reticulum protein kinase C calmodulin

Which of the following statements most correctly describes meiosis?

meiosis involves a single round of DNA replication followed by two successive cell divisions

Which of the following statements about the function of the centrosome is false?

microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome

Which of the following organelles is not part of the endomembrane system?

mitochondria

Haplotype blocks can be seen in humans because _______.

modern humans descended from a relatively small population of about 10,000 individuals that existed about two thousand generations ago

Which of the following statements about peroxisomes is false?

most peroxisomal proteins are synthesized in the ER

Which of the following statements about microtubules is true?

motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament

Which of the following statements is false? (cytokinesis - motor proteins)

motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall

Disassembly of the nuclear envelope ________.

must occur for kinetochore microtubules to form in animal cells

Which of the following statements is false? (Sex)

mutations in somatic cells are passed on to individuals of the next generation

Your friend works in a biotech company that has just discovered a drug that seems to promote lamellipodia formation in cells. Which of the following molecules is unlikely to be involved in the pathway that this drug affects?

myosin

In mammals, there are two sex chromosomes, X and Y, which behave like homologous chromosomes during meiosis. Normal males have one X chromosome and one Y chromosome, and normal females have two X chromosomes. Males with an extra Y chromosome (XYY) are found occasionally. Which of the following could give rise to such an XYY male? Explain your answer.

nondisjunction in the second meiotic division of spermatogenesis; normal meiosis in the mother

If you crossed the round-seeded plants obtained in the F1 generation with a true-breeding strain of the round-seeded plants, how many wrinkle seeded plants would you expect to obtain in the next generation?

none

You are studying nuclear lamins in yeast. Using recombinant DNA technology, you alter the coding sequence of a nuclear lamination's gene such that the gene now codes for a nuclear lamination's protein that can no longer be phosphorylated when the nuclear envelope is broken down during mitosis. What do you predict would happen if the yeast cell only had the altered nuclear lamination's gene (and not the unaltered version)?

nuclear lamins will no longer disassemble properly during mitosis

Which of the following statements about nuclear transport is true?

nuclear pores have water-filled passages that small, water-soluble molecules can pass through in a nonselective fashion

Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport?

nuclear transport receptors would be unable to release their cargo in the nucleus

Match the type of intermediate filament with its appropriate location. lamins _________ neurofilaments _________ vimentins _________ keratins _________ A. nerve cells B. epithelia C. nucleus D. connective tissue

nucleus nerve cells connective tissue epithelia

Which of the following statements is correct? Kinesins and dyneins _________.

often move in opposite directions to each other

Different glycoproteins can have a diverse array of oligosaccharides. Which of the statements below about this diversity is true?

oligosaccharide diversity comes from modifications that occur in the ER and the Golgi of the 14-sugar oligosaccharide added to the protein in the ER

Which of the following statements about the cell cycle is false?

once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells

You are interested in Fuzzy, a soluble protein that function within the ER lumen. Given that information, which of the following statements must be true?

once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded

Which of the following statements about organellar movement in the cell is false?

only the microtubule cytoskeleton is involved in organellar movement

Which of the following statements about phagocytic cells in animals is false?

phagocytic cells are important in the gut to take up large particles of food

Gregor Mendel studied pea plants and developed some very important ideas about how genes are inherited. These studies used plant strains that were true breeding and always produced progeny that had the same ______ as the parent. These strains were true breeding because they were _______ for the gene important for a specific trait. In other words, for these true breeding strains, bot chromosomes in the diploid pea plant carried the same ________ of the gene. Mendel started out examining the inheritance of a single trait at a time, and then moved on to examining two traits at once in a __________ cross. His studies examining the inheritance of two traits in one cross allowed him to discover what is now known as Mendel's law of _______ assortment. Geneticists can study the inheritance of specific traits in humans by analyzing a ____________, which shows the phenotypes of different family members over several generations for a particular trait.

phenotype homozygous allele dihybrid independent pedigree

Which of the following statements about molecular switches is false?

phosphates remove the phosphate from GTP on GTP-binding proteins, turning them off

Keratins, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments?

phosphorylation causes disassembly during every mitotic cycle

Eukaryotic cells are continually taking up materials from the extracellular space by the process of endocytosis. One type of endocytosis is __________________, which uses __________________ proteins to form small vesicles containing fluids and molecules. After these vesicles have pinched off from the plasma membrane, they will fuse with the __________________, where materials that are taken into the vesicles are sorted. A second type of endocytosis is __________________, which is used to take up large vesicles that can contain microorganisms and cellular debris. Macrophages are especially suited for this process, as they extend __________________ (sheetlike projections of their plasma membrane) to surround the invading microorganisms).

pinocytosis clathrin endosome phagocytosis psuedopods

Figure Q17-57 shows an electron micrograph of a skeletal muscle fiber, where various points along a fiber and various regions have been labeled. Which of the following statements is true about muscle contraction?

point B will move closer to point C

The survival, __________________, and size of each cell in an animal are controlled by extracellular signal molecules secreted by neighboring and distant cells. Many of these signal molecules bind to a cell-surface __________________ and trigger various intracellular signaling pathways. One class of signal molecules, called __________________, stimulates cell division by releasing the molecular brakes that keep cells in the __________________ or __________________ phase of the cell cycle. Members of a second class of signal molecules are called __________________, because they stimulate cell growth and an increase in cell mass. The third class of signal molecules, called __________________, inhibits __________________ by regulating members of the __________________ family of proteins. In addition to such stimulatory factors, some signal proteins such as __________________ act negatively on other cells, inhibiting their survival, growth, or proliferation.

proliferation receptor mitogens G0 G1 growth factors survival factors apoptosis Bcl2 myostatin

Cell movement involves the coordination of many events in the cell. Which of the following phenomena is not required for cell motility?

release of Ca2+ from the sarcoplasmic reticulum

Cytokinesis in animal cells ________.

requires ATP

Which of the following structures shorten muscle contraction?

sarcomeres

Which of the following items is not important for flagellar movement?

sarcoplasmic reticulum

Proteins are transported out of a cell via the __________________ or __________________ pathway. Fluids and macromolecules are transported into the cell via the __________________ pathway. All proteins being transported out of the cell pass through the __________________ and the __________________. Transport vesicles link organelles of the __________________ system. The formation of __________________ in the endoplasmic reticulum stabilizes protein structure.

secretory exocytic endocytic endoplasmic reticulum golgi apparatus endomembrane disulfide bonds

G-protein coupled receptors (GPCRs) all have a similar structure with __________ transmembrane domains. When a GPCR binds an extracellular signal, an intracellular G protein, composed of _______ subunits, becomes activated. ___________ of the G-protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the alpha subunit is bound to ______, which is exchanged for _______ on stimulation. The intrinsic _______ activity of the alpha subunit is important for inactivating the G protein. _______ inhibits this activity of the alpha subunit, thereby keeping the subunit in an active state.

seven three two GDP GTP GTPase Cholera toxin

Which of the following statements about the benefits of sexual reproduction is false?

sexual reproduction permits enhanced survival because the gametes that carry alleles enhancing survival in harsh environments are used preferentially during fertilization

Which of the following statements about a protein in the lumen of the ER is false?

some of the proteins in the lumen of the ER can end up in the plasma membrane

A large protein that passes through the nuclear pore must have an appropriate _______.

sorting sequence, which typically contains the positively charged amino acid lysine and arginine

The microtubules in a cell form a structural framework that can have all the following functions except which one?

strengthening the plasma membrane

Which of the following statements about genome-wide association studies (GWAS) is false?

studies using GWAS only examine SNPs that occur very rarely (<0.001%) in the population, as those SNPs are most likely to cause disease

Figure Q15-34 shows the organization of a protein that normally resides in the plasma membrane. The boxes labeled 1 and 2 represent membrane-spanning sequences and the arrow represents a site of action of signal peptidase. Given this diagram, which of the following statements must be true?

the C-terminus of this protein is cytoplasmic

Which of the following statements about vesicular membrane fusion is false?

the GTP hydrolysis of the Rabbles proteins provides the energy for membrane fusion

The length of time a G protein will signal is determined by _______.

the GTPase activity of Galpha

Which of the following statements is false? (Cdk)

the activating phosphatase (Cdc25) removes all phosphates from mitotic Cdk so that M-Cdk will be active

Which of the following events does not usually occur during interphase?

the nuclear envelope breaks down

N-linked oligosaccharides on secreted glycoproteins are attached to __________________.

the asparagine in the sequence Asn-X-Ser/Thr

Progression through the cell cycle requires a cyclin to bind to a Cdk because _________.

the binding of a cyclin to Cdk is required for Cdk enzymatic activity

Microtubules are important for transporting cargo in nerve cell axons, as diagrammed in Figure Q17-33. Notice the two types of cargo are traveling in opposite directions Which of the following statements is likely to be false?

the black cargo and the gray cargo are moving along microtubules of opposite polarity

Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2?

the cell would enter M phase under conditions when normal cells would not

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only?

the cells produced would get smaller and smaller

When Ras is activated, cells will divide. A dominant-negative form of Ras clings too tightly to GDP. You introduce a dominant-negative form of Ras into cells that also have a normal version of Ras. Which of the following statements is true?

the cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate Ras

All intermediate filaments are of similar diameter because ____________.

the central rod domains are similar in size and amino acid sequence

Which of the following statements about skeletal muscle contraction is false?

the changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an inflict of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction

Which of the following statements is false? (cytokinesis)

the cleavage furrow always forms in the middle of the cell

Proteins that are fully translated in the cytosol and lack a sorting signal will end up in ______.

the cytosol

Which of the following statements about G-protein-coupled receptors (GPCRs) is false?

the different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains

Which of the following statements about actin is false?

the dynamic instability of actin filaments is important for cell movement

Activated protein kinase C (PKC) can lead to the modification of the membrane lipids in the vicinity of the active PKC. Figure Q16-38 shows how G proteins can indirectly activate PKC. You have discovered the enzyme activated by PKC that mediates the lipid modification. You call the enzyme Rafty, activated it to modify the plasma membrane lipids in the vicinity of the cell where PKC is active; these lipid modifications can be detected by dyes that bind to the modified lipids. Cells lacking Rafty do not have these modifications, even when PKC is active. Which of the following conditions would lead to signal-independent modification of the membrane lipids by Rafty?

the expression of a constitutively active phospholipase C

A friend declares that chromosomes are held at the metaphase plate by microtubules that push on each chromosome from opposite sides. Which of the following observations does not support your belief that the microtubules are pulling on the chromosomes?

the jiggling movement of chromosomes at the metaphase plate

Which of the following statements is false? (S Phase)

the loading of the origin recognition complexes (ORCs) is triggered by S-Cdk

Which of the following statements about secretion is true?

the membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior

Which of the following statements is true? (mitotic spindle)

the mitotic spindle helps segregate the chromosomes to the two daughter cells

Which of the following statements regarding dynamic instability is false?

the newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end

Cells have oligosaccharides displayed on their cell surface that are important for cell-cell recognition. Your friend discovered a transmembrane glycoprotein, GP1, on a pathogenic yeast cell that is recognized by human immune cells. He decides to purify large amounts of GP1 by expressing it in bacteria. To his purified protein he then adds a branched 14- sugar oligosaccharide to the asparagine of the only Asn-X-Ser sequence found on GP1 (Figure Q15-48). Unfortunately, immune cells do not seem to recognize this synthesized glycoprotein. Which of the following statements is a likely explanation for this problem?

the oligosaccharide needs to be further modified before it is mature

Which of the following statements is true? (signaling)

the regulation of inflammatory responses at the site of an infection is an example of paracrine signaling

Which of the following reasons was essential for Mendel to disprove the theory of blended inheritance?

the traits that Mendel examined involved an allele that was dominant and an allele that was recessive

There are organisms that go through meiosis but do not undergo recombination when forming haploid gametes. Which of the following statements correctly describes the gametes produced by such an organism. (Assume that these organisms are diploid, that each of the two homologous chromosomes are genetically distinct as typically found in the wild, and that these organisms have more than one chromosome.)

this organism could potentially produce 2n genetically distinct gametes, where n is its haploid number of chromosomes

Proteins that are fully translated in the cytosol do not end up in ______.

transport vesicles

Starting with a single diploid cell, mitosis produces [two/four] [identical/different] [haploid/diploid] cells, whereas meiosis yields [two/four] [identical/different] [haploid/diploid] cells. This is accomplished in meiosis because a single round of chromosome [replication/segregation] is following by two sequential rounds of [replication/segregation]. Mitosis is more like meiosis [I/II] than meiosis [I/II]. In meiosis I, the kinetochores on sister chromatids behave [independently/coordinately] and this attach to microtubules from the [same/opposite] spindle. The cohesion-mediated glue between [chromatids/homologs] is regulated differently near the centromeres than along the chromosome arms. Cohesion is lost first at the [centromeres/arms] to allow segregation of [chromatids/homologs] and is lost later at the [centromeres/arms] to trigger segregation of [chromatids/homologs].

two identical diploid four different haploid replication segregation II I coordinately same chromatids arms homologs centromeres chromatids

Imagine meiosis in a diploid organism that only has a single chromosome. Like most diploid organisms, it received one copy of this chromosome from each of its parents and the two homologs are genetically distinct. If only a single homologous recombination event occurs during meiosis, which of the following choices below correctly describes the four gametes formed.

two of the gametes will have chromosomes identical to the chromosomes found in the original diploid cell, while two of the gametes will have chromosomes that are different

Organisms that reproduce sexually ___________.

undergo a sexual reproductive cycle that involves an alternation of haploid cells with the generation of diploid cells

Both budding yeast and the bacteria E. coli are unicellular life. Which of the following statements explains why budding yeast can undergo sexual reproduction while E. coli cannot.

unlike E. coli, budding yeast can alternate between a diploid state and a haploid state

Which of the following does not describe a situation of asexual reproduction?

using in vitro fertilization to combine a sperm and an egg to create an embryo

Which of the following statements about the round-seeded pea plants obtained in the F2 generation is false?

we expect 25% of these plants to be homozygous for the seed-shape allele

Figure Q15-57 shows the orientation of the Krt1 protein on the membrane of a Golgi-derived vesicle that will fuse with the plasma membrane. Given this diagram, which of the following statements is true?

when this vesicle fuses with the plasma membrane, the N-terminus of Krt1 will be in the extracellular space

An individual transport vesicle _______.

will fuse with only one type of membrane

A single nondisjunction event during meiosis ________.

will involve the production of two normal gametes if it occurs during meiosis II

Which of the following is not good direct evidence that the cell-cycle control system is conserved through billions of years of divergent evolution?

yeast cells have only one Cdk, whereas humans have many Cdks