CELL BIO EXAM 1-3 QUESTIONS

if DNA is damaged or incompletely replicated in S phase, the inhibition of which of these molecules prevents the cell from entering M phase?

Cdc25

the activation of S-Cdk initiates

DNA replication

which of the following processes occurs only in the S phase of the cell cycle?

DNA replication

which one of the following can give rise to cancer-promoting mutations?

DNA replication errors inhalation of tobacco smoke exposure to ionizing radiation exposure to excess sunlight

the activation of S-Cdk helps prevent

DNA replication occurring more than once each cycle

which of the following correctly matches the phase of the eukaryotic cell cycle with an event that takes place in that phase?

M phase ---- cytokinesis

DNA replication occurs only in the

S phase

how do SNPs differ from mutations?

SNPs are more common in a population

what is the difference between a malignant and benign tumor?

a malignant tumor invades and colonizes other tissues, while a benign tumor does not

which of the following statements are true?

activated G1-Cdks and G1/S-Cdks help drive cells through G1 into S phase activated S-Cdk initiates DNA replication

which of the following statement is false?

activated M-Cdk triggers the onset of cytokinesis this is false because the activated M-Cdk triggers entry into M phase, where the replicated chromosomes will be distributed into two daughter cells

Cdk activity is regulated in several ways.

active: Cdk bound to cyclin, threonine in T loop phosphorylated inactive: Cdk/cyclin bound to p27, T loop in active site, Cdk alone

which type of epithelial cell junction plays a major role in an epithelial sheets ability to develop tension and change its shape?

adherens junction

what is the best description of connective tissue?

all of its cells are sparsely distributed in the extracellular matrix

based on Gregor Mendel's experimentation, yellow peas were assigned the allele genotype symbol uppercase "Y" and green peas were assigned the allele genotype symbol lowercase "y." the progeny of a true-breeding plant with yellow peas YY and one with green peas yy will have which of the following?

all yellow peas only

which of the following is the term for variant versions of a gene?

alleles

gap junctions

allow an electrical and a metabolic coupling between attached cells allow inorganic ions to move directly between attached cells they can open or close as needed allow the cytoplasm of two adjacent cells to be continuous with each other

what does the spindle assembly checkpoint, which blocks the initiation of anaphase until all chromosomes are properly attached to the mitotic spindle, depend on?

an inhibitory signal produced by inappropriately attached chromosomes

the cell-cycle control system monitors the tension on the kinetochores to ensure that ___

anaphase does not occur until the sister chromatids are correctly attached to the spindle

the cell-cycle control system monitors the tensions on the kinetochores to ensure that

anaphase does not occur until the sister chromatids are correctly attached to the spindle

the cell-cycle control system uses Cdk inhibitory proteins to do what?

arrest the cell cycle at specific transition points

what are main functions of the kinetochore?

attaching the sister chromatids to the dynamically growing and shrinking microtubules sensing tension when sister chromatids are attached to opposite poles of the spindle

what are the main functions of the kinetochore?

attaching the sister chromatids to the dynamically growing and shrinking microtubules sensing tension when sister chromatids are attached to opposite poles of the spindle

the loss of its cyclin causes a Cdk to do what?

become inactive

what gives the plant cell wall its tensile strength?

cellulose

in animal connective tissues, tensile strength is chiefly provided by which one of the following?

collagen fibrils and fibers

cyclins vary in

concentration at different stages of the cell cycle

which of the following animal tissues is characterized by a plentiful extracellular matrix?

connective

stem cells hold great promise both for studying cell fate determination and organ development and for clinical use, such as blood stem cell transplants to treat patients whose own immune systems have been severely impaired. clinicians also hope that stem cells can be coaxed into specific cell types to treat diseases in which that cell type is damaged, such as replacing neurons in Parkinson's disease. in 2008, researchers assessed the ability of neurons derived from reprogrammed fibroblasts to ameliorate the symptoms of Parkinson's disease in a rat model. based on your knowledge of stem cells and cell differentiation, what intermediate step was necessary to convert fibroblasts into neurons?

converting fibroblasts into induced pluripotent stem cells

the expression levels of different ___ fluctuate throughout the cell cycle

cyclins

which of the following is false?

cyclins help activate Cdks by phosphorylating them

which of the following could cause the cell to prematurely enter anaphase and the sister chromatids to separate?

defect in the spindle assembly checkpoint

cyclins are

degraded at specific timed in the cell cycle

what drives the reassembly of the nuclear envelope?

dephosphorylation of claims lamins, which are phosphorylated and disassembled by the mitotic Cdk, are dephosphorylated in telophase and can reassemble the nuclear envelope

the reassembly of the nuclear envelop at telophase depends on which of the following?

dephosphorylation of nuclear lamina and nuclear pore proteins - this triggers the breakdown of the nuclear envelope and desphosphorylation allows these proteins to reassemble and the nuclear envelope and lamina to reform

which of the following animal cell types, under appropriate conditions, can be kept proliferating indefinitely in culture and yet retain unrestricted developmental potential?

embryonic stem cells

cell-cycle control system

ensures that all DNA is replicated before M phase begins ensures that all chromosomes are attached to the mitotic spindle before the chromosomes are segregated to the two daughter cells ensures that the environment is favorable for the cell to initiate DNA replication

cyclins have no

enzymatic activity on their own

the inactivation of M-Cdk leads to which of the following?

exit from mitosis

true or false: a stem cell can only produce a single type of differentiated cell

false

true or false: apoptosis is a form of programmed cell death in which cells kill themselves by migrating to the bloodstream where they are carried to the liver for destruction

false

true or false: during mitosis, most mammalian cells flatten out to prepare for cleavage

false

true or false: survival factors act primarily by stimulating cell division

false

a fibroblast can attach indirectly to collagen via which type of extracellular matrix protein?

fibronectin - provides a linkage between the cell and collagen; part of the fibronectine molecule binds to collagen, while another part forms an attachment site for integrins

mendel crossed true-breeding plants producing yellow peas with true-breeding plants producing green peas, and found that the hybrid of offspring all had yellow peas. which allele is recessive?

green pea allele

mendel chose to study traits that are inherited in a discrete fashion. what does this mean?

he studied traits that did not become "blended" in subsequent generations

what attaches epithelial cells to the basal lamina?

hemidesmosomes

if the cell is deprived of mitogens for a prolonged period of time, it will enter a non-proliferating state in which it may remain for how long?

hours, days, weeks, the remaining lifetime cells can withdraw from the cell cycle for prolonged periods, either temporarily or permanently

Rb is an important protein for controlling cell proliferation by blocking entry into S phase. how does it exert its effect?

in its unphosphorylated state, Rb is active and blocks transcriptional regulators

which term best describes the process by which maternal and paternal chromosomes are shuffled and distributed randomly during meiosis 1?

independent assortment - the resulting gametes will receive novel assortments of maternal and paternal alleles

some cancer cells are missing a key protein needed to repair double-strand DNA breaks. they survive by relying on alternative DNA repair mechanisms. to treat these cancers, researchers have developed drugs that do which of the following?

inhibit alternative DNA repair mechanisms

which type of protein in a fibroblast's plasma membrane attaches to the extracellular matrix on the outside of the cell and (through adapter molecules) to actin inside the cell?

integrin

in desmosomes, cadherin molecules are anchored inside an epithelial cell to which type of cytoskeletal filament?

intermediate filaments

the entire period between one M phase and the subsequent M phase is called what?

interphase

which of the following statements about the cell-cycle control system is not true?

it ensures that M phase is completed before cytokinesis begins but, cytokinesis is part of M phase

what is true of the basic organization and machinery of the cell cycle?

it is essentially the same in all eukaryotes

what must happen for a Cdk to be active?

it must bind to its cyclin partner

which of the following mutations is not typically found in a genetic screen?

lethal mutations

why is loop 2 important for p53 function?

loop 2 helps position a critical arginine for binding DNA

which two processes together constitute the M phase of the cell cycle?

mitosis and cytokinesis

in most cases, how many mutations are required for a normal cell to turn into a cancer cell?

more than 3

when a cell is actually injured, it usually dies by which process?

necrosis

many of the genes mutated in individual tumors are involved with which of the following regulatory pathways?

pathways regulating the cell's response to DNA damage or stress pathways governing the initiation of cell division

which of the following are the plant equivalent of a gap junction?

plasmodesmata - they are cytoplasmic channels, lines with plasma membrane, that penetrate cell walls to connect neighboring plant cells

sexual reproduction generates genetic diversity by which processes?

production of novel allele combinations genetic recombination

5 stages of mitosis in order

prophase, prometaphase, metaphase, anaphase, telophase

why does the nuclear envelope break down at the start of prometaphase?

proteins that form the nuclear pores and nuclear lamina become phosphorylated

why does the nuclear envelope break down at the start of prometaphase?

proteins that form the nuclear pores and nuclear lamina becomes phosphorylated

which cancer causing gene can be activated by a single mutation in only one allele?

proto-oncogene

which method is the best way for identifying rare, large-effect mutations?

sequencing the exons of affected individuals, as well as their parent and sibilings

attachment of sister chromatid pairs to opposite poles of the spindle creates tension in the kinetochores, which ____

signals that the sister chromatids are ready to be separated

each sister chromatid in a pair must attach to the opposite pole of the spindle for the

sister chromatids to be segregated properly

which of the following occurs at specific times in the cell cycle?

some cyclins are ubiquitylated and degraded in proteasomes

Cdk inhibitors inhibit the function of cyclin-dependent protein kinases. different inhibitors display varying mechanisms of Cdk inhibition. which of the following might a Cdk inhibitor block in order to block Cdk function?

substrate binding ATP binding cyclin binding

which of the following is true of the basal lamina

supports epithelial cells by interacting with integrals in the basal plasma membrane thin, though sheet of extracellular matrix contains a specialized type of collagen type IV

attachment of sister chromatid pairs to opposite poles of the spindle creates

tension in the kinetochores, which signals that the sister chromatids are ready to be separated

what accounts for the difference in the curve shapes depicting concentration of M-cyclin versus M-Cdk activity during the cell cycle?

the M-Cdk complex is not activated until M-cyclin is bound and M-Cdk is dephosphorylated

which of the following statements about S-Cdk is false?

the activation of S-Cdk helps prevent the onset of M phase

which of the following is not true of the basal lamina?

the basal lamina lines the cytosolic side of the epithelial cell's basal plasma membrane

if a chromosome is attached to two microtubules from opposite poles and one of the microtubules is experimentally severed, what occurs?

the chromosomes migrates quickly to the pole to which it is still attached

which feature of glycosaminoglycans (GAGs) allows the extracellular matrix in cartilage to resist compression?

the negative charges on GAGs attract sodium ions, which draw water into the extracellular matrix to form a water-filled gel

which of the following statements is false?

the pairing of homologous chromosomes during prometaphase is called bi-orientation rather, the attachment of duplicated chromosomes, or sister chromatids, to microtubules from opposite spindle poles is called bi-orientation

which of the following statements about cells in G0 is false?

their cell-cycle control system is dismantled irreversibly

which of the following is inconsistent with the function of gap junctions?

they allow ATP-driven pumps to move substances between attached cells

what is true of induced pluripotent stem (iPS) cells?

they behave like embryonic stem cells

which of the following statements about cells in G0 is true?

they can be stimulated to proliferate if the surrounding tissue is damaged they can divide if the need arises but normally do so infrequently they retain the ability to reassemble the cell-cycle control system

what is true of cadherin proteins?

they link epithelial cells together by binding to similar cadherins in adjacent epithelial cells

which of the following statements described how growth factors stimulate animal cell enlargement?

they stimulate intracellular protein synthesis

epithelial cells line body cavities and, in organs like the intestine, separate the extracellular environment (intestinal lumen) from the body. the barrier function of epithelial tissues is important for maintaining homeostasis and preventing infections from gut-associated microbiota and viruses. some bacteria and viruses compromise this barrier function, aiding their pathogenesis. which of the following structures, most critical to the barrier function of epithelial tissue, is targeted by these infectious agents?

tight junctions

which epithelial cell junctions serve to seal neighboring cells together so that water-soluble molecules cannot easily leak between them?

tight junctions - seal neighboring cells together so that water-soluble molecules cannot easily lead between them

which of the following is responsible for the most cancer cases?

tobacco smoke

true or false: even perfectly healthy cells may undergo apoptosis

true

true or false: in the presence of severe DNA damage, the transcription regulator p53 can promote cell death.

true

true or false: many cells in normal animal tissues require extracellular signals from other cells to avoid apoptosis. this could be a mechanism for ensuring that cells survive only when and where they are needed.

true

true or false: most cases of cervical cancer are caused by a viral infection

true

true or false: protons-oncogenes can play an important role in controlling the division of normal cells

true

true or false: the rate of cell turnover varies in different tissue types

true

the p53 and Tumor Growth animation demonstrates that mice can develop lymphoma in certain tissues lacking p53. suppose different p53 gene sequences were added back to the lymphoma in mice. for each of the following, predict whether the lymphoma in the mice would grow or shrink over time. sort the treatments into the Tumor Growth or Tumor Regression boxes.

tumor growth: add a DNA sequence lacking 90% of the p53 gene, add p53 that does not bind to Zn2+, add p53 with Arg248 altered to alanine tumor regression: add a stable p53 that binds better to DNA than wild-type p53

which class of cancer-critical gene must be inactivated to promote the development of cancer?

tumor suppressor gene