biol 4004 exam 3 T/F

A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell

false

A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell.

false

Apoptosomes are formed in the extrinsic pathway of apoptosis

false

BH3-only proteins bind to and inhibit effector Bcl2 proteins, thus inhibiting apoptosis.

false

Cell in the G0 state cannot re-enter the cell cycle.

false

Closely-spaced epithelial cells generally rely on cell-matrix junctions for resistance to mechanical stress

false

Cofilin preferentially binds to filaments containing ATP-actin, resulting in depolymerization of the actin filaments at the rear of a treadmilling network

false

DNA helicase binds to the ends of chromosomes and unwinds the DNA double helix.

false

Death-inducing signaling complexes (DISC) are formed during the intrinsic pathway of apoptosis.

false

During cell migration, actin filaments undergo rapid depolymerization at the leading edge.

false

Epithelial cells are structurally polarized due to the presence of desmosomes.

false

GTP-caps stabilize the plus ends of actin filaments.

false

Genes with mutated forms that cause genetic instability makeup a subclass of cancer-critical genes called tumor progression genes.

false

Most cancer cells lack the enzyme telomerase.

false

Most cancers are the result of exposure to environmental carcinogens.

false

Myosin II molecules for the bipolar thick filaments found in all types of muscle cells

false

Normal cells will stop dividing once they have covered the culture dish with a single monolayer of cells, a phenomenon known as replicative senescence.

false

Nuclear envelope breakdown occurs during interphase.

false

Oncogenes directly promote cancer by causing unregulated cell proliferation, while tumor suppressor mutations only promote cancer indirectly by causing genetic instability.

false

Proteoglycans attached non-covalently to collagen fibrils via linker proteins to form proteoglycan aggregates.

false

Survival factors inhibit apoptosis by the ubiquitylation of caspases, thereby marking them for degradation in proteasomes.

false

The activity of cyclin-Cdk complexes is inhibited by the action of the kinase Cdc25, which adds two inhibiting phosphates to the Cdk active site.

false

The amplifying proteolytic caspase cascade begins with the self-activation of executioner caspases.

false

The duplication of centrosomes occurs in prophase

false

The intracellular domains of claudins are indirectly linked to intermediate filaments via the anchoring protein talin.

false

The minus ends of kinetochore microtubules are attached to the kinetochores of chromatids by the Ndc80 complex

false

Tumor viruses play a role in the majority of human cancers

false

Two actin protofilaments align in antiparallel formation, and twist around each other to form an actin filament

false

Upon binding of a Fas ligand, the death domain of the Fas death receptor is cleaved by initiator caspases

false

A cell has more DNA during G2 than it did in G1

true

APC/C is a member of the ubiquitin ligase family of enzymes

true

Abnormal regulation of apoptotic programs often occurs in cancer cells.

true

At least half of all human cancers have mutations in p53.

true

Bipolar myosin II filaments associate with actin filaments at the rear of a lamellipodia, carrying out sarcomere-like contractions that gather in the sides of the cell as it moves forward

true

Both laminin and type IV collagen have binding domains for the linkers perlecan and nidogen.

true

Cadherins promote cell-cell interactions by binding to cadherin molecules of the same or closely related subtype on adjacent cells

true

Cancer therapies directed solely at killing rapidly dividing cancer cells may fail to eliminate all of the transformed tumor cells

true

Controlled cell death is an important process in both developing and adult tissues.

true

DNA replication begins at sites scattered at numerous locations on each chromosome called origins of replication.

true

Decoy receptors inhibit extrinsic apoptosis by competing with death receptors for ligand.

true

Defects in lamin A are associated with certain types of progeria, a rare disorder in which children appear to age prematurely

true

Formins promote the formation of unbranched actin filaments.

true

Glycosaminoglycans are the most negatively charged molecules in animals

true

Hepatitis-B and C cause chronic inflammation of the liver (hepatitis) and are implicated in the development of liver cancer.

true

In the absence of apoptotic signals, executioner caspases exist as inactive dimers.

true

Individuals who inherit a defect in DNA repair mechanisms show a strong predisposition to develop cancer.

true

Individuals with only one functional copy of a tumor suppressor gene are more prone to cancer than individuals with two functional copies of a tumor suppressor gene.

true

Inheritable changes in gene expression can occur without any alteration of the cell's DNA sequence.

true

Members of the cadherin family function as the adhesion proteins in both adherens junctions and desmosomes

true

Mitosis and cytokinesis both occur during the M phase of the cell cycle

true

Most carcinogens are also mutagens.

true

S1 fragments are myosin motor domains isolated by the enzymatic digestion of thick filaments.

true

The BH3-only protein Bid links the extrinsic and intrinsic pathways of apoptosis

true

The activity of cytochrome P-450 oxidases in the liver may sometimes convert chemically inert substances into potent carcinogens

true

The apical surface of skin, known as the stratum corneum, is composed of the remnants of dead skin cells and the network of filaggrin-bundled keratin filaments that were contained within those cells

true

The assembly and contraction of the contractile ring is controlled by the small GTPase RhoA.

true

The assembly of pre-RCs is inhibited by Cdk activity (S phase to early mitosis) and stimulated by APC/C activity (late mitosis to early G1)

true

The inactivation of Cdks by the action of APC/C triggers both anaphase and cytokinesis.

true

The surfaces of apoptotic cells undergo chemical changes that mark them for destruction by phagocytic cells

true

The switch between the active and inactive conformations of integrins can be triggered by the binding of a molecule to either the intra- or extra-cellular domains.

true

Tobacco smoke is by far the most important carcinogen.

true

~15% of human cancers are thought to involve viruses, bacteria or parasites.

true

During muscle contraction, thin filaments shorten in length.

False

In the rigor state, ATP-associated myosin heads are tightly bound to an actin filament.

False

The intracellular blocking protein FLIP resembles an executioner caspase but lacks protease activity

False

The intracellular domains of all integrin isoforms bind indirectly to actin filaments.

False

Unlike conventional ion channels, gap junctions are always in an open conformation.

False

Actin filaments form both transient and stable structures.

True

Hyaluronan is a unique GAG containing non-sulfated sugar residues.

True

In healthy adult tissues that are neither growing nor shrinking, cell death and cell division need to be in exact balance.

True

Intermediate filaments strengthen cells against mechanical stress.

True

Mixtures of cells expressing two different cadherins will sort into two aggregates while mixtures of cells expressing different levels of the same cadherin will sort into two layers of the same aggregate.

True

Mutations in nuclear lamin genes cause the skin blistering disease epidermolysis bullosa simplex.

True