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34 Cards in this Set

  • Front
  • Back
Cells do not pass from G1 into M phase of the cell cycle unless there are sufficient nutrients to complete an entire cell cycle.
False: There is no G1 to M phase transition. The statement is correct, however, for the G1 to S phase transition, where cells commit themselves to a division cycle.
Apoptosis is mediated by special intracellular proteases, one of which cleaves nuclear lamins.
True: Apoptosis is an active process carried out by special proteases(caspases)
Developing neurons compete for limited amounts of survival factors
True: This mechanism id thought to adjust the number of neurons to the number of specific target cells to which the neurons connect.
Some vertebrate cell-cycle control proteins function when expressed in yeast cells.
True: An amazing evolutionary conservation
It is possible to study yeast mutants that are defective in cell-cycle control proteins, despite the fact that these proteins are essential for the cells to live.
True: Such studies employ so-called conditional mutations, which lead to the production of proteins that usually are atabel and functional at one temperature but unstable or inactive at another temperature. Cells can be grown at the temperature at which the mutant protein functions normal, ant then can be shifted to a temperature at which the protein's function is lost
Both the presence of a bound cyclin an its phosphorylation state determine whether a Cdk protein is enzymatically active.
True: Association of a Cdk protein with a cyclin is required for its activity (hence its name Cyclin-dependent-kinase). Furthermore, phosphorylation at specific sites and dephosphorylation at other sites on the Cdk protein are required for the cyclin-Cdk complex to be active
What do you suppose happens in mutant cell that
A.cannot degrade cyclins
B.always express high levels of p21
C. cannot phosphorylate Rb
All three of mutant cells would be unable to divide. The cells

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 genes regulatory proteins would be constantly inhibited by unphosphorylated Rb
Centormeres are replicated independently of chromosomes.
True: Cnetrosomes replicate during interphase, before M phase begins. The mechanism by which on centrosome gives rise to two, and only two, centrosomes is unknown
The nuclear envelope becomes fragmented at mitosis. It is thus distributed btw daughter cells like other membrane-enclosed organelles such as the endoplasmic reticulum and the Golgi Apparatus
True: In fact, the nuclear envelope is continuous with the ER membrane (discussed in Chp15, and some of the fragments therefore contain membrane derived from both origins.
Two sister chromatids arise by replication of the DNA of the same Chromosome and remain paired as they line up in the metaphase plate
True: Sister chromatids separate only at the start of anaphase.
interpolar microtubules attach end-to-end and are therefore continuous from one spindle pole to the other
False: The ends of interpolar micortubules overlap and attach to one another via proteins (including motor proteins)that bridge btw the microtubules.
Microtubule polymerization and depolymerization and microtubule motor proteins are all required for DNA replicaiton
False: Microtubles and their motor proteins play not role in DNA replication.
Micortubules nucleate at the centromeres and then connect to the Kinetochores, which are structures at the centrosome regions of chromosomes.
False: To be a correct statement, the terms "centromere" and "centrosome" must be switched.
What is the order in which the following events occur during cell Division:

anaphase
metaphase
prometaphase
telophase
lunar phase
mitosis
prophase
where does cytokineis fit in?
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
All five of these steps are referred to as mitosis. There is no lunar phase. Cytokinesis is the last step in M phase, which overlaps with anaphase and telophase. Mitosis and cytokinesis are both part of M phase.
Sketch the principal stages of mitosis. Mark on sister chromatid and follow it through mitosis and cytokinesis. What event commits this chromatid to a particular daughter cell? Once intially committed, can its fate be reversed? What may influence this commitment?
The sister chromatid becomes committed when a microtubule form one od the spindle poles attaches to the kinecochore of the chromatid. Microtublues attachments is sitll reversible until a second micortubule forn the other spindle pole attaches to the kinetichore of its partner sister chromatid so that the duplicated chromosome is now put under mechanical tension by pulling forces form both poles. The tension ensures that both microtubules remain attached to ehte chromosome in the cell at the time the nuclear envelope breaks down will influence which spindle pole the chromatid will be pulled to, as a kinetochore is most likely to become attached to the spindle pole toward which it is facing
In the eukaryotic cell cycle, DNA replicaiton occurs during___1_______, nuclear and cytoplasmic division occur during___2_______, and cell growth occurs during_______3____. In a typical somatic cell,_________4____is the longest phase of the cell cycle.
1.S phase
2. Cytokinesis
3. ?
4. ?
The mitotic spindle is composed mainly of actin filaments
False: The spindle is composed of microtubules and the various proteins that interact with them, including microtubule-dependent motor proteins.
The mitotic spindle assembles during late mitosis
False: The mitotic spindle assembles in early mitosis which means Prophase.
Drugs that cause tubulin depolymerization will inhibit progression through the cell cycle in eucaryote and prokaryote cells/
? Ask someone.
Cytokinesis is achieved by a ring of microtubules that forms on the inner surface of the plasma membrane.
False: It is achieved by a ring of myosin and actin filaments
The contractile ring is formed only in animal cells.
True
Which of the following structures break into fragments prior to cell division?

mitochondria
nuclear membrane
centrosomes
lysosomes
ribosomes
chloroplasts
endoplasmic reticulum
nuclear envelope
List the six stages of M phase of the cell cycle in the order in which they occur.
Prophase
Prometaphase
Metapahse
Anaphase
Telophase
Cytokensis
In cell that has eight chromosomes(four pairs of homologous chromosomes) in G1 phase, how many kinetochores will be present in the cell at mitotic prophase?
8; each duplicated chromosome therefore has tow kinechores (one on each sister chromatid), which face in opposite directions
How many kinetochores will be present in the daughter of such a cell at prophase of the second meiotic division?
16
A kinetochore often binds to more than one microtubule
True: Multiple microtubules are attached to each kinetochore.
They contain DNA-binding proteins that recognize sequences at the telomere of the chromosome
Ask a friend
Kinetochore proteins bind to the tubulin molecules at the very tip of the plus end of microtubules.
True: Kinetochore microtubules bind by their plus ends.
Kinetochores assemble on chromosomes that lack centromeres
False: Kinetochore assembly depends on the presence of the centromere DNA sequence.
Kinetochores bind the polar microtubules, converting them to kinetochore microtubules
True: As a person about it.
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 best supports your belief that microtubules are pulling on the chromosomes, not pushing them?
Ask another person about that.
Which of the following precede re-formation of the nuclear envelope during M phase?

a. formation of the contractile ring
b. decondensation of chromosomes
c. reassmbly of the nuclear lamina
d. formation of the phragmoplast
e. transcription from chromosomes
d. formation of the phragmoblast
Cytokinesis in animal cells

a. requires ATP
b. Leaves a small circular scar of actin filaments on the inner surface of the plasma memebrane
c. is often followed by phosphorylation of integrins in the cell's plasma membrane
d. is generally accompanied by rearrangement of filaments making up the cell cortex
e. is assisted by motor proteins that pull on microtubules attached to the cell cortex
c. is often followed by phosphorylation of integrins in the cell's plasma memebrane
Cytokinesis in plant cells:

a. does not involve a contractil ring
b. does not require ATp
c. always occurs perpendicular to the long axis of the mitotic spindle
d. involves formation of the phragmoplast, a disclike membrane-bound structure containing polysaccharides and glycoproteins
e. results in increasingly smaller daughter callw with each successive round of the cell cycle.
a. does not involve a contractile ring.