Cell Division Flashcards
_____ is the nondividing cell state
G0
The ___ ____ is every other phase, other than the G0 phase. When chromosomes are duplicated and two identical, daughter cells are formed.
Cell cycle
The ___ is the phase when cells decide if they can divide and commit to dividing. The point when cells commit to dividing is called ____ ___.
G1
Restriction point
The ____ phase is when DNA synthesis and replication occurs. This is also the time where the centrosome is duplicated.
S
The ____ phase involves verification that all DNA synthesis has been completed and includes assembling the machinery that will trigger entry into mitosis
G2
The ___ phase also called ___ is when the replicated chromosomes separate into two cells
M
Mitosis
____ refers to the behavior of chromosomes in dividing somatic cells. ____ is a behavior of the entire cell pinching into two daughter cells, and occurs toward the end of mitosis during telophase.
Mitosis
Cytokinesis
Mitosis is divided into five stages:
1.
2.
3.
4.
5.
Prophase, pro metaphase, metaphase, anaphase, and telophase
During ____ the replicated daughter centrosomes move apart, chromosomes begin to condense, and the nuclear envelope breaks down
Prophase
During ____ bipolar spindles become apparent, microtubules attach to kinetichores, and chromosome/nuclear events continue
Prometaphase
During ____ maximally, condensed replicated, chromosomes align in a single plane as a disk like plate
Metaphase
During ______ daughter, chromatids separate from each other, and begin to move apart as individual chromosomes
Anaphase
During _____ the plasma membrane begins to constrict around at the spindle midline, chromosomes begin to decondense, and the nuclear envelope begins to reform
Telophase
______ encompass adjacent daughter chromatids, so that they remain attached to each other throughout G2, prophase, prometaphase, and metaphase. These proteins are proteolyzed at the onset of anaphase to allow the chromatids to segregate into two daughter cells
Cohesions
In prophase, ____ are activated and are responsible for chromosome compaction. They bridge different points along DNA strands to form loops in sequential waves forming loops within loops this process reaches its peak in metaphase.
Condensins
At the onset of Mphase, the duplicated centrioles, split and move apart to form the two poles of the spindle apparatus. Spindle pool movement is driven by ____ involving the motor proteins ___ and ____.
Microtubules
Kinesin
Dynein
The nuclear envelope is broken down when lamin filaments (intermediate filaments) are ____ by ____, causing them to depolymerize
Phosphorylated
Cyclin-dependent kinase (CDK1)
Spindle microtubules include ____ microtubules, ____ microtubules, and ____ microtubules.
Kinetochore
Interpolar
Astral
A ____ is a complex of proteins that assemble on centromeric DNA. they function as attachment points for spindle microtubules. They also sense alignment of chromosomes in metaphase.
Kinetochore
____ is a histone in the kinetochore composition. It defines centromeric chromatin, and mediates binding of kinetochores to DNA.
CENP-A
The ______ complex of Kinetochore permits tubulin polymerization and D polymerization to occur while continuing to maintain microtubule – kinetochore coupling.
Ndc80
The ____ end of the microtubule directs motor proteins to push chromosomes away from the spindle poles
+
_____ of microtubules at the kinetochore pulls chromosomes toward the spindle pole.
Depolymerization
Microtubule ____, where, in tubulin subunits are removed at the ___ end, can also pull microtubules and attach to chromosomes to towards the pole.
_______ is activated at the metaphase – anaphase transition. Cdc20 is an activator of this complex. Together they tag securin for destruction. Securin is an inhibitor of ______ . Activated ____ is released which hydrolyzes cohesin and promotes daughter chromatid separation.
APC/C anaphase promoting complex, a ubiquitin ligase complex
Separase
Separase
In addition to cohesins, the protein _______ helps maintain sister chromosome attachment, particularly in the centromere region, preventing premature separation prior to anaphase
SGO (shugoshin)
During anaphase, there is an initial movement of chromosomes to the ____, due to a net balance of push and pull. Overlapping _____ microtubules push against each other via motor proteins and the spindles elongate. The initial kinetochore and spindle pole mediated movements are referred to as anaphase ___. The subsequent spindle elongation is referred to as anaphase ____.
Poles
Interpolar
A
B
During _____, a Central spindle assembly forms at the overlap of interpolar and astral microtubules. This assembly recruits and activates ______, which re-organizes actin microfilaments to form a contractile ring of actin and myosin under the plasma membrane. Contraction is initiated, pinching the cell into two daughter cells.
Cytokinesis
RhoA
The result of spindle defects in mitosis is usually _____, meaning the daughter cells have an abnormal number of chromosomes
Aneuploidy
Signals from both outside and inside, the cell are integrated to regulate proliferation. ____ ____ provide very strong signals promoting proliferation and get cells past the restriction point. ___ ____ are no longer required past the restrictive point (R).
Growth factors
Growth factors
Cell cycle control systems are generally ____ (on/off) and launch events in an irreversible manner.
Binary
One major cell cycle controller is phosphorylation and dephosphorylation events carried out by _______ _____. Another major cell cycle controller regulated proteolysis which is carried out by ____ and ____ (ubiquitin ligase complexes).
Cyclin-dependent kinases (CDKs)
APC/C
SCF
CDKs are regulated by _____, which lack enzymatic activity, but help control, CDK activity and target selection. ____ are proteins that can inhibit CDK activity.
Cyclins
CKIs cyclin-dependent kinase inhibitors
Different pairs of cyclines/CDKs Drive different stages of the cell cycle. The decision to pass the restriction point involves ______. S phase on set and progression involves cyclines ____ and ____. Entry into M phase involves cyclin ____.
G1-CDK
G1/S-CDK and S-CDK
M-CDK
Most ____ are destroyed at the end of the preceding phase via a ubiquitin ligase complex, therefore the first part of G1 is a period with very low ____ activity.
Cyclines
CDK
Growth factors and other signals, as well as lack of DNA damage, trigger the synthesis of _____ __, which then promotes the activation of ____. This further activates more transcription factors that drive the expression of proteins that push the cell through ____.
Cyclin D
G1 CDK
R
Another process that pushes the cell past R is the Ubiquitin ligase complex, ____, which triggers the destruction of ___ ____, removing this potential inhibition to full CDK activation.
SCF
G1 CKIs
Cyclin _____ induces gene transcription for cyclin ____ and ____, which together with CDK2 push a cell into and through S phase respectively.
D
E
A
Growth factor mitogen binds to the tyrosine kinase family of growth factor receptors, _____. This activates Ras G proteins which then activates the ____ ____ pathway.
RTKs
MAP kinase (MAPK)
The MAP kinase pathway consists of three sequential kinases that function as a cascade. ______ phosphorylates _____, which phosphorylates ____.
MAPKKK
MAPKK
MAPK
activated MAPK enters the _____ and phosphorylates and activates transcriptional regulators that are associated with immediate response genes comprising a first wave of transcriptional response
Nucleus
The immediate response genes in the first wave, encode more transcription factors and regulators that produce a ____ _____ of transcription, producing delayed response gene products important in cell cycle advancement including cyclin D.
Second wave
Cyclin D binds to CDK2, forming G1-CDK, which triggers a ___ ____ of gene expression by phosphorylating and inhibiting the _____ protein. This protein is an inhibitor of the _____ family of transcription factors. These transcription factors are then activated. proteins needed for DNA replication and entry into S phase, including cyclin ____ and ___ are produced.
Third wave
Retinoblastoma (pRb)
E2F
E
A
In early G1, Mcm helicases are loaded onto origin recognition complexes ____ by accessory proteins, _____ the ORCs to become active later in S phase. Mcm helicases can only bind and license ORCs under conditions of very low ____ activity. The _____ of CDK inhibits the binding of these helicases to origins of replication.
ORCs
Licensing
CDK
Phosphorylation
Binding of helicases to origins of replication early in G1 results, in the formation of a ________ _____, which triggers DNA replication, and entrance into the S phase.
Pre-replicative complex (Pre-RC)
_____ ____ is synthesized and accumulates throughout S and G2. _____ ___ binds to CDK 1 and M- Cdk. M-Cdk is _____ at both activating and inhibiting sites by ____ and _____ kinases, respectively, resulting in very low activity. M-Cdk activation occurs through the activation of ____ _____, which removed the inhibitory phosphate. The phosphatase activity of Cdc25 is _____ by Phosphorylation of M-Cdk and the activity of the inhibitory Wee1 kinase is _____ by phosphorylation of M-Cdk. This comprises ____ ____ feedback loops, which lead to a switch like activation of M-Cdk, triggering the sudden onset of _____ phase.
Cyclin B
Cyclin B
Phosphorylated
CAK
Wee1
Cdc25 phosphatase
Enhanced
Inhibited
Double positive
M- phase
M-Cdk ____ APC/C which allows the binding of an activator protein _____. APC/C then targets securin, the destruction of securin liberates active _____ which initiates anaphase by destroying cohesins.
Phosphorylates
Cdc20
Separase
The three cell cycle checkpoints are ___, ___, and ___. Cell cycle progression is halted if things are not going well at these points.
G1/S
G2/M
M
Under healthy conditions, p53 upregulates ______, which is a ubiquitin ligase that targets p53 for destruction. This is a _____ feedback loop whereby p53 limits its own quantity.
Mdm2
Negative
p53 acts as a transcription factor turning on the expression of genes coding for _____, which arrests the cell cycle allowing time for the cell to repair damaged DNA.
CKIs
____ is the spindle assembly checkpoint
SAC
____ = the number of homologs represented, will normally be 2 in mitotic cells, 1 or 2 in meiotic cells
____ = total number of copies of a chromosome present
N
C
The two Mphase of meiosis are called _____ and _____.
Meiosis I and Meiosis II
____ ____ form between chromatids of different homologous on average at 2 to 3 locations per chromosome pair
Recombination nodules
_____ ______ is the random distribution of paternal and maternal homologs to the two daughter cells. Thus in meiosis, each daughter cell receives a different mix of replicated and recombinant homologs
Independent assortment
The protein _____ protects the centromeric cohesions from being digested by Separase during meiosis I. During metaphase II _____ is dislodged and Separase destroys ______ , allowing the separation of chromatids
Shugoshin
Shugoshin
Cohesions
Completion of meiosis II forms haploid ____ in males and ____ in females
Spermatids
Ovum
_____ is what we see. The ____ is the actual generic variants (alleles).
Phenotype
Genotype
