Cell Cycle Control & Cell Division Part II (Exam IV) Flashcards by Annabella Moody

Q

Passage through the start checkpoint in late G1 launches DNA replication & the ______ of the cell cycle

A

S-Phase

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Q

DNA replication occurs at specific sites:

A

Origins of replication

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Q

The initiation phase of DNA replication is divided into two steps:

A

1- late mitosis-early G1
2- Onset of S phase

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Q

In the first initiation step of DNA replication in late mitosis-early G1 ______ assembles at the origins of replication

A

Prereplication complex

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Q

In the second step of initiation of DNA replication, in the onset of S phase is when the prereplication complex _____ the formation of the _____

A

Nucleates
Preinitiation complex

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Q

The prereplication complex is formed by various molecules including:

A

Cdc6 & Cdt1 & also a helicase

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Q

The prereplication complex occurs in:

A

G1

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Q

The prereplication complex forms at the:

A

Origins of replication

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Q

After the prereplication complex is formed, it is just waiting on:

A

The right signals

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Q

The signal that the phosphorylation complex is waiting on is:

A

S-Cyclin-Cdk

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Q

The S-cyclin-Cdk is present in the S phase of the cell cycle because of:

A

The G1/S-Cdk activity that precedes it

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Q

The S-Cyclin will function to phosphorylate the _____ thereby degrading it

A

Cdc6

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Q

After the S-cyclin has degraded the Cdc6, another set of proteins come in called the:

A

Preinitiation complex

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Q

The Preinitiation complex functions to:

A

Launch DNA replication

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Q

At the end of DNA replication is when the ______ phase starts

A

G2/M

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Q

The three steps of G1, S & G2/M:

Starts with the _______
Add _____, _____ & ______ to form the prereplication complex
The prereplication complex is converted into a _____ by addition of proteins that bind to the DNA through the action of ______ phosphorylating other proteins present & the DNA is opened in up by the action of _____

Once DNA replication is complete, you enter the ______ checkpoint

A

1- origin of replication
2- Cdc6, Cdt1, helicase
3- preinitiation complex, S-Cdk, helicase

G2/M

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Q

What cell cycle phase does this process occur in:

Formation of the prereplicative complexes at all the replication origins

A

G1

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Q

What cell cycle phase does this process occur in:

Starts by the formation of the preinitiation complex & initiation driven by the S-Cdk

A

S

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Q

What cell cycle phase does this process occur in:

DNA replication occurs

A

S

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Q

What cell cycle phase does this process occur in:

M-Cdk comes along & that triggers chromosome separation & cytokinesis to create the daughter cells

A

M

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Q

What cell cycle phase does this process occur in:

Driven by the activation of APC/C complex that leads to inactivation of the Cdk

A

G1

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Q

What cell cycle phase does this process occur in:

Assembly of the prereplicative complexes at the origins of replication

A

G1

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Q

If we are talking about the G2/M checkpoint, which phase of cell-cycle is this associated with:

A

Mitosis

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Q

The G2/M checkpoint is responsible for insuring that:

A

All of the DNA has been properly replicated

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What molecules activity abruptly increases at the G2/M checkpoint

M-Cdk

Abrupt increases of the M-Cdk activity at the G2-M checkpoint drives:

Entry into mitosis & early mitosis events

Responsible for inducing the assembly of the mitotic spindle, chromosome condensation, promotes breakdown of nuclear envelope, rearrangement of the actin cytoskeleton & Golgi apparatus:

M-Cdk mediated phosphorylation of specific proteins

Events triggered by M-Cdk mediated phosphorylation of specific proteins in conjunction with two other families of protein kinases (4):

1- induces assembly of mitotic spindle 2- chromosome condensation 3- promotes breakdown of nuclear envelope 4- rearrangements of the actin cytoskeleton & Golgi apparatus

How long does it take mitosis from start to finish:

1 hour

Five phases of mitosis:

Prophase Prometaphase Metaphase Anaphase Telophase

The interphase events of mitosis encompass:

G1/G0 phase S phase G2 phase

What phase is separate from interphase:

M phase

At prophase the replicated chromosomes consist of:

Two closely-associated sister chromatids

What phase of mitosis is this: Intact nuclear envelope Centrosomes forming outside the nucleus- beginning to move apart Forming mitotic spindle Condensing replicated chromosomes consisting of two sister chromatids

Prophase

Allows for the chromosomes to attach to spindle microtubules via their kinetochores:

Breakdown of nuclear envelope

What phase of mitosis is this: Breakdown of nuclear envelope Chromosomes attach to spindle microtubules via their kinetochore Chromosomes in active motion

Prometaphase

Important for the moving apart of chromosomes:

Kinetochores

What phase of mitosis is this: Chromosomes are aligned at the equator of the spindle Kinetochore microtubules attach sister chromatids to opposite poles of the spindle

Metaphase

What phase of mitosis is this: Sister chromatids synchronously separate to form two daughter chromosomes Kinetochore microtubules shorten Spindle poles move apart

Anaphase

What phase of mitosis is this: Set of daughter chromosomes at the spindle pole Set of daughter chromosomes decondense New nuclear envelope reassembles around each set Contractile ring starts to form

Telophase

What marks the end of mitosis:

Completing the formation of of two nuclei

During telophase, the division of the cytoplasm begins with:

Contraction of the contractile ring

Cytoplasm is divided in two by a contractile ring of actin & myosin filaments, which pinches the cell in two to create two daughters, each with one nucleus:

Cytokinesis

Separation of the two daughter cells is accomplished through:

Cytokinesis

Following cytokinesis each daughter cell will have a complete ______ surrounding all of the ____

Nuclear envelope; chromosomes

Following cytokinesis we have:

Two identical daughter cells

When fewer ribosomes are made (for example in an ESCO2 mutation) this will ultimately lead to:

Decreased protein synthesis

Prenatal growth retardation (mild to severe), craniofacial abnormalities such as microcephalic & cleft lip/palate & limb malformations due to a homozygous mutation in ESCO2:

Roberts syndrome

Roberts syndrome is due to a ______ mutation in the gene _____

Homozygous mutation; ESCO2

ESCO2 is a gene responsible for encoding a _____ important for the formation of the cohesion complex that binds to chromosomes & creates cohesion between sister chromatids

Acetyltransferase

The Acetyltransferase encoded by ESCO2 is important in the formation of the:

Cohesion complex

The cohesion complex is responsible for binding chromosomes & creating:

Cohesion between sister chromatids

Studies suggest that the ESCO2 mutation lead to decreased:

Ribosome production

The metaphase to anaphase transition involves:

Proteolysis

During proteolysis: The APC/C protein binds to ____ to produce an active APC/C molecule This process is regulated by: The active M-Cdk complex ubiquitylates & degrades a protein called: Securin is normally bound to an inactive protein called: When securin is ubiquinated & subsequently degrades the separase becomes _____

Cdc20 M-Cdk Securin Separase Active

Molecule responsible for breaking down the cohesion complexes that hold the sister chromatids together:

Activated separase

The breakdown of the cohesion complexes by activated separase occurs during:

Anaphase

Three types of basic signals that control cell division:

Mitogens, growth factors, survival factors

Stimulate cell division mainly by stimulating G1/S-Cdk activity that inhibits intracellular negative controls that block the progression through the cell-cycle

Mitogens

Stimulate cell growth (increase cell mass) by stimulating protein synthesis & inhibiting protein degradation:

Growth factors

Suppress programmed cell death (apoptosis)

Survival factors

Mitogens generally act through a highly generalized:

Cascade of mitogen-activated protein kinases (MAPK)

In the MAPK cascade: The initiate stimulus stimulates a ______

MAPKKK

In the MAPK cascade: The stimulation of the MAPKKK will lead to the simulation of _____ which leads to the stimulation of _______ & ultimately leading to ____

Stimulus —> MAPKKK —> MAPKK —> MAPK —> biological response

When mitogens bind to their cell surface receptor they will trigger:

Multiple intracellular signaling pathways

A major pathway that the mitogen trigger is the:

Small GTPase Ras signaling proteins

The Ras protein leads to the activation of a:

MAP-Kinase cascade

When the Ras leads to the activation of a MAP-kinase cascade that leads to the activation of:

Multiple early gene expression

Genes that are turned on very early or almost immediately after a mitogen binds to its receptor

Immediate early gene expression

One of the immediate early gene expressions is in a gene called:

Myc

Myc is thought to promote cell cycle entry by:

Increasing the expression of genes encoding the G1 cyclins

Results in increased G1-Cdk activity:

Myc increasing the expression of genes encoding G1 cyclins

One of the key functions of G1-Cdk is to activate the:

E2F proteins

The E2F proteins are:

Gene regulatory factors

Normally the E2F proteins are inhibited by an interaction between E2F & the:

Retinoblastoma protein family (Rb)

What is responsible for phosphorylating the Rb protein:

G1-Cdk

When the Rb protein is phosphorylated y G1-Cdk, this (3):

1- renders it inactive 2- reduces it binding to EF2 3- Frees EF2 to activate expression of its target genes

When the EF2 is free it:

Activates the expression of target genes

One of the immediate downstream targets of activated E2F is:

S-cyclin

When activated the E2F proteins leads to:

S-phase of gene transcription

Can directly lead to cell growth:

Growth factor & extracellular factor

Can directly lead to to cell division:

Mitogens & extracellular factor

Causes cell growth to go into cell division:

Extracellular factor

Summary of mitogen induced cell-cycle entry & S-phase initiation: 1- mitogen binds to its receptor leading to the activation of ____ 2- the activation of RAS leads to the activation of ____ 3- the activation of MAPK leads to a _____ 4- the transcription factor binds to ______ 5- the immediate early genes leads to _______ 6- myc expression leads to the activation of _____ 7- eventually you get DNA synthesis through early inhibition of ____

1- RAS 2- MAPK 3- transcription factor 4- immediate early genes 5- Myc expression 6- G1-Cdk 7- Rb protein

Signals through PI3 kinase/AKT signaling

EGF

EGF works through what three pathways:

1- ERK 2- JAK/STAT 3- PI3 Kinase/AKT

EGF pathway that leads to increased protein synthesis:

PI3/AKT

EGF pathway that leads to cell survival & protein synthesis:

ERK

EGF pathway that leads to cell survival:

JAK/STAT

Growth factor that has an affect on cell cycle progression

TGF-Beta

When TGF-beta binds to the type I & type II receptor complex, that leads to the:

SMAD pathway

Proteins targeted by the SMAD pathway

P15 P21

P15 & P21 proteins (that are targeted by SMAD) result in the inhibition of:

Cyclin E Cyclin D

Occuring at the same time of SMAD activating P21 & P15, there is a second pathway that leads to the inhibition of:

Cdc25

Growth factors are ultimately shutting down the cell cycle process in favor of:

Growth

When growth factors bind to their receptors this leads to:

A series of intracellular events

The signaling events resulting from growth factors binding to their receptors in many instances involve the:

PI3 kinase

The PI3 kinase leads to the intracellular signaling molecule:

PIP3

Downstream, PIP3 leads to the activation of the:

TOR pathway

The TOR pathway eventually leads to:

Protein synthesis & growth