CELL BIO: CH. 18: CELL-DIVISION CYCLE

all cells are created by what cycle

cell cycle

during mitosis, are our chromosomes condensed or loose

condensed

what shape are our chromosomes in during mitosis

X-shape

do we express our genes during mitosis

no

what are the three phases of interphase

G1, S, G2

what molecule complex drives the cell cycle forward

cyclin-CDK

cyclin-CDK is what type of regulation

quartneray (them binding means they agree to push cells to divide as they are independently regulated)

cells have what to make sure that the cells is on the right track to divide

check points

G0 phase

cells that are not currently dividing but are still doing their function

what happens in S-phase

DNA replication

Where does DNA replication begin?

origin of replication

how is S-phase initiated

Cyclin-CDK complex must bind to Ori and lets Helicase bind and become activated

after we replicate DNA and go from linear chromosomes to X-shaped chromosomes, do we have the same number of chromosomes or not and how much DNA do we have

same number of chromosomes, double DNA

after the X-shape is made, what is added to the sister chromatins to hold them together

cohesion rings

mitosis is started by what complex

cyclin-CDK

once a cyclin-CDK is turned on to start mitosis, what feedback loop happens and what does it do

positive; turns on more M-Cdk

why is there positive feedback to turn on more M-Cdk

DNA is vulnerable in mitosis as genes aren't being expressed so we need to go through mitosis really fast

what do condensin rings do

take unwound DNA and condense them into the X-shaped chromosomes

what complex turns on the condensin rings

M-Cdk

in prophase, does the nucleus exist

yes

how many centrosomes are in prophase

2 (normal cells have 1)

in pro metaphase, what organelle disappears that allows for the cytoskeletons to attach to the chromosomes

nucleus (nuclear envelope)

where do cytoskeletons bind to on the chromosomes

centromere

what are the phases of mitosis

prophase, prometaphase, metaphase, anaphase, telophase

what are the parts of M-phase

mitosis and cytokinesis

What happens in metaphase?

Chromosomes line up in the middle of the cell

what allows for the chromosomes line up in the middle of the cell during metaphase

sister chromatids are attached, so the opposite ends of the microtubules pulling will cause them to be in the center

what happens in anaphase

Sister chromatids split and move to either pole (Disjunction)

in anaphase, how many chromosomes are there relative to the beginning

double the number of chromosomes

where are the chromosomes pulled towards in anaphase

opposite centrosomes

telophase is when what organelle starts to reform

nuclear envelope

why would the nuclear envelope start to reform during telophase even though the two cells haven't even finished dividing

DNA is the formula for life so must protect it as soon as possible

what disease is the result due to damage to the DNA because the nuclear envelope isn't functioning

progeria

does the formation of the nuclear envelope occur before or after the creation of two new daughter cells

before

cytokinesis

Division of the cytoplasm during cell division; two daughter cells

in M-phase for animal cells, what are the two cytoskeletal structures that help it

microtubules, actin and myosin

microtubules play a major role in what phase of M-phase

mitosis (forms the mitotic spindle)

actin and myosin play a major role in what phase of M-phase

cytokinesis (forms contractile rings)

contractile rings

provide mechanical force to cleave cells during cytokinesis

microtubules come out of what organelle

centrosome

do centrosomes divide

yes

G1 phase

cells doing their jobs, open and loose DNA

S phase

DNA and centrosome replication

do microtubules grow independently or conjointly

independently

do microtubules have a polarity

yes

interpolar microtubules

microtubules that associate with microtubules from other centrosome

what is the point of inter polar microtubules

forms mitotic spindle and helps stabilize cell

what are the three types of mitotic microtubules

aster, kinetochore, interpolar

kinectochore microtubules

Attach to the kinectochore protein on the centromere of each chromosome

what is the function of kinectochore

move chromosomes

function of interpolar microtubules

stabilize and create mitotic spindle; structure between two centrosomes

aster microtubules

connect spindle poles to cell membrane

function of aster microtubules

stabilize the cell (when the kinectochore microtubules grab chromosomes and pull, need aster to anchor to other parts of cell to keep cell shape during this process)

what must be broken to separate the sister chromatids to go from metaphase to anaphase

cohesion rings

what enzyme cleaves cohesion rings

separase

normally, is separate on of off

off

what protein inhibits separase at rest

securin

the complex of securin inhibiting separase is an example of what type of regulation

quartenary

what signaling protein is needed to let the cell know to move from metaphase to anaphase

APC (anaphase promoting complex)

how does the active APC actually remove securin

add ubiquitin groups to securin which allows proteosomes to know that they must degrade

how do we break apart the nuclear envelope

phosphorylating pieces of the nuclear envelope

since we want to prevent damage to the DNA and genome and want to protect it as soon as well can, in what phase does the nuclear lamina start to reappear

telophase

how is the nuclear lamina rebuilt

dephosphorylating the nuclear lamina pieces and putting them together

when does the contractile ring form

telophase (after nuclear lamina reforms)

what does the contractile ring do

split the cell into two (telophase to cytokineses is)

instead of myosin and actin contractile rings, how do plant cells divide into two daughter cells

put up a new cell wall in-between sister cells

can a cell function with only DNA

no (must have all organelles too)

while cells are being made, what else is happening to balance the amount of cells in the body

apoptosis

apoptosis

programmed cell death (suicide)

what are the 3 reasons why a cell would do apoptosis

create structures, get rid of structures we dont need anymore, control organ size

how is apoptosis is used to create structures

we are all born with flippers as hands, so we need apoptosis to kill the cells in-between our fingers

how is apoptosis used to get rid of structures not needed

for frogs and tadpoles, as soon as it becomes a frog, it doesn't need a tail because it doesn't need to swim

can organ sizes change

yes

when we are pregnant what happens to our organs

makes it smaller

if we expose human liver to drugs that stimulate liver cell division (phenobarbital), what will happen to the liver size

enlarge

how do livers return to normal size after the removal of a drug

apoptosis

necrosis

sudden, unexpected death of tissue

Are necrosis and apoptosis the same?

no

if one cell bleeds out, what happens to the neighboring cells

also die because of polarity changes

Apoptosis

programmed cell death, safe and normal (no effect on surrounding cells

Caspases

family of proteases that cut up proteins and DNA during apoptosis

caspase cascade

one "initiator" caspase cleaves and activates many other caspases (one cascade can only break down some cells and activate some cascade)

is the process of cascapse cascade irreverisible

yes (once it starts, cant stop and cell will be taken apart)

what family of proteins regulates apoptosis

Bcl-2

what are the two types of Bcl-2 proteins

proapoptotic, antiapoptotic

does proapoptotic increase or decrease apoptosis

increase

does antiapoptotic increase or decrease apoptosis

decrease

what are the examples of genes that are antiapoptotic

Bcl-2, Bcl-XL

what are the examples of genes that are proapoptotic

Bax, Bak

how do anti-aproptic proteins block apoptosis

block caspase activation

how do anti-aproptic proteins block cascade activation

blocking release of cytochrome C

how are Bcl-2 pro-apoptic proteins activated

activated by death signals which is the release of cytochrome C from mitochondria which starts formation of apoptosome which turns on first caspace

what types of factors suppress apoptosis

survival factors

what is the name of the signaling molecules that stimulate cell division

mitogens

what factors stimulate cell growth (inc. in size and mass by promoting gene expression and suppressing protein degradation

growth factors

true or false: many signaling molecules often stimulate more than one

true

when we are first developing, are neurons rapidly dividing

yes, right before birth, a bunch of neurons died because limited amount of survival factors can only have a certain number of cells alive

true or false: every cell must have a neuron

true

during development, why are we overproducing neurons

we must make sure that every cell receives a neuron so that it is viable

what is the mechanism by which survival factors from other cells can block apoptosis

survival factor from sending cell binds to receptor which activates signaling cascades which activates TF which creates Bcl-2 gene, making Bcl-2 protein, blocking apoptosis