Chapter 12 - cell cycle

CHAPTER 12 CELL CYCLE 1 The The ability ability of of organisms organisms to to produce produce more more of of their their own own kind kind is is the the one one characteristic characteristic that that best best distinguishes distinguishes living living things things from from nonliving nonliving matter. matter. Cell Cell division division functions functions in in reproduction, reproduction, growth, growth, and and repair. repair. Cell Cell division division is is an an integral integral part part of of the the cell cell cycle, cycle, the the

life life of of aa cell cell from from its its origin origin in in the the division division of of aa parent parent cell cell until until its its own own division division into into two two daughter daughter cells. cells. Mitosis Mitosis results results in in GENETICALLY GENETICALLY IDENTICAL IDENTICAL daughter daughter cells! cells! Cell Division 2 Genome Genome Genome = =all allof ofaacells cellsgenetic genetic information information -- Prokaryotes Prokaryotes Genome Genomeisis usually usuallyaaSINGLE SINGLElong longDNA DNA molecule molecule -- Eukaryotes EukaryotesGenome Genomeisis usually usuallyseveral severaldifferent

differentDNA DNA molecules molecules During Duringinterphase interphase (most (mostof ofthe thecell cell cycle), cycle),the theDNA DNAisisin in the theform formof of chromatin chromatin..ItItthen then goes goesthrough throughaa series seriesof of changes(see changes(seepic) pic)to to form forminto into chromosomes. chromosomes. This This occurs occurswhen whenthe the cell cellisisabout aboutto to 3 enter mitosis and Chromatin Chromatin long, long, thin thin strands strands of of DNA; DNA; DNA DNA is is normally normally in in this

this form form unless unless itit is is getting getting ready ready to to divide divide The DNA molecule carries The DNA molecule carries several several hundred hundred to to aa few few thousand thousand genes. genes. The proteins maintain the The proteins maintain the structure structure of of the the chromosome chromosome and and help help control control the the activity activity of of the the genes genes Chromosomes Chromosomes coiled coiled up up DNA; DNA; DNA DNA takes takes this this form form when when itit is is about about to to go go through through cell cell division division Chromatin vs. Chromosomes 4

Chromosome Number Each Each specie specie has has aa characteristic characteristic number number of of chromosomes chromosomes in in their their body body cells cells In In human human somatic somatic cells cells (body (body cells cells NOT NOT egg/sperm), egg/sperm), there there are are 46 46 chromosomes chromosomes (23 (23 pairs) pairs) called called DIPLOID DIPLOID In In reproductive reproductive cells, cells, or or gametes gametes (egg/sperm), (egg/sperm), they they only only have have ONE ONE set set of of chromosomesso chromosomesso in in humans humans they they only only have have 23 23 chromosomes chromosomes called called HAPLOID HAPLOID The

The number number of of chromosomes chromosomes in in gametes gametes is is ALWAYS ALWAYS half half of of the the number number of of the the number number of of chromosomes chromosomes in in somatic somatic cells. cells. 5 Chromosomes As As aa cell cell gets gets ready ready to to divide, divide, the the chromatin chromatin coils coils up up into into chromosomes. chromosomes. Chromosomes Chromosomes are are composed composed of of two two sister sister chromatids. chromatids. They They are are connected connected along along their their length length by by proteins proteins called called cohesins, cohesins, forming forming an an attachment attachment known known as as sister

sister chromatid chromatid cohesion. cohesion. As As the the chromosomes chromosomes condense, condense, the the region region where where the the chromatids chromatids connect connect shrinks shrinks to to aa narrow narrow area, area, made made up up of of two two centromeres. centromeres. Keep Keep in in mind mind that that AS AS SOON SOON AS AS the the chromosome chromosome splits splits in in anaphase, anaphase, the the sister sister chromatids chromatids are are 6 now considered separate chromosomes. Cell Cycle Interphase Interphase Growth Growth portion portion of of the the cell cell cycle; cycle; includes includes G1, G1, S, S, G2; G2; DNA DNA is is copied copied here

here Mitosis Mitosis Division Division of of the the nucleus; nucleus; contains contains the the phases phases of of mitosis mitosis (PPMAT); (PPMAT); results results in in two two daughter daughter cells cells identical identical to to the the parent parent cell; cell; occurs occurs to to make make body body cells cells The The M M phase phase (mitosis (mitosis and and cytokinesis) cytokinesis) alternates alternates with with the the much much LONGER LONGER Interphase. Interphase. Meiosis Meiosis Makes Makes gametes gametes (egg/sperm (egg/sperm we we will will explore explore this this in in Chapter Chapter 13) 13)

Cytokinesis Cytokinesis Division Division of of cytoplasm; cytoplasm; follows follows mitosis mitosis and and meiosis; meiosis; 7 Interphase Interphase Interphase is is the the growth growth period period of of the the cell cell cycle. cycle. ItIt takes takes up up 90% 90% of of the the cells cells life. life. During During this this point point the the DNA DNA is is in in the the form form of of chromatin. chromatin. ItIt is is divided divided into into 33 sections: sections: G1, G1, S, S, G2. G2. G1 G1 (First (First Gap) Gap) grows grows and and copies copies organelles

organelles SS (Synthesis) (Synthesis) copies copies the the DNA DNA (chromosomes (chromosomes duplicated) duplicated) G2 G2 (Second (Second Gap) Gap) grows grows more more and and prepares prepares for for cell cell division division 8 Mitosis Cell Division Mitosis Mitosisisisthe the process processof ofcell cell division divisionin in eukaryotic eukaryoticcells. cells. ItIt consists consistsof ofseveral several phases: phases: Prophase Prophase Prometaphase Prometaphase Metaphase Metaphase Anaphase Anaphase Telophase Telophase PPMA PPMA TT 9 Late Interphase (not mitosis yet)

In In late late interphase, interphase, the the chromosomes chromosomes have have been been duplicated duplicated but but are are not not condensed. condensed. AA nuclear nuclear membrane membrane surrounds surrounds the the nucleus. nucleus. The The centrosome centrosome has has replicated replicated to to form form two two centrosomes. centrosomes. In In animal animal cells, cells, each each centrosome centrosome features features two two centrioles. centrioles. 10 Prophase Prophase Prophase -- Chromatin Chromatin is is now now coiled coiled into

chromosomes into chromosomes which which each each have have 22 sister sister chromatids chromatids --Nucleolus Nucleolus disappears disappears --Mitotic Mitotic spindle spindle (composed (composed of of centrosomes centrosomes and and microtubules) microtubules) forms forms (will (will eventually eventually pull pull apart apart the the chromatids chromatids and and lengthen lengthen cell) cell) -- Centrosomes Centrosomes move move away away from from each each other other 11 Prometapha se Prometaphase Prometaphase --Nuclear Nuclear envelope envelope breaks breaks down down -- Spindle Spindle can can interact interact with with the the chromosomes

chromosomes --Each Each of of the the two two chromatids chromatids of of aa chromosome chromosome has has aa kinetochore, kinetochore, aa specialized specialized protein protein structure structure located located at at the the centromere. centromere. Kinetochore Kinetochore microtubules microtubules attach attach to to the the kinetochore kinetochore of of the the chromosomes; chromosomes; eventually eventually they they will will pull pull the the sister sister chromatids chromatids apart apart to to separate separate Non-kinetochore Non-kinetochore microtubules microtubules these these do do not not attach attach to to the the chromosomes; chromosomes; instead, instead, their their function function is is to to elongate elongate the

the 12 Metaphase = Middle Kinetochore Kinetochore microtubules microtubules are are now now attached attached and and they they move move the the chromosomes chromosomes to to the the middle middle of of the the cell cell (METAPHASE (METAPHASE PLATE!). PLATE!). The The centrosomes centrosomes are are on on the the opposite opposite sides sides of of the the cell. cell. 13 Anaphase *** *** As As soon soon as as the the centromere centromere splits, splits, the the sister sister chromatids chromatids are are considered considered individual individual chromosomes*** chromosomes*** Anaphase Anaphase

--Centromere Centromere splits splits -- Sister Sister chromatids chromatids get get pulled pulled apart apart because because the the kinetochore kinetochore microtubules microtubules shorten shorten (motor (motor proteins) proteins) -- Poles Poles of of the the cell cell move move further further apart apart 14 To To pull pull the the chromosomes chromosomes (chromatids) (chromatids) apart, apart, the the microtubule microtubule starts starts to to break break down down at at the the kinetochore kinetochore end. end. The The motor motor proteins proteins (think (think cilia/ cilia/ flagella) flagella) walk walk down down the the microtubule microtubule to to move move the the chromosomes chromosomes closer closer

to to the the centrosome centrosome which which is is at at one one side side of of the the cell. cell. The The tubulin tubulin subunits subunits can can then then go go join join non-kinetochore non-kinetochore microtubules microtubules so so that that they they can can get get longer longer and and lengthen lengthen the the size size of of the the cell. cell. 15 Telophase Telophase Telophase --Daughter Daughter nuclei nuclei form form at at poles poles -- New New nuclear nuclear envelopes envelopes form form around around DNA DNA -- Chromosomes Chromosomes uncoil uncoil into into chromatin chromatin -- Cytokinesis

Cytokinesis starts starts --Nucleolus Nucleolus starts starts to to reform reform 16 Mitosis Division of Nucleus 17 Mitosis Division of Nucleus 18 Cytokinesis Division of Cytoplasm 19 Cleavage Cleavage Furrow Furrow Pinches Pinches an an animal animal cell cell in in two two Cytokinesis Cytokinesis in in animal animal cells; cells; actin actin filaments filaments form form aa ring ring near near the the metaphase metaphase plate; plate; myosin myosin filaments filaments interact interact with with the the actin actin and and contract contract the the ring. ring. 20 Cell

Cell Plate Plate In In plant plant cells, cells, aa cell cell plate plate forms forms after after telophase. telophase. Vesicles Vesicles from from the the golgi golgi form form near near the the old old metaphase metaphase plate. plate. They They are are moved moved there there by by microtubules. microtubules. Eventually Eventually the the vesicles vesicles fuse fuse to to form form the the cell cell plate. plate. This This develops develops into into the the cell cell wall. wall. 21 The The mitotic mitotic spindle

spindle distributes distributes chromosomes chromosomes to to daughter daughter cells. cells. The The mitotic mitotic spindle, spindle, fibers fibers composed composed of of microtubules microtubules and and associated associated proteins, proteins, is is aa major major driving driving force force in in mitosis. mitosis. Assembly Assembly of of the the spindle spindle microtubules microtubules starts starts in in the the centrosome. centrosome. In In animal animal cells, cells, the the centrosome centrosome has has aa pair pair of of centrioles centrioles at at the the center, center, but but the the centrioles centrioles are are not not essential essential for for cell

cell division. division. The The centrosomes centrosomes of of most most plants plants lack lack centrioles, centrioles, but but still still form form mitotic mitotic spindles. spindles. Mitotic Spindle 22 Binary Binary Fission Fission Prokaryotic Prokaryotic cell celldivision; division; single single bacterial bacterial chromosome chromosome is is replicated replicated starting starting at at the the origin origin of of replication; replication; while while the the chromosome chromosome is is replicating, replicating, the the cell cell elongates; elongates; no no mitotic mitotic spindle spindle is is used; used; produces produces two two 23 identical identical daughter

daughter cells cells Link Between Binary Fission and Mitosis Dinoflagellates Dinoflagellates = = spindle spindle goes goes THROUGH THROUGH the the nuclear nuclear membrane membrane Diatoms Diatoms = = spindle spindle forms forms WITHIN WITHIN the the nuclear nuclear envelope envelope 24 Frequency of Cell Division The The frequency frequency of of cell cell division division varies varies with with cell cell type. type. Some Some human human cells cells divide divide frequently frequently throughout throughout life life (skin (skin cells). cells). Others Others human human cells cells have have the

the ability ability to to divide divide but but keep keep itit in in reserve reserve (liver (liver cells). cells). Mature Mature nerve nerve and and muscle muscle cells cells do do not not appear appear to to divide divide at at all all after after maturity. maturity. 25 Chemicals Chemicals in in the the cytoplasm cytoplasm can can trigger trigger cell cell division division see see picture picture above. above. Frequency Frequency and and speed speed of of cell cell division division varies varies depending depending on on the the type type of of cell. cell. There There are are checkpoints checkpoints along along the the way

way that that the the cell cell needs needs to to pass pass in in order order to to complete complete cell cell division. division. Checkpoints in the Cell Cycle 33Major Major Checkpoints: Checkpoints: G1 G1 G2 G2 M 26 M IfIf itit leaves leaves the the cell cell cycle, cycle, itit enters enters GG00 phase; phase; this this is is aa non-dividing non-dividing state; state; most most of of our our human human cells cells are are in in the the GG00 phase; phase; HOWEVERsome HOWEVERsome cells cells can can be be called called back back to to the the cell cell cycle cycle by

by external external cues cues like like growth growth factors factors during during an an injury; injury; highly highly specialized specialized nerve nerve and and muscle muscle cells cells hardly hardly ever ever divide divide G1 Checkpoint This This is is the the gogoahead ahead checkpoint; checkpoint; ifif itit passes passes this this checkpoint, checkpoint, itit usually usually proceeds proceeds all all the the way way through through mitosis mitosis = = most most important important checkpoint! checkpoint! This This checkpoint checkpoint is is regulated regulated by by several several different different cyclin cyclin dependent dependent kinases kinases (see

(see next next slide!) slide!) 27 Cyclins/ Kinases/ cdks Protein Protein Kinase Kinase = = ALWAYS ALWAYS PRESENT PRESENT in in cell, cell, but but needs needs to to be be attached attached to to cyclin cyclin to to be be active active Cyclin Cyclin = = levels levels of of this this protein protein FLUCTUATE FLUCTUATE with with the the cell cell cycle cycle (high (high in in interphase, interphase, low low in in mitosis); mitosis); Cdk Cdk = = cyclin cyclin dependent dependent kinase kinase The The G1 G1 checkpoint checkpoint is is regulated regulated by by 33 cdks cdks 28 G2 Checkpoint Regulated Regulated by

by the the cdk cdk MPF MPF MPF MPF = = Maturation Maturation Promoting Promoting Factor Factor or or M M Phase Phase Promoting Promoting Factor Factor MPF MPF is is aa cyclin cyclin dependent dependent kinase kinase (NEEDS (NEEDS cyclin) cyclin) ItIt initiates initiates mitosis mitosis by by breaking breaking down down the the cyclin cyclin that that itit is is associated associated with; with; once once the the cyclin cyclin is is broken broken down, down, itit is is switched switched off off and and becomes becomes inactive inactive until until itit gets gets new new cyclin cyclin (towards (towards the the end end of of interphase) interphase) Remember:

Remember: Cyclin Cyclin levels levels rise rise sharply during S and G phases,29 M Checkpoint This This checkpoint checkpoint occurs occurs in in metaphase metaphase and and ensures ensures that that all all of of the the chromosomes chromosomes are are properly properly attached attached to to the the spindle spindle at at the the metaphase metaphase plate plate before before anaphase anaphase begins. begins. IfIf they they are are NOT NOT properly properly attached, attached, the the kinetochores kinetochores give give the the delay delay signal signal and and this this keeps keeps APC APC (anaphase (anaphase promoting promoting factor) factor) inactive. inactive. This This helps helps to to ensure

ensure the the that that daughter daughter cells cells do do not not end end up up with with aa missing missing or or extra extra chromosome. chromosome. Note: Note: the the APC APC is is NOT NOT aa cdk, cdk, but but aa complex complex of of several several other other proteins proteins Once Once they they are are attached attached and and APC APC activates, activates, itit gives gives the the signal signal for for the the proteins proteins holding holding the the sister sister 30 chromatids chromatids together together to to break break down down Growth Factors Growth Growth Factors Factors are are proteins proteins that that are

are released released by by one one group group of of cells cells that that cause cause others others to to divide. divide. Different Different types types of of cells cells respond respond different different to to individual individual and and various various combinations combinations of of growth growth factors. factors. Ex. Ex. PDGF PDGF (Platelet (Platelet Derived Derived Growth Growth Factors) Factors) = = produced produced by by blood blood platelets; platelets; platelets platelets release release itit at at the the site site of of injury; injury; causes causes cell cell division; division; some some cells cells will will only only divide divide ifif PDGF PDGF is is there there Growth Growth factors

factors play play aa role role in in Density Density dependent dependent inhibition inhibition and and anchorage anchorage dependence. dependence. 31 Density Density Dependent Dependent Inhibition Inhibition = = cells cells will will form form aa single single layer layer and and stop stop dividing; dividing; ifif aa gap gap is is created, created, they they will will divide divide to to fill fill the the gap gap and and then then stop stop again; again; cancer cancer cells cells keep keep dividing dividing and and create create huge huge masses masses of of cells cells (tumors); (tumors); as as cells cells divide divide and and become

become more more and and more, more, the the amount amount of of growth growth factors/nutrients factors/nutrients become become insufficient, insufficient, so so they they have have to to stop stop dividing dividing Anchorage Anchorage Inhibition Inhibition = = in in order order to to divide, divide, cells cells must must be be anchored anchored to to something something (usually (usually the the ECM ECM of of other other cells) cells) 32 HeLa HeLa Cells Cells = = these these are are cancer cancer cells cells taken taken from from aa cervical cervical tumor tumor in

in Henrietta Henrietta Lacks Lacks in in 1951; 1951; they they are are still still dividing dividing which which hints hints to to scientists scientists that that some some cancer cancer cells cells may may be be immortal. immortal. Cancer Cancer cells cells are are not not under under the the normal normal controls controls of of the the cell. cell. They They divide divide constantly; constantly; and and ifif they they ever ever stop stop its its at at random random points. points. They They do do not not exhibit exhibit density density dependent dependent inhibition inhibition (instead (instead they they pile pile up up and

and form form tumors) tumors) or or anchorage anchorage inhibition. inhibition. They They may may not not require require growth growth factors factors to to divide, divide, OR OR Cancer Cells Henrietta Lacks 33 Transformation Transformation = = process process that that converts converts normal normal cells cells to to cancer cancer cells; cells; NORMALLY NORMALLY the the immune immune system system recognizes recognizes and and destroys destroys transformed transformed cells cells Benign Benign Tumor Tumor = = tumor tumor that that remains remains at at the the original original site; site; can can be be removed removed by by surgery surgery Malignant Malignant Tumors

Tumors = = leaves leaves the the original original site site and and spreads spreads to to other other organs organs thereby thereby impairing impairing their their functions; functions; carried carried by by blood blood and and lymph lymph (spreading (spreading process process is is called called metastasis) metastasis) Angiogenesis Angiogenesis = = recruitment recruitment of of blood blood vessels vessels to to new new tumors tumors so so 34

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