The Cell Cycle and Cellular Reproduction

THE CELL CYCLE AND CELLULAR REPRODUCTION THE CELL CYCLE AND CELLULAR REPRODUCTION cell time its when cell stages resulting daughter going is cycle between the time cell a divides and the , and amount of DNA doubles organelles number of : phases (includes mitosis and stage happen grows bigger interphase (includes number of ↳ mitotic that alls divide to divide-o phases of the cell two ↳ ordered set of cycle- cytokinesis) INTERPHASE makes up ↳ amount cycle consists of cell most of in of 3 for cell time few a cycle hours stages : , to spend in interphase varies to En n Cyc . is committed to divide when growth signals are e . . embryonic g cells complete full cycle) G . , S , G2 stage ⑳ present - and nutrients are available . · ccur Stage before stage - will occur Otherwise , the cell , for adult mammal cells interphase takes about 20 hours (90 % of cell - Gy checkpoint performs usual function is the time when cell in if the DNA is DNA replication after DNA replication G cell recovers from G - > - G2 previous division , damaged and F cannot be repaired grows . M checkpoint. Mitosis Synthesis will not continue if e chromosomesarSeed . exit ↳ in (e . g . nerve and doubles organelles and muscle (also just functions of cells) do not complete cell cycle carries out normal daily cell) - are permanently arrested, interphase and enter phase called Go Go they perform normal signals without proper S , accumulates materials used for DNA checkpointbly some cells in size function but from other cells do not prepare (tightly controls for all division completion of cell - cannot leave Go cycle stage starts when each DNA chromosome replication occurs made up of one DNA double helix -o each double helix identical double helix molecule ↳ sister chromatids stay attached until separated = - after replication each is made chromatid , two identical chromatids during mitosis up of two = Sister chromatids Gz Stage from completion of division , e . DNA g. proteins M(mitotic) stage replication to onset of mitosis that form microtubules (form -> cell mitotic synthesizes spindle proteins that help in cell in mitotic stage and stage cytokinesis (division of cytoplasm mitotic spindle distributes daughter chromosomes to daughter nuclei during mitosis ↳ When Cytoplasm is divided daughter cells are formed of division includes mitosis (nuclear - division) ↳ , control of the cell signaling finish cycle proteins cell cycle are membrane received at plasma if stimulated by to growth factors (even cells in Go will them) cycle can either stop or continue at "checkpoints" (G G2 M) family of internal signaling proteins that increase and decrease as continues cyclins specific Cycling have to be present for cell to proceed from G stage to M and from G2 Stage stage cell , , cell cycle to S stage blebs ·D fragments. . collapses checkpoint of cell primary ↳ in ↳ mammal p = protein ↳ RB signaling = , first try called = to initiate RB G , checkpoint protein p53 stops protein 53= molecular ↳ Will ↳ cells cycle weight DNA interprets in Cycle G. when DNA is damaged kilodaltons repair but if levels of p53 rise , growth signals and nutrient retinoblastoma (cancer of the retina that mutation) at occurs apoptosis can be initiated availability signals when RB gene undergoes cell cycle can initiation if of M is DNA all stage damaged mitotic spindle apoptosis ↳ cell ↳ ↳ . are increases and THE 5 are not attached to cell death membrane cells) develops blisters white blood cells and /or engulfed by can keep - apoptosis cells neighboring apoptosis (caspases) are always present in all are usually internal or external activated signals by be number of decreases single - of histones human play some : body , and cells at number maintain homeostasis appropriate level (cell division of somatic cells look like string is ↳ to so string compacted RNA synthesis , (composed of more than most have structural role - histones - all packed into nucleus with 6 m that it can fit intervals around core of histones (2xHIA , HIB , H3 , H4) of beads (each bead called nucleosome by folding into zigzag structure back and forth into radial of enchromatin promote DNA molecule least 2m of DNA at loosely coiled euchromatin are being transcribed ↳ DNA or helix , is wound at fiber then loops DNA , cell contains ↳ double helix role in single H1 H2A , HIB , H3 H4 ↳ histones pack DNA > - contains a chromosome protein types ↳ chromosomes EUKARYOTIC CHROMOSOME eukaryotic 50 % checkpoint prevents be repaired here stops if neighboring help keep balance in cell division g. plasma , inhibitors but by events opposing ↳ e fragments that initiate held back programmed as up Closes contact to fragments enzymes cycle - > - properly rounds cell stage replicating stage S also has another chance to it often defined nucleus finished has not DNA completion of before at mitotic checkpoint another , if at G2 stop can transcription) - histone He controls represents active chromatin be accessed by coiling , loops RNA containing genes polymerase ( + that other factors needed form of chromosome have both most cells ↳ within nucleus microscope dark-stained fibers under = be seen can forms (depending which portions of inactive chromatin (contained on compacted more chromosomes are used more genes protein scaffold helps to condense chromosome cell division -o heterochromatin heterochromatin considered before of all of metaphase chromosomes - more compact not into often often transcribed form that is characteristic chromosomes are easier to more around than extended chromatin MITOSIS AND CYTOKINESIS eukaryotes cell division includes mitosis ↳ cytokinesis-division of cytoplasm in ↳ mitosis cytokinesis and distributed to two Clooks are ↳ like tangled mass of thin before mitosis chromatin each identifiable (can be easily species has characteristic full number of half the ↳s gametes of animals - are euchromatin highly - individual chromosomes coiled and condensed photographed and counted chromosome number chromosomes in number-haploid as threads becomes of each kind , most somatic cells ↳ cells in , ↳ daughter eukaryotic chromosomes associated with various proteins its when not undergoing cell division DNA and proteins are structured DNA ↳ separated sister chromatids are = and cell-diploid (2n) are > - includes two chromosomes diploid contains haploid number one chromosome of each kind cells - > replicate chromosomes duplicate most cell has to prepare for division , centrosome - chromosome that are organizes spindle apparatus important for duplication also In , : during mitosis zn chromosome nucleus divides - organelles (including movement) produces daughter nuclei S in ↳ of interphase chromosome stage now each chromosome has two identical double helical molecules ↳ each double helix is a chromatid ↳ sister chromatids ↳ ↳ , both together produces sister chromatids are constricted and attached to each other at centromere kinetochores nuclear division sister chromatids chromosome one are side of centromere at either during parent cell is duplicated in daughter two develop separate cll during division at centromere - each chromosomes , each daughter duplicated chromosome only having double helix molecule daughter one chromosomes distributed to equally daughter cells beach daughter gets from parent copy devision of the centrosome Centrosome is the main : microtubule-organizing center of the cell , also divides before start of mitosis ↳ in animal cells each centrosome contains barrel-shaped plant cells ↳ organize mitotic which contains microtubules ↳ assemble when tubulin subunits microtubulus formation PHASES can spindle ↳ or hollow cylinders disassemble when allows OF are cell to change join , as (not found made up of bundle of in microtubules up of tubulin when subunits disassemble spindle fibers shape fibers (each many made organelles-centrioles begin needed for to form - they become free again provides tubulin for spindle fiber all division MITOSIS be divided into 5 phases : Prophase nuclear division ↳ DNA is about to replication occured composed of happen during chromatin has condensed , chromosomes a parental interphase two sister chromatids held nucleus disappears spindle assembles as the two centrosomes , nuclear envelop ↳ centrioles have during no later stages particular plasma from duplicated and membrane each other , from of cell division orientation (no already visible centromere fragments migrate away in animal cells , microtubules radiate toward Ibrace centrioles together at chromosomes are are spindle formed yet the centrosomes -> called asters Prophase) Prometaphase (late separation sister chromatid Kinetochores appear on is prepared being side of centromere each to attach sister chromatids to kinetochore spindle Fibers ↳ fibers extend from poles kinetochore fibers toward pole one (will to chromosomes attach sister chromatids to , located at spindle be opposite poles of spindle toward other then and then soon - center chromosomes first pulled align Metaphase centromeres of chromosomes through metaphase plate passes unattached spindle fibers ( checkpoint properly alighed to single at cell center plane - chromosomes look like line across middle of the all straight M are to delays cell perpendicularly polar spindle fibers) reach = (invisible) beyond - indicates axis metaphase plate of anaphase until kinetochores of each chromosome start spindle fibers and of each chromosomes are aligned along and are of all division overlap attached metaphase plate Anaphase two sister chromatids two daughter daughter > - as are as daughters fibers kinetochore more sliding are toward past microtubule-associated > - anaphase chromosome are separated at centromere - produce chromosomes chromosomes with pulled duplicated antromere and single chromatid more toward opposite poles spindle fibers disassemble spindle poles poles themselves , more further apart to polar spindle each other proteins (e g. is shortest . motor molecules kinesin and of all phases dynein) involved in sliding process Telophase spindle same disappears number remnants of , new nuclear chromosomes as envelopes form around original of polar spindle fibers still chromosomes become more daughter chromosomes (each contains parent all > visible between nuclei diffused chromatin again , nucleolus forms in each daughter nucleus CYTOKINESIS when mitosis happens without interphase - > each all new in animal in gets share of cell structure > - it results in multinucleated cell telophase in , of difference because ↳ anaphase continues in Cytokinesis begins cytokinesis organelles but not that have been cytokinesis is different , new of cells have received share daughter organelles of plant cells forms nuclei start previously duplicated in animal and cells indentation of membrane between two at that time completed until clearage furrow clearage furrow deepens when band of actin filaments ( contractile ring) forms circular constriction between daughter cells ↳ contractile during telophase narrow bridge between two cells can be ring keeps until there is two independent cells separating Cytoplasm daughter a = seen in plant alls daughter flattened ↳ Golgi > - rigid cell wall prevents furrowing instead new cell walls built between are cells disc appears between apparatus produces daughter plant vesicles that fuse and form cell plate ( membrane releases molecules that strengthend by space between cellulose added daughter cells cells (near where more along metaphase plate microtubules to disc formed plasma newly = reaches old plasma membrane and new , to membrane , was area expands outwards until it fuses with it form new plant cell walls fibrils filled with middle lamella /cements (eprimary cell walls later , call walls primary together FUNCTION OF MITOSIS mitosis enables in flowering ↳ accounts growth plants and repair needed meristematic tissue for increase in lateral meristem a provides height ability before during keeps of plant as development to divide abilty long as of trees to increase as all single all grows life it lives ; located at shoot girth each growth season tip CELLS STEM most cells of adult injured tissues ↳ e - body mammalian many red bone marrow stem g . . therapeutic embryonic cloning stem cells CELL CYCLE AND is allular cancer organs human tissues be used for reproductive ↳ ↳ disorder as common - when cycle gets growth cancer out becomes develops can , , processes > - is benign can still prevent it before all possesses Normal Cells Abnormal nuclei Normal nuclei Undergo , multilayered metastasis divide blood cells of stem (causes differ cycle) not cancerous cells Undergo apoptosis Contact inhibition One widely usually , cells to fail to ability to doesn't usually , respond to from becoming spread (at this point cancerous of most or all characteristics all cancer : lack of differentiation ↳ cancer cells are not functioning tissue specialized - may characteristics but look organized layer Remain in original tissue grow bigger inhibiting signals mutation in cell can cause it to become precancerous Differentiated cells D is organized - is cancerous and has Nondifferentiated cells undergo apoptosis uncontrollably of cell cause abnormal Cancer Cells D) o not embryonic repair progression these characteristics are considered to be cancerous No contact inhibition types to cloning cells divide growth that occur malignant ↳ it can be decades ability to of control gradually many regulatory multistep abnormal cell additional mutations > - ↳ begin most adult or required but mitosis , CANCER growth follow stage different many (from due to accumulation of mutations that cause loss most cancers Go contain stem cells (retain cells divide to produce used to produce can arrested in permanently are then they cycle do not contribute to still possess very ↳ normal cells can enter cell , many normal abnormal cycle about 50 times , become unable to divide-cancer cells infinite times , are "immortal" have abnormal nuclei ↳ enlarged are , contain abnormal amount of chromosomes can (can have extra copies of one , or more chromosomes can be present ↳ often contain duplicated portions of copies of specific some chromosomes undergo ↳ cells with ↳ immune gene amplification or extra portions apoptosis damaged system DNA can apoptosis undergo recognize abnormal cells and trigger cell death - prevents usually formation tumor ↳ cause genes ↳ some chromosomes can have deleted do not , cancer cells do not undergo apoptosis , even though they are abnormal form tumors cells adhere to ↳ normal contact inhibition ↳ cancer other and ↳ Istop dividing when or anchor themselves to substratum come into contact with other they grow in aggressive multiple cell metastasis and benign tumor layers = form becomes dominant exhibit cells cells do not restrain themselves , do not have contact inhibition - pile on ↳ most undergo cells neighboring top of each a tumor cell of tumor during Carcinogenesis angiogenesis usually contained in capsule , cannot invade adjacent tissue ; additional mutations can cause it to become ↳ forms new allow tumor = ↳ now to metastasis ↳ at some to malignant- spreads throughout entire body tumors distant from , produce unusual enzymes primary tumor (these cells tissue) cells to invade travel and start new tumors underlying through blood/lymph grow through point blood vessels more , tumor become insufficient to calls need more o nutrition support rapid new blood vessels additional mutations in tumor cells allow them to direct into tumor -o angiogenesis growth of tumor, need to be growth of formed new blood vessels and inhibit cell division are essential to normal balance between signals that promote maintenance of if body tissues and two 1 . it > - types of affected usually genes by is out . Tumor 2 ↳ for proteins code suppressor proto-oncogenes Stimulus (e membrane are that inhibit normal - release starts series of Cycle (directly include proto-oncogenes promote cycle/prevent all cycle /promote cell promote that genes injury) sparks . g . cancer can apoptosis growth occur imbalance : cycle cause speed up to genes for proteins code cell promote that , mutations that can cause Proto-oncogenes ↳ of balance of apoptosis progression of cell factor- binds growth to cause cycle to slow I stop cycle to receptor protein reactions that lead to activation enzymatic of indirectly and down on plasma that genes signal molecules that make up pathways (cancer in them proto-oncogenes become oncogenes causing genes) when mutations stimulated - keep oncogenes are constantly promoting all cycle ↳ code for faulty receptor in stimulatory pathway cell is stimulated . oncogene may g abnormal product that even when there is no growth factor present; could specify uncontrolled call division stimulates Cell Cycle ↳ about 100 most family mutant forms oncogene belong to oncogenes identified associated with BRCAL (breast Cancer predisposition gene 1) hereditary forms ↳ receptors and occur ↳ e to . an or - as , -o - of breast and ovarian tumor suppressor indirectly) uncontrollably or some is prevent damaged , - genes cancer inhibit cell progression of others can even cell cycle initiate 50 % deleted genes of human p53 = when DNA O A ↑ - the cell cycle oncogene apoptosis inhibiting growth genes cycle over dividing nucleus mutation of tumor suppressor all Cycle (directly prevent cells from cancers involve gene -sturns on that inhibit cell cycle can speed up or cause &... ne s abnormal expression of factor or other apoptosis > # transcription factor - nucleus * mutations that in affect proto-oncogene cancer alls in some or , DNA repair tumor system suppressor lead to can greater of mutations chance genes mutation of telomerase enzyme (regulates , or end length telomer chromosomes) causes again telomeres to (shortened at constant stay telomeres cause happening length to makes them able to divide over of and over division halt of cell PROKARYOTIC CELL DIVISION cell division = in single-celledOrganisms produces two to offspring genetically identical parent (barring ↳ have chromosomes single > - eukaryotic - not appears enclosed ↳ When stretched out , by way dense , 2x plasma its > - Escherichia coli > - in 7 hours , has associated new than region ( 1000 x bigger cells have proteins eukaryotic = nucloid) elongation develop and than cell chromosome in electron are two chromosomes of cell pulls them grow time itself fission for , they attach to apart inward to divide cell cell wall and plasma membrane generation single cell eukaryotic that proteins shaped after DNA replication there membrane and cell wall , organelles organized differently irregularly reproduction mutations prokaryotes happens through binary enlarges original length more a sexual membrane special plasma membrane site and new , is - limited number of associated forms circular loop that is reproduction of before division , all as and DNA few proteins chromosome has bacterial chromosome asexual composed of chromosome contains micrograph individuals do not have nucleus or other membrane-bound prokaryotes Istill new each - cell When cell is about are complete (time it takes for all to divide) of about 20 minutes multiplies to 2 over million . Attachment of chromosome 1 a special plasma g to membrane site indicates that this bacterium is about to divide . & cytoplasm 2 . The cell is fission preparing for binary by enlarging its cell wall , plasma membrane and overall , volume . 3 .DNAreplicationhas producea Cell wall and plasma brane 4 . begin As the call ⑮ S g are elongates chromosomes are Cy to plasm evenly . . 5 is , the pulled apart being distributed New cell wall and membrane nave daughter mem- to grow inward. cells . plasma . binary fission each daughter and mitosis ensure that all is identical genetically to parent cell Type of Organism Cell Division Function Binary fission A sexual Mitosis and Cytokinesis Asexual reproduction Mitosis and Development , Prokaryotes Bacteria and archaea reproduction Eukaryotes Protists and some fungi /yeast) Other fungi plants , and animals , Cytokinesis growth and repair ,