Mader/Biology Mader/Biology , 11/e – Chapter Outline Chapter 9 9.1
The Ce Cell Cy Cycle 1. The cell cycle is is an orderly set of stages from from the rst division to the time time the daughter cells divide. cells divide. 2. When a cell is preparing preparing for division, it grows grows larger, the number number of organelles doubles, and the DN replicates. . !nterp !nterpha hase se 1. "ost of a cell#s life is spent in interphase, in interphase, in which the cell performs its usual functions. 2. Time ime spe spent nt in inte interp rpha hase se vari varies es by cell cell type type$$ ner nerve ve and and mus muscl cle e cel cells ls do not complete the cell cycle and remain in the G0 stage while embryonic cells complete the cycle every few hours. %. The G1 stage is &ust prior to DN replication' a cell grows in si(e, organelles increase in number, and material accumulates for DN synthesis. ). The S stage is the DN synthesis *replication+ period' proteins proteins associated with DN are also synthesi(ed' at the end of the stage, each chromosome has two identical DN double helimolecules, called sister chromatids. chromatids . . The G2 stage occurs &ust prior to cell division' the cell synthesi(es proteins needed for cell division, such as proteins in microtubules. /. !nterphas !nterphase e therefor therefore e consists consists of 0 1, , and 0 2. . " *"i *"ito toti tic+ c+ tag tage e 1. M stage (" it!sis+ it!sis+ is the entire cell division stage, including both mitosis and cyto3inesis. 2. Mit!sis is nuclear division, cyt!"inesis is cyt!"inesis is division of the cytoplasm. %. When division division of the cytoplasm is is complete, complete, two daughter cells are cells are produced. 4. 4ontr 4ontrol ol of the 4ell 4ell 4ycl 4ycle e 1. signal is an agent that in5uences the activities of a cell. 2. Gr!#th $act!rs are $act!rs are e-ternal signals received at the plasma membrane. %. 4ell 4ell 4ycle 4ycle 4hec3p 4hec3poin oints ts a. There are are three chec3points chec3points where where the cell cycle either either stops or continues continues onward, depending on the internal signals it receives. cyclins, internal b. 6esearchers have identied a family of proteins called cyclins, signals that increase or decrease during the cell cycle. c. 4yclin must must be present present for the cell to move from from the 0 1 stage to the stage, and from the 0 2 stage to the " stage. d. The primary primary chec3point chec3point of the cell cell cycle cycle is the the 0 1 chec3point. e. DN damage damage stops stops the the cycle cycle at the 01 chec3point by the protein p%&' p%&' if the DN is not repaired, p% triggers ap!pt!sis. f. n not othe herr prot protei ein, n, ' ' * *r r etinob etinoblastoma+, is responsible for interpreting growth and nutrient availability signals. g. The cell cell cycle cycle stops stops at the the 0 2 stage if DN has not nished replicating' replicating' stopping the cell cycle at this stage allows time for repair of possible damaged DN. h. lso, the cycle stops stops if chromosomes chromosomes are not properly properly attached to the it!tic spindle. D. popto optos sis 1. poptosis poptosis is is progra programmed mmed cell cell death death and involv involves es a se7uenc se7uence e of cellula cellularr
events involving$ a. 8ragmenting of the nucleus, nucleus, b. listering of of the plasma membrane, and c. 9ngulng of cell fragments fragments by macrophages macrophages and:or nei neighboring ghboring cells. 2. p popt optosi osis s is caus caused ed by by en(ym en(ymes es call called ed caspases. caspases . a. 4ells normally hold caspases in chec3 with inhibitors. b. 4aspases are released by internal or e-ternal signals. %. poptosis poptosis and and cell division division are are balancing balancing proces processes ses that that maintain maintain the normal normal level of s!atic *body+ s!atic *body+ cells. ). 4ell death death is a norma normall and necessar necessary y part of developm development$ ent$ frogs, frogs, for e-amp e-ample, le, must destroy tail tissue they used as tadpoles, and the human embryo must eliminate webbing found between ngers and toes. . Death Death by apopt apoptosis osis prev prevents ents a tumor from developi developing. ng. 9. The 01 4hec3point *Nature *Nature of Science reading+ Science reading+ 1. During cell division, division, only certain certain cells in an adult adult body are actively actively dividing. dividing. 2. ;nce cell division occurs, occurs, cells cells enter 0 1 stage. %. 8ollo 8ollowin wing g the the 01 stage, cells enter the 0 1 chec3point to ma3e sure that the correct conditions occur to continue cell division. ). 9valuati 9valuating ng 0rowth 0rowth ignals ignals a. ignal molecules molecules are are sent to to encourage encourage or discourage discourage cells cells from from entering the cell cycle. 4ells may enter a 0 < stage, complete 0 1 and enter stage. b. 4ell division division promoting promoting signals can cause cause a cyclin=dependent=3inase cyclin=dependent=3inase *4D>+ to add a phosphate group to 6, which is a regulator of the 01 chec3point. c. When 6 is phosphorylated, phosphorylated, the shape of 6 changes changes and it releases releases the protein 928, rather than binding to 928. d. 928 then binds to DN DN and activates genes to complete the the cell cycle. e. !f growth growth signals are su?cient, a cell will pass pass through through the 0 1 chec3point and cell division will occur. . Determining Determining Nutrient Nutrient vailability vailability a. 4ells re7uire re7uire ade7uate nutrient levels prior to cell division. b. When nutrients nutrients are are available, available, 4D>s bring about about phosphorylation phosphorylation of 6, which releases 928. 928 binds to DN to produce proteins. c. When nutri nutrients ents are are not availabl available, e, the cell cell enters enters the 0 < stage and does not progress to the 0 1 stage. /. ssessin ssessing g DN !ntegr !ntegrity ity a. DN must be free of error errors s and damage damage in order for cell division division to occur. b. !f DN damage damage is detected, 4D> phosphorylates phosphorylates p%. 6ather than being bro3en down, p% levels in the nucleus rise. c. The phosphorylated phosphorylated p% p% binds to DN to produce produce DN repair proteins. proteins. d. !f DN damage damage cannot cannot be repaired repaired,, p% levels levels continue continue to rise to trigger apoptosis. @owever, if DN damage is repaired, p% levels fall, and cell completes 0 1 stage as long as other re7uirements are met. 9.2 9.2 Mit! Mit!si sis s and and Cyt! Cyt!"i "in nesis esis . 9u3aryo 9u3aryotic tic 4hromoso 4hromosomes mes 1. DN in chromosom chromosomes es of eu3aryotic eu3aryotic cells cells is associa associated ted with protein proteins' s' hist!nes organi(e chromosomes. 2. When a cell cell is not under undergoing going divisi division, on, DN in the the nucleus nucleus is a tangle tangled d mass of threads called chr!atin. %. t cell cell division, division, chromatin chromatin becomes becomes highly highly coiled and condensed condensed and and is now visible as individual chromosomes. chromosomes. ). 9ach specie species s has a charact characteris eristic tic number number of chromosom chromosomes. es.
a.
The dipl!id (2n) number (2n) number includes two sets of chromosomes of each type.
1+ The diploid number is found in all the non=se- cells cells of an organism#s body *with a few e-ceptions+. e-ceptions+. b. The hapl!id (n) number (n) number contains one of each 3ind of chromosome. chromosome. 1+!n the life cycle of many animals, only sperm and egg cells have the haploid number. . Arepar Areparatio ations ns for "itosis "itosis 1. 4ell division division in eu3aryotes eu3aryotes involves nuclear division and cyto3inesis. cyto3inesis. a. omatic omatic cells cells under undergo go mitosi mitosis s for development, growth, and repair. 1+ This nuclear nuclear division division leaves leaves the chromosom chromosome e number constant constant.. 2+ 2n nucleus nucleus replicates replicates and divides to provide provide daughter daughter nuclei that are also 2n. b. chromosom chromosome e begins begins cell cell division division with with two sister chromatids. chromatids . 1+ Sister chromatids are chromatids are two strands of genetically identical chromosomes. 2+ t the beginning of cell division, division, they are attached attached at a centr!ere, a centr!ere, a region of constriction on a chromosome. %+ *inet!ch!res are *inet!ch!res are protein comple-es that develop on either side of the centromere during cell division 2.
The centr!s!e, centr!s!e, the main microtubule microtubule organi(ing center of the cell, divides before mitosis begins.
%. 9ach centrosome centrosome contains a pair of barrel=sha barrel=shaped ped organelles organelles called centri!les. ). The mitotic spindle contains many bers, each composed of a bundle of
microtubules. microtubules.
. "icrotubu "icrotubules les are are made of the the protein protein tu+ulin. a. "icrotubules "icrotubules assemble when when tubulin subunits subunits &oin, disassemble disassemble when tubulin subunits become free, and form interconnected laments of cytos3eleton. cytos3eleton. b. "icrotubu "icrotubules les disass disassembl emble e as spindle spindle bers bers form form.. 4. Ahases Ahases of "itosis "itosis 1. "itosis "itosis is divided divided into ve phases$ phases$ prophas prophase, e, prometap prometaphase hase,, metaphase, metaphase, anaphase, anaphase, and telophase. 2. Arophase a. Nucle Nuclear ar divisi division on is is abou aboutt to occur occur$$ chro chroma matin tin conden condenses ses and and chromosomes become visible. b. The nucleo nucleolus lus dis disap appea pears rs and and the the nuc nuclea learr enve envelop lope e fragm fragment ents. s. c. Duplic Duplicat ated ed chr chromos omosome omes s are are compo composed sed of two two sis sister ter chro chromat matids ids held held together by a centromere' chromosomes chromosomes have no particular orientation in the cell at this time.
d.
The spi spindl ndle e begin begins s to asse assembl mble e as pair pairs s of cent centro rosom somes es migr migrate ate away away from each other. e. n arra array y of of micr microt otub ubul ules es call called ed asters radiates toward the plasma membrane from the centrosomes. %. Arome Arometap tapha hase se *Bate *Bate Aro Aropha phase+ se+ a. peciali peciali(ed (ed protein protein complecomple-es es * "inet!ch!res+ "inet!ch!res+ develop on each side of the centromere for future chromosome orientation. b. n important event event during prometaphase prometaphase is attachment of the the chromosomes to the spindle and their movement as they align at the metaphase plate *e7uator+ of the spindle. c. The 3inetochores 3inetochores of sister chromatids chromatids capture capture kinetochore spindle bers. bers . d. 4hromosomes move bac3 and and forth toward toward alignment at at the metaphase metaphase plate. ). "eta ). etapha phase a. 4hromo 4hromosom somes es,, attac attached hed to to 3ineto 3inetocho chore re ber bers, s, are are now now align aligned ed at at the etaphase plate. b. Non= Non=at atta tach ched ed spin spindl dle e ber bers, s, call called ed polar polar spindle spindle bers, bers, can reach beyond the metaphase plate and overlap. c. ce cell ch chec3p ec3po oint int ca called the the M checkpoint delays delays the start of anaphase until 3inetochores are properly attached to the spindle bers, and chromosomes are properly aligned along metaphase plate. . naphase a. The two two siste sisterr chro chroma matid tids s of each each dupli duplica cated ted chr chromo omosom some e separ separate ate at at the centromere. b. Daugh Daughter ter chro chromos mosome omes, s, each each with with a centro centromer mere e and single single chro chromat matid, id, move to opposite poles. 1+ Aolar spindle spindle bers lengthen as they slide past each other. other. 2+ >inetochore >inetochore spindle bers disassemble at the 3inetochores' 3inetochores' this pulls daughter chromosomes to poles. %+ The motor motor molecules molecules kinesin and kinesin and dynein are dynein are involved in this sliding process. )+ naphase is the the shortest stage of mitosis. mitosis. /. Telop eloph hase a. pin pindl dle e dis disap appe pear ars s in in thi this ss sta tage ge.. b. The nucl nuclear ear envelo envelope pe refo reform rms s aroun around d the dau daught ghter er chro chromos mosome omes. s. c. The daught daughter er chr chromo omosom somes es diCu diCuse, se, again again formin forming g chro chromat matin. in. d. The nucleo nucleolus lus reapp reappear ears s in each each daugh daughter ter nucleu nucleus. s. D. 4yto3inesis in in nimal and and Alant 4ells 4ells 1. 4yto3ines 4yto3inesis is in nimal nimal 4ells 4ells a. cleaage $urr!# indents $urr!# indents the plasma membrane between the two daughter nuclei at a midpoint' this deepens to divide the cytoplasm during cell division. b.
4ytopl 4ytoplasm asmic ic cleava cleavage ge begins begins as anapha anaphase se draws draws to a clos close e and and organelles are distributed.
c.
The cleava cleavage ge fur furro row w deepe deepens ns as a ban band d of actin actin lam lament ents, s, called called the contractile ring, ring , constricts between the two daughter cells.
d.
narr narrow ow brid bridge ge e-is e-ists ts betw between een daugh daughter ter cells cells during during teloph telophas ase e until until constriction completely separates the cytoplasm.
2. 4yto3ines 4yto3inesis is in Alant Alant 4ells 4ells a. The rigid rigid cell cell wall wall tha thatt surro surround unds s plan plantt cells cells does does not per permit mit cyto3i cyto3ines nesis is
by furrowing. b. The 0olgi 0olgi appara apparatus tus produ produces ces vesicl vesicles, es, which which move move alon along g the the microtubules microtubules to a small 5attened disc that has formed. c. esicles fuse forming a cell plate- their plate- their membranes complete the plasma membranes of the daughter cells. d. The new membra membrane ne also also relea releases ses molecu molecules les from from the the new plant plant cell cell walls' the cell walls are strengthened by the addition of cellulose brils. 9. The 8unctio unctions ns of "itosi "itosis s 1. "itosis permits permits growth growth and repair repair.. 2. !n 5owering plants, the meristematic tissue retains tissue retains the ability to divide throughout the life of the plant' this accounts for the continued growth, both in height and laterally, of a plant.
%. !n mammals, mitosis mitosis is necessary necessary as a fertili(ed fertili(ed egg becomes becomes an embryo and as the embryo becomes a fetus' throughout life, mitosis allows a cut to heal or a bro3en bone to mend. 8. tem tem 4el 4ells ls 1. "any mammal mammalian ian organs organs contain contain stem cells *or adult stem cells+, cells +, which retain the ability to divide. 2. 6ed bone marrow marrow stem cells repeatedly repeatedly divide divide to produce the various types of blood cells. %. Therapeutic cl!ning to cl!ning to produce human tissues can begin with either adult stem cells or embryonic stem cells. ). 9mbryonic 9mbryonic stem stem cells cells can be used used for repr!ductie cl!ning, the cl!ning, the production of a new individual. 0. 6eproduct eproductive ive and and Therapeut Therapeutic ic 4loning 4loning *Nature * Nature of Science reading+ Science reading+ 1. There are two types of cloning$ cloning$ reproductive reproductive cloning and therapeutic therapeutic cloning. cloning. 2. 6epro 6eproducti ductive ve *soma *somatic tic cell+ cell+ cloning cloning a. !n reproductive reproductive cloning, the donor cells cells are are rst starved, starved, then the nucleus is ta3en out of cell and transplanted into enucleated egg. b.
The The don donor or cell cell stop stops s div divid idin ing g and and goes goes into into 0 < stage.
c.
9mbr 9mbryo yoni nic c stem stem cel cells ls ar are form formed ed and and imp impla lant nted ed int into o the the embr embryo yo of of a surrogate mother.
d.
When embryo is fully developed, a clone is born.
%. Ther Therap apeu euti tic c clon clonin ing g a.
b.
;ne ;ne way way to conduc conductt thera therapeu peutic tic cloni cloning ng is is by by the the same same proce procedur dure e as reproductive cloning, embryonic stem cells are separated and sub&ected to treatment that causes it to develop into diCerent types of cells$ red blood cells, muscle cells, nerve cells.
The The oth other er way way to to con condu duct ct ther therap apeu euti tic c clo cloni ning ng is to use use adult stem cells. cells . c.
;ne ;ne dra drawba wbac3 c3 to using using adult adult stem stem cell cells s is is they they are are limi limited ted in the number of cell types they may become. @owever, researchers are trying to overcome this obstacle.
9.&
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The Cell Cycle and Cancer 1. Cancer is a cellular growth disorder that occurs when cells divide uncontrollably' i.e., cancer results from the loss of control and a disruption of the cell cycle. 2. "ost cancers begin as abnormal cell cell growth growth that is +enign, or +enign, or not cancerous %. When additional additional mutations mutations occur, occur, the growth growth becomes alignant, or alignant, or cancerous, and possesses the ability to spread. . 4haracteristics 4haracteristics of 4ancer 4ancer 4ells 1. 4ancer cells lac3 diCerentiation. diCerentiation. a. Enli3 Enli3e e norm normal al cell cells s that that diCe diCere renti ntiate ate into into muscle muscle or nerv nerves es cell cells, s, canc cancer er cells have an abnormal form and are nonspeciali(ed. b. Norma Normall cells cells enter enter the the cell cell cycle cycle only only about about < < times times'' cance cancerr cells cells are are immortal in that they can enter the cell cycle repeatedly. 2. 4ancer cells have abnormal nuclei. a. The nuclei nuclei may may be enlar enlarged ged and and may may have have an an abnor abnormal mal numbe numberr of chromosomes. b. The chromo chromosom somes es hav have e mutat mutated' ed' some some chro chromos mosome omes s may may be duplicated or deleted. %. 4ancer 4ancer cells cells do do not not under undergo go apopto apoptosis sis a. Wher Wherea eas s ordina ordinary ry cells cells with with DN DN dama damage ge under undergo go apopt apoptosi osis, s, cance cancerr cells do not. ). 4ance 4ancerr cel cells ls for form m tumor tumors. s. a. Norma Normall cells cells are are ancho anchore red d and and stop stop divi dividin ding g when when in in conta contact ct with with other other cells' i.e., they e-hibit contact inhibition. inhibition . b. 4ance 4ancerr cells cells inva invade de and and destr destroy oy norm normal al tissu tissue e and thei theirr growt growth h is not not inhibited. c. 4anc 4ancer er cell cells s pil pile e on top top of each each othe otherr to to form form a tu!r. . 4ancer cells cells undergo undergo metastasis metastasis and and angiogenesis. angiogenesis. a. benign tumor is is encapsulated encapsulated and does not invade ad&acent tissue. b. "any type types s of of ca cancer cer ca can un underg ergo etastasis, in etastasis, in which new tumors form which are distant from the primary tumor. c. ngi!genesis, the ngi!genesis, the formation of new blood vessels, is re7uired to bring nutrients and o-ygen to the tumor. ;rigin of 4ancer 1. r!t!!nc!genes code r!t!!nc!genes code for proteins that stimulate the cell cycle and prevent apoptosis. 2. Tu!rsuppress!r genes code genes code for proteins that inhibit the cell cycle and promote apoptosis. %. "utations "utations of either either of these these genes genes can cause cause cancer cancer.. ). Aroto=o Aroto=onco ncogen genes es are are at at the end end of a stimulatory pathway from from the plasma membrane to the nucleus' a growth factor binding at the plasma membrane can result in turning on an oncogene. . Aroto=onco Aroto=oncogene genes s can can underg undergo o mutation mutation to become become !nc!genes *cancer= !nc!genes *cancer= causing genes+. /. n oncogene may code for a faulty faulty receptor receptor in the stimulatory stimulatory pathway pathway.. F. ;r an oncogene can can specify an abnormal abnormal protein protein product or abnormally abnormally high levels of a normal product that stimulates the cell cycle. G. Tumor=supp umor=suppre ressor ssor genes genes are are at the end of an inhibitory pathway ' a growth= inhibitory factor can result in turning on a tumor suppressor gene that inhibits the cell cycle. H. The balance balance between between stimulat stimulatory ory and inhibitory inhibitory signals signals deter determines mines whether proto=oncogenes or tumor=suppressor genes are active, and therefore whether or not cell division occurs. 1<. 6esearch esearchers ers have have identie identied d about about a half do(en do(en tumor tumor=supp =suppres ressor sor genes genes..
11.
12.
1%.
The RB tumor=suppressor RB tumor=suppressor gene prevents retinoblastoma, a cancer of the retina, and has been found to malfunction in cancers of the breast, prostate, bladder, and small=cell lung carcinoma. The p53 tumor=suppressor p53 tumor=suppressor gene is more fre7uently mutated in human cancers than any other 3nown gene' it normally functions to trigger cell cycle inhibitors and stimulate apoptosis. !n some some cance cancerr cells, cells, mutation mutation of an an en(yme en(yme that regula regulates tes the the lengt length h of tel!eres causes tel!eres causes the telomeres telomeres to remain remain at a constant length, which allows the cancer cells to continue dividing.
9. r!"ary!tic Cell iisi!n 1. Enicellular organisms organisms reproduce reproduce via ase3ual repr!ducti!n, in repr!ducti!n, in which the oCspring are genetically identical to the parent. . The Aro3ar Aro3aryotic yotic 4hromoso 4hromosome me 1. Aro3aryotic Aro3aryotic cells *bacteria *bacteria and archaea+ archaea+ lac3 a nucleus and other membranous membranous organelles. 2. The pro3aryotic pro3aryotic chromosome chromosome is composed of DN and and associated proteins, proteins, but much less protein than eu3aryotic chromosomes. %. The chrom chromosome osome appea appears rs as a nucle!id, an irregular=shaped region that is not enclosed by a membrane. ). The chromosome chromosome is a circular circular loop attached to the inside inside of the plasma membrane' it is about 1,<<< times the length of the cell. . inary inary 8issi ission on 1. inary 4ssi!n of 4ssi!n of pro3aryotic cells produces two genetically identical daughter cells. 2. efore cell cell division, DN is is replicatedIboth replicatedIboth chromosomes chromosomes are attached attached to a special site inside the plasma membrane. %. The two chromosomes chromosomes separate as as a cell lengthens lengthens and pulls them apart. apart. ). When the cell is appro-imately appro-imately twice its original length, length, the plasma membrane membrane grows inward, a septum *consisting of new cell wall and plasma membrane+ forms, dividing the cell into two daughter cells. . The generation time time of bacteria depends depends on the species and and environmental environmental conditions' Escherichia coli#s coli #s generation time is about 2< minutes. 4. 4omparing Aro3aryotes Aro3aryotes and and 9u3aryotes 9u3aryotes 1. oth binary ssion ssion and mitosis ensure ensure that each daughter daughter cell is genetically genetically identical to the parent. 2. acteria and protists protists use ase-ual ase-ual reproduction reproduction to produce identical oCspring. oCspring. %. !n multicellular multicellular fungi, plants, plants, and animals, animals, cell division is part part of the growth process that produces and repairs the organism. ). Aro3aryotes Aro3aryotes have a single chromosome chromosome with mostly DN and and some associated associated protein' there is no spindle apparatus.
. 9u3aryotic 9u3aryotic cells have chromosomes chromosomes with DN and and many associated associated proteins' histone proteins histone proteins organi(e the chromosome. /. The spindle is involved involved in distributing distributing the daughter chromosomes chromosomes to the daughter nuclei.
