Cell CycleCell Cycle

Chapter 12~ Chapter 12~ The Cell The Cell

CycleCycle

Cell Division: Key RolesCell Division: Key Roles Genome: cell’s genetic informationGenome: cell’s genetic information Somatic (body cells) cellsSomatic (body cells) cells Gametes (reproductive cells): Gametes (reproductive cells):

sperm and egg cellssperm and egg cells Chromosomes: DNA moleculesChromosomes: DNA molecules Diploid (2n): 2 sets of chromosomes Diploid (2n): 2 sets of chromosomes Haploid (1n): 1 set of chromosomesHaploid (1n): 1 set of chromosomes Chromatin: DNA-protein complexChromatin: DNA-protein complex Chromatids: replicated strands of a Chromatids: replicated strands of a

chromosomechromosome Centromere: narrowing “waist” of Centromere: narrowing “waist” of

sister chromatidssister chromatids Mitosis: nuclear divisionMitosis: nuclear division Cytokinesis: cytoplasm divisionCytokinesis: cytoplasm division Meiosis: gamete cell divisionMeiosis: gamete cell division

Centromere

Centriols

Sister Chromotides

Chromosome

Spindle fibers

The Cell CycleThe Cell Cycle

Interphase Interphase (90% of cycle)(90% of cycle) • G1 phase~ growth • G1 phase~ growth

• S phase~ • S phase~ synthesis of DNA • G2 synthesis of DNA • G2 phase~ preparation for phase~ preparation for

cell divisioncell division Mitotic phaseMitotic phase

• Mitosis~ nuclear • Mitosis~ nuclear division • Cytokinesis~ division • Cytokinesis~ cytoplasm cytoplasm divisiondivision

MitosisMitosis

ProphaseProphase PrometaphasePrometaphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

ProphaseProphase

Chromosomes Chromosomes visiblevisible

Nucleoli Nucleoli disappeardisappear

Sister chromatidsSister chromatids Mitotic spindle Mitotic spindle

formsforms Centrosomes Centrosomes

movemove

MetaphaseMetaphase

Centrosomes at Centrosomes at opposite polesopposite poles

Centromeres are Centromeres are alignedaligned

Kinetochores of Kinetochores of sister chromatids sister chromatids attached to attached to microtubules microtubules (spindle)(spindle)

AnaphaseAnaphase

Paired centromeres Paired centromeres separate; sister separate; sister chromatids chromatids liberatedliberated

Chromosomes move Chromosomes move to opposite polesto opposite poles

Each pole now has a Each pole now has a complete set of complete set of chromosomeschromosomes

TelophaseTelophase

Daughter nuclei Daughter nuclei formform

Nuclear Nuclear envelopes ariseenvelopes arise

Chromatin Chromatin becomes less becomes less coiledcoiled

Two new nuclei Two new nuclei complete mitosiscomplete mitosis

CytokinesisCytokinesis

Cytoplasmic Cytoplasmic divisiondivision

Animals: Animals: cleavage cleavage

furrowfurrow Plants: Plants:

cell platecell plate

The reasons that cells divide.The reasons that cells divide.• The larger the cell the more demands The larger the cell the more demands

the cell places on its DNA. the cell places on its DNA. • The second reason is it has a harder The second reason is it has a harder

time moving enough nutrients and time moving enough nutrients and wastes across the membrane.wastes across the membrane.

DNA doesn’t copy itself except for DNA doesn’t copy itself except for during cell divisionduring cell division

Why Division

Cell Cycle regulationCell Cycle regulation

Growth factors- Growth factors- protein that helps protein that helps stimulate divisionstimulate division

Density-dependent Density-dependent inhibition-crowded inhibition-crowded cells stop dividingcells stop dividing

Anchorage Anchorage dependence- must dependence- must be attached to be attached to somethingsomething

RegulatorsRegulators

These help tell cells when to divide and These help tell cells when to divide and when to stop or to not divide at all.when to stop or to not divide at all.

These are proteins that regulate cell These are proteins that regulate cell division. They are called Cyclins.division. They are called Cyclins.

There are 2 types of regulators internal There are 2 types of regulators internal and external growth factors.and external growth factors.

Cancer is uncontrolled cell growth. Cancer is uncontrolled cell growth. Because it doesn’t respond to internal Because it doesn’t respond to internal growth factors or external growth growth factors or external growth factorsfactors

InternalInternal growth factors- are proteins that growth factors- are proteins that respond to events inside the cell. respond to events inside the cell. • They don’t let it divide till all the They don’t let it divide till all the

chromosomes have been copiedchromosomes have been copied• Don’t let it go into anaphase until the Don’t let it go into anaphase until the

spindle fibers are attached spindle fibers are attached External growth factors- proteins that External growth factors- proteins that

respond to events outside the cell.respond to events outside the cell.• Tell it to speed up or slow down the cell Tell it to speed up or slow down the cell

cyclecycle• Growth factors stimulate cell growth and Growth factors stimulate cell growth and

division of cells.division of cells.• Another are molecules found on the Another are molecules found on the

surface of neighboring cells that tell the surface of neighboring cells that tell the cell to slow down or stop dividingcell to slow down or stop dividing

• These prevent excessive cell growthThese prevent excessive cell growth

CancerCancer

Transformation- change from a Transformation- change from a normal cell to cancernormal cell to cancer

Tumor: benign or malignantTumor: benign or malignant Metastasis- moveMetastasis- move

Binary FissionBinary Fission

How How prokaryotes prokaryotes replicatereplicate

Origin of Origin of replicationreplication