Chapter 11Chapter 11

Continuity of Life:Continuity of Life:

Cellular ReproductionCellular Reproduction

Chapter 11 2

Binary FissionBinary Fission

DNA replicated

Membrane added

Chapter 11 3

Binary Fission 2Binary Fission 2

constriction

fission

Chapter 11 4

False-Color EMFalse-Color EMof Dividing Bacteriumof Dividing Bacterium

Division planeDivision plane

Cell wallCell wall

CytoplasmCytoplasm

NuclearNuclearmaterialmaterial

Chapter 11 5

Mitotic Mitotic

cell cell divisiondivision

Mitotic Mitotic cell cell division & division &

differ-differ-entiationentiation

Functions of MitosisFunctions of Mitosis

TissuesTissues

OrgansOrgansFertilized eggFertilized egg(zygote)(zygote) Multicell stageMulticell stage

Chapter 11 6

Protozoa:Protozoa:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis

New individualsNew individuals

Chapter 11 7

Yeasts:Yeasts:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis

BuddingBuddingNucleus divides by Nucleus divides by

mitosismitosisBud forms on cellBud forms on cellNucleus moves into Nucleus moves into

budbudBud separatesBud separates

Chapter 11 8

Hydra:Hydra:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis

Chapter 11 9

GeneticallyGeneticallyIdentical Aspen GrovesIdentical Aspen Groves

Three separate aspen Three separate aspen grovesgroves

Each produced Each produced asexually from single asexually from single ancestorancestor

Variable between Variable between grovesgroves

Identical within grovesIdentical within groves

Trees Trees synchronously synchronously

lost leaveslost leaves

Trees Trees synchronously synchronously

lost leaveslost leaves

Trees Trees synchronously synchronously turned yellowturned yellow

Trees Trees synchronously synchronously turned yellowturned yellow

Trees still Trees still greengreen

Trees still Trees still greengreen

Chapter 11 10

Mitosis, Meiosis,Mitosis, Meiosis,and the Sexual Cycleand the Sexual Cycle

Chapter 11 11

11 single-stranded chromosomesingle-stranded chromosome22 double helixdouble helix

uncondenseduncondensed

DNA replicationDNA replication

11 double-stranded chromosomedouble-stranded chromosome22 double helicesdouble helices

still uncondensedstill uncondensed

Chromosome Chromosome condensationcondensation

11 double-stranded chromosomedouble-stranded chromosome22 double helicesdouble helices

now condensednow condensed

centromere centromere aachromatidchromatid

cellcell basebasepairspairs

closer lookstill closer lookeven closer look

Chromosome CondensationChromosome Condensation

Chapter 11 12

HumanHumanChromosomes during MitosisChromosomes during Mitosis

Chapter 11 13

Human Karyotype, MaleHuman Karyotype, Male

These are These are chromosomes from chromosomes from mitosismitosis

Stained to show Stained to show regionsregions

Numbered by lengthNumbered by lengthOccur in pairsOccur in pairs

Chapter 11 14

telophase

metaphase

anaphase

cell

divi

sion

GG00: nondividing: nondividing

interphaseinterphase

The EukaryoticThe EukaryoticCell CycleCell Cycle

S: Synthesis S: Synthesis of DNA; of DNA; chromosomes chromosomes duplicatedduplicated

GG11: Growth: Growth

GG22: Growth: Growth

prophase

cytokinesis

Mito

sis

Chapter 11 15

Interphase : The chromosomes (blue) are in the thin, extended state and appear as a mass in the center of the cell. The microtubules (red) extend outward from the nucleus to all parts of the cell.

Metaphase: The chromosomes have moved along the spindle microtubules to the equator of the cell.

Late prophase: Chromosomes (blue) have condensed and attached to microtubules of spindle fibers (red). Microtubules have reorganized to form the spindle; chromosomes, now condensed, are clearly visible.

Phases of Mitosis, 1Phases of Mitosis, 1

Chapter 11 16

Separation of Sister ChromatidsSeparation of Sister Chromatids

In metaphase, sister chromatids In metaphase, sister chromatids are held together at centromereare held together at centromere

At end of metaphase, centromere At end of metaphase, centromere releases sister chromatidsreleases sister chromatids

In anaphase, they move to opposite In anaphase, they move to opposite polespoles

In metaphase, sister chromatids In metaphase, sister chromatids are held together at centromereare held together at centromere

At end of metaphase, centromere At end of metaphase, centromere releases sister chromatidsreleases sister chromatids

In anaphase, they move to opposite In anaphase, they move to opposite polespoles

Chapter 11 17

Anaphase: Sister chromatids have separated, and one set of chromosomes moves along the spindle microtubule to each pole of the cell.

Telophase: The chromosomes have gathered into two clusters, one at the site of each future nucleus.

Next interphase: Chromosomes are relaxing again into their extended state. Spindle fibers are disappearing, and the microtubules of the 2 daughter cells rearrange into the interphase pattern.

Phases of Mitosis, 2Phases of Mitosis, 2

Chapter 11 18

Mitosis:Mitosis:Prophase - MetaphaseProphase - Metaphase

Kinetochores align at cell’s

equator

Nucleolus disappears;

Nuclear envelope breaks down

Microtubules attach to

kinetochores

Chromosomes condense and

shorten

Centrioles begin to move apart;Spindle forms

Duplicated chromosomes

remain elongated

Centrioles have also been duplicated

LateLateInterphaseInterphase

EarlyEarlyProphaseProphase

LateLateProphaseProphase MetaphaseMetaphase

Chapter 11 19

MitosisMitosisAnaphase - CytokinesisAnaphase - Cytokinesis

Free spindle fibers push poles apart

Chromatids become

independent chromosomes

One set of chromosomes;

Begin unwinding

Nuclear envelope re-

forms

Cytoplasm divided along

equator

Each daughter gets 1 nucleus &

half of cytoplasm

Spindle disappears; Nucleolus reappears

AnaphaseAnaphase TelophaseTelophase CytokinesisCytokinesisNextNext

InterphaseInterphase

Chapter 11 20

Cytokinesis of a Ciliated CellCytokinesis of a Ciliated Cell

Cleavage FurrowCleavage Furrow

Daughter CellsDaughter Cells

Chapter 11 21

Cytokinesis in PlantsCytokinesis in Plants

Vesicles fuse to form cell wall

and membranesComplete

separation of daughter cells

Chapter 11 22

Meiosis IMeiosis IHomologous

chromosomes pair and cross over

Homologous chromosomes

exchange DNA & align on equator

Homologous chromosomes move to

opposite poles

Prophase IProphase I Metaphase IMetaphase I Anaphase IAnaphase I Telophase ITelophase I

Chapter 11 23

Meiosis IIMeiosis II

Prophase IIProphase II Metaphase IIMetaphase II Anaphase IIAnaphase II Telophase IITelophase IIFourFour

HaploidHaploidCellsCells

Similar to MitosisSimilar to Mitosis

Chapter 11 24

Crossing OverCrossing Over

Homologues Homologues pair uppair up

Protein strands Protein strands zip togetherzip together

Recombination Recombination enzymes snip enzymes snip and rejoin and rejoin DNADNA

Homologs Homologs separate with separate with new gene new gene combinationscombinations

Chapter 11 25 Meiosis vs. Mitosis:Meiosis vs. Mitosis:

Comparison of SpindlesComparison of SpindlesMeiosis: Duplicated chromosomes Meiosis: Duplicated chromosomes with one kinetochore; Paired with one kinetochore; Paired homologues go to opposite poles.homologues go to opposite poles.

Meiosis: Duplicated chromosomes Meiosis: Duplicated chromosomes with one kinetochore; Paired with one kinetochore; Paired homologues go to opposite poles.homologues go to opposite poles.

Mitosis: Duplicated chromosomes Mitosis: Duplicated chromosomes with two kinetochores; Unpaired with two kinetochores; Unpaired homologs split between sister homologs split between sister chromatids, which go to opposite chromatids, which go to opposite poles.poles.

Mitosis: Duplicated chromosomes Mitosis: Duplicated chromosomes with two kinetochores; Unpaired with two kinetochores; Unpaired homologs split between sister homologs split between sister chromatids, which go to opposite chromatids, which go to opposite poles.poles.

Chapter 11 26 Meiosis vs. Mitosis:Meiosis vs. Mitosis:

Comparison of StagesComparison of Stages

Chapter 11 27

Metaphase Alignment ScenariosMetaphase Alignment Scenarios

Chapter 11Chapter 11

The endThe end