Download - AP Bio Ch11 PowerPoint
Chapter 11Chapter 11
Continuity of Life:Continuity of Life:
Cellular ReproductionCellular Reproduction
Chapter 11 2
Cellular ReproductionCellular Reproduction
Intracellular activity between one cell division Intracellular activity between one cell division to the next is the to the next is the cell cyclecell cycle
• Some activities involve growth (enlargement) Some activities involve growth (enlargement) of the cellof the cell
• Some activities involve duplication of genetic Some activities involve duplication of genetic material and cellular division (reproduction)material and cellular division (reproduction)
Binary Fission (prokaryotes)Binary Fission (prokaryotes)Mitosis (new individual cells)Mitosis (new individual cells)
Budding (eukaryotes)Budding (eukaryotes)Meiosis (new gametes)Meiosis (new gametes)
Chapter 11 3
The Prokaryotic Cell CycleThe Prokaryotic Cell Cycle
1.1. Long growth phaseLong growth phase– Replication of circular DNA chromosome occursReplication of circular DNA chromosome occurs– Duplicate chromosomes anchored to membraneDuplicate chromosomes anchored to membrane
2.2. Cell increases in size, pulling duplicated Cell increases in size, pulling duplicated chromosomes apart…chromosomes apart…
3.3. Plasma membrane grows inward between Plasma membrane grows inward between chromosome copieschromosome copies
4.4. Fusion of membrane along cell equator Fusion of membrane along cell equator completes separation (completes separation (binary fissionbinary fission or “splitting or “splitting in two”)…in two”)…
5.5. Daughter cells are genetically identicalDaughter cells are genetically identical• Under ideal conditions Under ideal conditions Escherichia coliEscherichia coli bacteria bacteria
complete a cell cycle every 20 minutescomplete a cell cycle every 20 minutes
Chapter 11 4
Binary FissionBinary Fission
DNA replicated
Membrane added
Chapter 11 5
Binary Fission 2Binary Fission 2
constriction
fission
Chapter 11 6
False-Color EMFalse-Color EMof Dividing Bacteriumof Dividing Bacterium
Division planeDivision plane
Cell wallCell wall
CytoplasmCytoplasm
NuclearNuclearmaterialmaterial
Chapter 11 7
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 8
Protozoa:Protozoa:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis
New individualsNew individuals
Chapter 11 9
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 10
Hydra:Hydra:Asexual Reproduction by MitosisAsexual Reproduction by Mitosis
Chapter 11 11
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 12
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 13
HumanHumanChromosomes during MitosisChromosomes during Mitosis
Chapter 11 14
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 15
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 16
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 17
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 18
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 19
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 20
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 21
Cytokinesis of a Ciliated CellCytokinesis of a Ciliated Cell
Cleavage FurrowCleavage Furrow
Daughter CellsDaughter Cells
Chapter 11 22
Cytokinesis in PlantsCytokinesis in Plants
Vesicles fuse to form cell wall
and membranesComplete
separation of daughter cells
Chapter 11 23
Control of Cell CycleControl of Cell Cycle
The cells of some tissues divide frequently The cells of some tissues divide frequently throughout lifespanthroughout lifespan
– e.g. skin, intestine e.g. skin, intestine
Cell division occurs rarely or not at all in other Cell division occurs rarely or not at all in other tissuestissues
– e.g. brain, heart, skeletal musclese.g. brain, heart, skeletal muscles
Cell division in eukaryotes is driven by Cell division in eukaryotes is driven by enzymes and controlled at specific enzymes and controlled at specific checkpointscheckpoints
Chapter 11 24
Enzymes Drive the Cell CycleEnzymes Drive the Cell Cycle
• The cell cycle is driven by proteins The cell cycle is driven by proteins called called CCyclin-yclin-ddependent ependent kkinases, or inases, or Cdk’s Cdk’s
• Kinases are enzymes that phosphorylate Kinases are enzymes that phosphorylate (add a phosphate group to) other (add a phosphate group to) other proteins, stimulating or inhibiting their proteins, stimulating or inhibiting their activity activity
• Cdk’s are active only when they bind to Cdk’s are active only when they bind to other proteins called cyclinsother proteins called cyclins
Chapter 11 25
Enzymes Drive the Cell CycleEnzymes Drive the Cell Cycle
• Cell division occurs when Cell division occurs when growth growth factorsfactors bind to cell surface receptors, bind to cell surface receptors, which leads to cyclin synthesis which leads to cyclin synthesis
• Cyclins then bind to and activate Cyclins then bind to and activate specific Cdk’sspecific Cdk’s
Chapter 11 26
Enzymes Drive the Cell CycleEnzymes Drive the Cell Cycle
• Activated Cdk’s promote a variety of cell Activated Cdk’s promote a variety of cell cycle eventscycle events– Synthesis and activation of proteins required Synthesis and activation of proteins required
for DNA synthesisfor DNA synthesis– Chromosome condensationChromosome condensation– Nuclear membrane breakdownNuclear membrane breakdown– Spindle formationSpindle formation– Attachment of chromosomes to spindleAttachment of chromosomes to spindle– Sister chromatid separation and movementSister chromatid separation and movement
Chapter 11 27
Chapter 11 28
Checkpoints Control Cell CycleCheckpoints Control Cell Cycle• Although Cdk’s drive the cell cycle, multiple Although Cdk’s drive the cell cycle, multiple
checkpoints ensure that…checkpoints ensure that…– The cell successfully completes DNA synthesis The cell successfully completes DNA synthesis
during interphase during interphase – Proper chromosome movements occur during Proper chromosome movements occur during
mitotic cell divisionmitotic cell division • There are three major There are three major checkpointscheckpoints in the in the
eukaryotic cell cycle, each regulated by eukaryotic cell cycle, each regulated by protein complexesprotein complexes
1.1. G1 to S: G1 to S: 2.2. G2 to mitosisG2 to mitosis3.3. Metaphase to anaphaseMetaphase to anaphase
Chapter 11 29
Chapter 11 30
Checkpoints Control Cell CycleCheckpoints Control Cell Cycle
• G1 to S: G1 to S: Ensures that the cell’s DNA is Ensures that the cell’s DNA is suitable for replicationsuitable for replication– p53 protein expressed when DNA is p53 protein expressed when DNA is
damageddamagedInhibits replicationInhibits replicationStimulates synthesis of DNA repair Stimulates synthesis of DNA repair
enzymesenzymesTriggers cell death (apoptosis) if Triggers cell death (apoptosis) if
damage can’t be repaireddamage can’t be repaired
Chapter 11 31
Chapter 11 32
Checkpoints Control Cell CycleCheckpoints Control Cell Cycle
• G2 to mitosis:G2 to mitosis: Ensures that DNA has Ensures that DNA has been completely and accurately been completely and accurately replicatedreplicated– p53 protein expression leads to decrease p53 protein expression leads to decrease
in synthesis and activity of an enzyme in synthesis and activity of an enzyme that facilitates chromosome condensation that facilitates chromosome condensation
– chromosomes remain extended and chromosomes remain extended and accessible to DNA repair enzymes, which accessible to DNA repair enzymes, which fix DNA before cell enters mitosisfix DNA before cell enters mitosis
Chapter 11 33
Checkpoints Control Cell CycleCheckpoints Control Cell Cycle
• Metaphase to anaphase:Metaphase to anaphase: Ensures that Ensures that the chromosomes are aligned properly the chromosomes are aligned properly at the metaphase plateat the metaphase plate– a variety of proteins prevent separation of a variety of proteins prevent separation of
the sister chromatids if there are defects the sister chromatids if there are defects in chromosome alignment or spindle in chromosome alignment or spindle functionfunction
Chapter 11 34
Prevalence of Sexual ReproductionPrevalence of Sexual Reproduction
Asexual reproduction by mitosis produces Asexual reproduction by mitosis produces genetically identical offspringgenetically identical offspring
Sexual reproduction by meiosis shuffles the Sexual reproduction by meiosis shuffles the genes to produce genetically unique offspringgenes to produce genetically unique offspring
• Wide use of sexual reproduction suggests that Wide use of sexual reproduction suggests that DNA reshuffling is advantageousDNA reshuffling is advantageous
• Variation in offspring provided by sexual Variation in offspring provided by sexual reproduction confers a large evolutionary reproduction confers a large evolutionary advantageadvantage
Chapter 11 35
Genetic Variability from MutationGenetic Variability from Mutation
Mutations are the ultimate source of genetic Mutations are the ultimate source of genetic variabilityvariability
Most mutations are harmful or lethal; a few are Most mutations are harmful or lethal; a few are neutral or even beneficialneutral or even beneficial
Mutation gives rise to new Mutation gives rise to new allelesalleles Alleles are alternate gene forms that may produce Alleles are alternate gene forms that may produce
differences in structure or functiondifferences in structure or functionHomologous chromosomes carry alleles for the Homologous chromosomes carry alleles for the
same genes or characteristicssame genes or characteristics• Each chromosome may carry a different allele of a Each chromosome may carry a different allele of a
gene (e.g. for eye color)gene (e.g. for eye color)
Chapter 11 36
Chapter 11 37
Combination of Parental AllelesCombination of Parental Alleles
Combining the parental chromosomes Combining the parental chromosomes through sexual reproduction can produce through sexual reproduction can produce offspring with allelic combinations that offspring with allelic combinations that may be advantageousmay be advantageous
Sexual reproduction causes variability Sexual reproduction causes variability 1.1. Combinations of gene alleles on one Combinations of gene alleles on one
homologous chromosome are homologous chromosome are combined with combinations of gene combined with combinations of gene alleles on the other homologous alleles on the other homologous chromosomechromosome
Chapter 11 38
Combination of Parental AllelesCombination of Parental Alleles
Sexual reproduction causes variabilitySexual reproduction causes variability
2. Different homologous chromosomes with 2. Different homologous chromosomes with certain alleles are combined with other certain alleles are combined with other homologous chromosomes in a random homologous chromosomes in a random manner… manner…
3. Two gametes produced by meiosis each 3. Two gametes produced by meiosis each contribute their unique allelic combinations contribute their unique allelic combinations to produce a new offspringto produce a new offspring
Chapter 11 39
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 40
Meiosis IIMeiosis II
Prophase IIProphase II Metaphase IIMetaphase II Anaphase IIAnaphase II Telophase IITelophase IIFourFour
HaploidHaploidCellsCells
Similar to MitosisSimilar to Mitosis
Chapter 11 41
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 42 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 43 Meiosis vs. Mitosis:Meiosis vs. Mitosis:
Comparison of StagesComparison of Stages
Chapter 11 44
Novel Chromosome CombinationsNovel Chromosome Combinations
Genetic variability among organisms is Genetic variability among organisms is essential in a changing environmentessential in a changing environment
Mutations produce new variation but are Mutations produce new variation but are relatively rare occurrencesrelatively rare occurrences
Randomized line up and separation of Randomized line up and separation of homologous chromosomes in Meiotic homologous chromosomes in Meiotic Metaphase I and Anaphase I increase Metaphase I and Anaphase I increase variationvariation
• The number of possible combinations is 2The number of possible combinations is 2nn, , where n = number of homologous pairswhere n = number of homologous pairs
Chapter 11 45
Crossing OverCrossing Over
Variation also enhanced by genetic Variation also enhanced by genetic recombinationrecombination
Crossing over in Meiotic Prophase I creates Crossing over in Meiotic Prophase I creates chromosomes with new allele chromosomes with new allele combinationscombinations
Combined with homologue shuffling in Combined with homologue shuffling in Metaphase/Anaphase I, each gamete Metaphase/Anaphase I, each gamete produced in meiosis is virtually uniqueproduced in meiosis is virtually unique
Chapter 11 46
Metaphase Alignment ScenariosMetaphase Alignment Scenarios
Chapter 11 47
Fusion of GametesFusion of Gametes
Fusion of games from two individuals further Fusion of games from two individuals further increases possible 2n combinationsincreases possible 2n combinations
Gametes from two humans could produce Gametes from two humans could produce about 64 trillion different 2n combinationsabout 64 trillion different 2n combinations
Taken together with crossing over, each Taken together with crossing over, each human individual is absolutely genetically human individual is absolutely genetically uniqueunique
Chapter 11Chapter 11
The endThe end