Cell cycle... Cell Reproduction
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Transcript of Cell cycle... Cell Reproduction
ASSIGNMENT # 03• Prepared by Amjad Khan• Submitted to Dear, Sir Ghadir Ali• Program BS Microbiology 3th • Subject CELL BIOLOGY• Topic CELL CYCLE• Date 12th January, 2015
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TypES of CEll TypES of CEll REpRoduCTIoNREpRoduCTIoNAsexual reproductionAsexual reproduction involves a involves a
single cellsingle cell dividing to make dividing to make 2 new, 2 new, identical daughter cellsidentical daughter cells
Mitosis & binary fission Mitosis & binary fission are are examples of asexual reproductionexamples of asexual reproduction
Sexual reproductionSexual reproduction involves two involves two cells (egg & sperm) joining to make a cells (egg & sperm) joining to make a new cell (zygote)new cell (zygote) that is that is NOT NOT identical to the original cellsidentical to the original cellsMeiosisMeiosis is an exampleis an example
Division Mechanisms
Prokaryotic organisms
– Binary fission
Eukaryotic organisms
– Mitosis• Karyokinesis (division of nucleus)
• Cytokinesis (division of cytoplasm)
– Meiosis
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Cell Division in ProkaryotesCell Division in Prokaryotes Prokaryotes such as Prokaryotes such as
bacteriabacteria divide into 2 divide into 2 identical cells by the identical cells by the process of process of binary binary fissionfission
Single chromosome Single chromosome makes a copy of makes a copy of itselfitself
Cell wall forms Cell wall forms between the between the chromosomes dividing chromosomes dividing the cellthe cell
Parent Parent cellcell
2 identical daughter cells2 identical daughter cells
Chromosome Chromosome doublesdoubles
Cell splitsCell splits
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Five Phases of the Cell CycleFive Phases of the Cell Cycle
GG11 - primary growth/gap phase - primary growth/gap phaseS – synthesis; DNA replicatedS – synthesis; DNA replicatedGG22 - secondary growth/gap - secondary growth/gap phase phase collectively these 3 stages are collectively these 3 stages are called called interphaseinterphase
M - mitosisM - mitosisC - cytokinesisC - cytokinesis
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Interphase - GInterphase - G11 Stage Stage
11stst growth/gap stage growth/gap stage after cell after cell divisiondivision
Cells Cells maturemature by making more by making more cytoplasm & organellescytoplasm & organelles
Cell carries on its Cell carries on its normal normal metabolic activities metabolic activities i.e. i.e. respiration, digestion etc.respiration, digestion etc.
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Interphase – S StageInterphase – S StageSynthesisSynthesis stage stageDNADNA is copied or is copied or replicatedreplicated
Two Two identical identical copies copies of DNAof DNA
Original Original DNADNA
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Interphase – GInterphase – G22 Stage Stage22ndnd Growth/Gap Growth/Gap Stage StageOccurs Occurs after DNA has been copie; after DNA has been copie; also in preparation for M phasealso in preparation for M phase
All cell All cell structures needed for structures needed for divisiondivision are made (e.g. centrioles) are made (e.g. centrioles)
Both Both organelles & proteinsorganelles & proteins are are synthesizedsynthesized
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What’s Happening in Interphase?What’s Happening in Interphase?
What the cell looks likeWhat the cell looks like
Animal Cell
What’s occurring
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Sketch the Cell CycleSketch the Cell Cycle
Daughter Daughter CellsCells
DNA CopiedDNA Copied
Cells Cells MatureMature
Cells prepare for Cells prepare for DivisionDivision
Cell Divides into Cell Divides into Identical cellsIdentical cells
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MitosisMitosisDivision of the Division of the
nucleus nucleus (karyokinesis)(karyokinesis)
Division of the Division of the cytoplasm cytoplasm (cytokinesis)(cytokinesis)
Only occurs in Only occurs in eukaryoteseukaryotes
Has Has fourfour stages stagesDoesn’t occur in Doesn’t occur in
some cells such as some cells such as brain cellsbrain cells
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Four Mitotic StagesFour Mitotic Stages
ProProphasephaseMetaMetaphasephaseAnaAnaphasephaseTeloTelophasephase
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Early ProphaseEarly ProphaseChromatinChromatin in nucleus condenses to in nucleus condenses to form form visible chromosomesvisible chromosomes
Mitotic spindle Mitotic spindle forms from fibers in forms from fibers in cytoskeleton or cytoskeleton or centrioles (animal)centrioles (animal)
ChromosomesChromosomes
NucleolusNucleolus CytoplasmCytoplasm
Nuclear MembraneNuclear Membrane
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Late ProphaseLate ProphaseNuclear membrane & nucleolusNuclear membrane & nucleolus are are broken downbroken down
ChromosomesChromosomes continue condensing & continue condensing & are are clearly visibleclearly visible
Spindle fibers called Spindle fibers called kinetochoreskinetochores attach to the centromereattach to the centromere of each of each chromosomechromosome
SpindleSpindle finishes forming between the finishes forming between the poles of the cellpoles of the cell
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Late ProphaseLate Prophase
Nucleus & Nucleolus have disintegratedNucleus & Nucleolus have disintegrated
Chromosomes Chromosomes
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Spindle Fiber attached to Spindle Fiber attached to ChromosomeChromosome
Kinetochore FiberKinetochore Fiber
ChromosomeChromosome
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Review of ProphaseReview of Prophase
What the cell What the cell looks likelooks like
What’s happeningWhat’s happening
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Spindle FibersSpindle FibersThe mitotic The mitotic spindlespindle form from the form from the microtubulesmicrotubules in plantsin plants and and centrioles centrioles in animal cellsin animal cells
Polar fibers Polar fibers extend from one pole of extend from one pole of the cell to the opposite polethe cell to the opposite pole
Kinetochore fibersKinetochore fibers extend from the extend from the pole to the centromere of the pole to the centromere of the chromosome to which they attachchromosome to which they attach
AstersAsters are short fibers radiating are short fibers radiating from centriolesfrom centrioles
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MetaphaseMetaphaseChromosomes, attached to the Chromosomes, attached to the kinetochore fiberskinetochore fibers, move to the center , move to the center of the cellof the cell
Chromosomes are now lined up at the Chromosomes are now lined up at the equatorequator
Pole of Pole of the Cellthe Cell
Equator of CellEquator of Cell
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Review of MetaphaseReview of Metaphase
What the cell looks What the cell looks likelike
What’s What’s occurringoccurring
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AnaphaseAnaphaseOccurs Occurs rapidlyrapidlySister Sister chromatidschromatids are are pulled apart to pulled apart to opposite polesopposite poles of the cell by of the cell by kinetochore kinetochore fibersfibers
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Anaphase ReviewAnaphase Review
What the What the cell looks cell looks
likelike
What’s What’s occurringoccurring
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TelophaseTelophaseSister chromatids at Sister chromatids at opposite opposite polespoles
Spindle Spindle disassemblesdisassemblesNuclear envelopeNuclear envelope forms around forms around each set of sister chromatidseach set of sister chromatids
NucleolusNucleolus reappears reappearsCYTOKINESISCYTOKINESIS occurs occursChromosomes reappear as Chromosomes reappear as chromatinchromatin
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CytokinesisCytokinesisMeans division of the cytoplasmMeans division of the cytoplasmDivisionDivision of cell into two, of cell into two, identical halves called identical halves called daughter daughter cellscells
In plant cells, cell plate In plant cells, cell plate forms forms at the equator to divide cellat the equator to divide cell
In animal cells, In animal cells, cleavage furrow cleavage furrow forms to split cellforms to split cell
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CytokinesisCytokinesis
Cleavage furrow Cleavage furrow in animal cellin animal cell
Cell plate in Cell plate in animal cellanimal cell
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Daughter Cells of MitosisDaughter Cells of MitosisHave the Have the same number of same number of chromosomes as each otherchromosomes as each other and as and as the parent cellthe parent cell from which they from which they were formedwere formed
IdenticalIdentical to each other, but to each other, but smaller smaller than parent cellthan parent cell
Must Must grow in sizegrow in size to become mature to become mature cells cells (G(G11 of Interphase) of Interphase)
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Identical Daughter CellsIdentical Daughter Cells
Chromosome number the Chromosome number the samesame, but cells , but cells smallersmaller than parent cell than parent cell
What is What is the 2n the 2n
or or diploid diploid
number?number?
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InterphaseInterphase
ProphaseProphase
MetaphaseMetaphaseAnaphaseAnaphase
TelophaseTelophase
Name the Mitotic Stages:Name the Mitotic Stages:
Name this?Name this?
Name this?Name this?
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Eukaryotic Cell DivisionEukaryotic Cell Division
Used for Used for growth and growth and repairrepair
Produce two new cells Produce two new cells identical to the original identical to the original cellcell
Cells are Cells are diploid (2n)diploid (2n)Chromosomes during Chromosomes during Metaphase of mitosisMetaphase of mitosis
ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophaseCytokinesisCytokinesis
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Mitosis AnimationMitosis AnimationName each stage as you see it occur?Name each stage as you see it occur?
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Mitosis in Onion Root TipsMitosis in Onion Root TipsDo you see any stages of mitosis?Do you see any stages of mitosis?
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Locate the Four Mitotic Locate the Four Mitotic Stages in PlantsStages in Plants
MetaphaseMetaphase
ProphaseProphase
AnaphaseAnaphase
TelophaseTelophase
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Uncontrolled Mitosis If mitosis is not If mitosis is not
controlledcontrolled, unlimited , unlimited cell division occurs cell division occurs causing cancerous causing cancerous tumorstumors
OncogenesOncogenes are special are special proteins proteins that increase the chance increase the chance that a normal cell that a normal cell develops into adevelops into a tumor tumor cell cell
Cancer cellsCancer cells
Words to knoWGametes - reproductive cells that unite during sexual
reproduction to form a new cell called a zygote (male = sperm, female = egg cell)
Germ cells – sperm or egg cells
Somatic cells - any cell other than the reproductive cells
Diploid - a cell that contains two sets of chromosomes (2n), as normally found in somatic cells
Haploid - have one set of chromosomes (n=1) as in germ cells, or half as many as a somatic cell
Homologous – chromosomes that are alike in structure and genes
Alleles – different forms of a gene ex. if talking about hair color as the gene, different alleles would be different colors like red, blonde, black etc. 50
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Facts About MeiosisFacts About MeiosisPreceded by interphase which Preceded by interphase which includesincludes chromosome replicationchromosome replication
TwoTwo meiotic divisions: meiotic divisions: Meiosis I Meiosis I and Meiosis IIand Meiosis II
AkaAka reduction-divisionreduction-divisionOriginal cell is diploid (2n)Original cell is diploid (2n)Four daughter cellsFour daughter cells produced that produced that are are haploid (n)haploid (n)
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Facts About MeiosisFacts About MeiosisDaughter cellsDaughter cells contain half the number contain half the number
of chromosomesof chromosomes as the original cellas the original cellProducesProduces gametesgametes (eggs & sperm(eggs & sperm))Occurs in the Occurs in the testestestes in males in males
((SpermatogenesisSpermatogenesis))Occurs in the Occurs in the ovariesovaries in females in females
((OogenesisOogenesis))Human diploid cells have Human diploid cells have 46 chromosomes 46 chromosomes
(2n=46)(2n=46)Human sperm and egg cells have Human sperm and egg cells have 23 23
chromosomes (n=23) eachchromosomes (n=23) each
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Start with Start with 46 double stranded 46 double stranded chromosomes (2n)chromosomes (2n)After 1 division - After 1 division - 23 double 23 double stranded chromosomes (n)stranded chromosomes (n)After 2nd division - After 2nd division - 23 single 23 single stranded chromosomes (n)stranded chromosomes (n) Occurs in our Occurs in our germ cellsgerm cells
More Meiosis FactsMore Meiosis Facts
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Why Do we Need Meiosis?Why Do we Need Meiosis?It is the fundamental basis of It is the fundamental basis of sexual reproductionsexual reproduction
Two haploid (1n) gametes are Two haploid (1n) gametes are brought together through brought together through fertilizationfertilization to form a diploid to form a diploid (2n) zygote(2n) zygote
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Fertilization – “Putting it Fertilization – “Putting it all together”all together”
1n =31n =3
2n = 62n = 6
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Replication of ChromosomesReplication of ChromosomesReplicationReplication is the is the
process of process of duplicating a duplicating a chromosomechromosome
Occurs Occurs prior to prior to divisiondivision
Replicated copies Replicated copies are called are called sister sister chromatidschromatids
Held together at Held together at centromerecentromere
Occurs in Occurs in InterphaseInterphase
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A Replicated ChromosomeA Replicated Chromosome
HomologuesHomologues (same genes, (same genes, different alleles)different alleles)
SisterSisterChromatidsChromatids(same genes,(same genes,same alleles)same alleles)
Gene XGene X
Homologues separate in meiosis I and Homologues separate in meiosis I and therefore different alleles separate.therefore different alleles separate.
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Meiosis Forms Haploid GametesMeiosis Forms Haploid GametesMeiosis must Meiosis must reduce the chromosome number reduce the chromosome number
by halfby half Fertilization then restoresFertilization then restores the 2n number the 2n number
from mom from dad child
meiosis reducesgenetic content
toomuch!
The right number!
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Meiosis: Two Part Cell Meiosis: Two Part Cell DivisionDivision
HomologuesHomologuesseparateseparate
Sister Sister chromatidschromatidsseparateseparate
DiploidDiploid
MeiosisMeiosis I I
MeiosisMeiosisIIII
DiploidDiploid
HaploidHaploid
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Meiosis I: Reduction DivisionMeiosis I: Reduction Division
NucleusNucleus SpindleSpindlefibersfibers NuclearNuclear
envelopeenvelopeEarly Early Prophase IProphase I
(Chromosome (Chromosome number number doubleddoubled))
Late Late Prophase Prophase
II
Metaphase Metaphase II Anaphase Anaphase
IITelophase I Telophase I
(diploid)(diploid)
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Prophase IProphase I
Early prophaseEarly prophaseHomologues Homologues pair.pair.Crossing over Crossing over occursoccurs.
Late prophaseLate prophaseChromosomes condense.Chromosomes condense.Spindle forms.Spindle forms.Nuclear envelope Nuclear envelope fragments.fragments.
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Tetrads Form in Prophase ITetrads Form in Prophase I
Homologous chromosomesHomologous chromosomes(each with sister chromatids) (each with sister chromatids)
Join to form aJoin to form a TETRADTETRAD
Called SynapsisCalled Synapsis
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Crossing-OverCrossing-Over Homologous Homologous
chromosomeschromosomes in a in a tetrad tetrad cross over cross over each othereach other
Pieces of Pieces of chromosomes or chromosomes or genes are genes are exchangedexchanged
Produces Produces Genetic Genetic recombinationrecombination in in the offspringthe offspring
•Occurs in nonsister chromatids•Increases genetic variability
Genetic recombination in which a strand of the genetic material (DNA/RNA)is broken and then joined to the end of a different DNA molecule.
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Crossing-over multiplies the already huge Crossing-over multiplies the already huge number of different gamete types number of different gamete types
produced by independent assortmentproduced by independent assortment
Crossing-OverCrossing-Over
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Metaphase IMetaphase I
Homologous pairsHomologous pairs of chromosomes of chromosomes align along the align along the equatorequator of the of the
cellcell
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Anaphase IAnaphase I
Homologues separateHomologues separate and and move to opposite poles.move to opposite poles.
Sister chromatids Sister chromatids remain remain attached attached at theirat their centromerescentromeres.
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Telophase ITelophase I
Nuclear envelopes Nuclear envelopes reassemble.reassemble.
Spindle disappears.Spindle disappears.
Cytokinesis Cytokinesis divides cell divides cell into two.into two.
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Meiosis IIMeiosis IIOnly one homologue of each Only one homologue of each
chromosome is present in chromosome is present in the cellthe cell.
Meiosis II produces gametes with Meiosis II produces gametes with one copy of each chromosome and one copy of each chromosome and thus one copy of each gene.thus one copy of each gene.
Sister chromatids carry Sister chromatids carry identical genetic identical genetic informationinformation. .
Gene XGene X
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Meiosis II: Reducing Meiosis II: Reducing Chromosome NumberChromosome Number
Prophase Prophase IIII
Metaphase Metaphase IIII
Anaphase Anaphase IIII
Telophase Telophase IIII 4 Identical 4 Identical
haploid cellshaploid cells
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Prophase IIProphase II
Nuclear envelope Nuclear envelope fragments.fragments.
Spindle forms.Spindle forms.
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Metaphase IIMetaphase II
Chromosomes align Chromosomes align along along equatorequator of cell of cell..
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Anaphase IIAnaphase II
Sister chromatidsSister chromatids separate and separate and move to move to opposite opposite polespoles.
EquatorEquator
PolePole
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Telophase IITelophase II
Nuclear envelope Nuclear envelope assembles.assembles.
Chromosomes Chromosomes decondense.decondense.
Spindle disappears.Spindle disappears.
Cytokinesis divides Cytokinesis divides cell into two.cell into two.
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Results of MeiosisResults of MeiosisGametes (egg & sperm) Gametes (egg & sperm) formform
Four haploid cells with Four haploid cells with one copy of each one copy of each chromosome chromosome
One allele of each geneOne allele of each gene
Different combinations of Different combinations of alleles for different alleles for different genes along the genes along the chromosomechromosome
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SpermatogenesisSpermatogenesisOccurs in the Occurs in the
testestestesTwo divisions Two divisions
produce 4 produce 4 spermatidsspermatids
Spermatids Spermatids mature mature into sperminto sperm
Men produce about Men produce about 250,000,000 250,000,000 sperm per daysperm per day
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OogenesisOogenesisOccurs in the Occurs in the ovariesovariesTwo divisions produce Two divisions produce 3 polar bodies3 polar bodies that die and that die and 1 egg1 egg
Polar bodies die because of Polar bodies die because of unequal unequal division of cytoplasmdivision of cytoplasm
Immature egg called Immature egg called oocyteoocyteStarting at puberty, one oocyte Starting at puberty, one oocyte matures into an matures into an ovum (egg)ovum (egg) every 28 every 28 daysdays
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OogenesisOogenesis
OogoniumOogonium(diploid)(diploid)
MitosisMitosis
PrimaryPrimaryoocyteoocyte(diploid)(diploid)
Meiosis IMeiosis I
SecondarySecondaryoocyteoocyte(haploid)(haploid)
Meiosis IIMeiosis II(if fertilization(if fertilizationoccurs)occurs)
First polar bodyFirst polar bodymay divide may divide (haploid)(haploid) PolarPolar
bodiesbodiesdiedie
Ovum (egg)Ovum (egg)
SecondSecondpolar bodypolar body(haploid)(haploid)
a
A
X
X
a
X
A X
a
X
a
X
MatureMatureeggegg
A
X
A
X
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MitosisMitosis MeiosisMeiosisNumber of Number of
divisionsdivisions11 22
Number of Number of daughter cellsdaughter cells 22 44
Genetically Genetically identical?identical?
YesYes NoNo
Chromosome #Chromosome # Same as parentSame as parent Half of parentHalf of parent
WhereWhere Somatic cellsSomatic cells Reproductive cellsReproductive cells
WhenWhen Throughout lifeThroughout life At sexual maturityAt sexual maturity
RoleRole Growth and Growth and repairrepair
Sexual reproductionSexual reproduction
Comparison of DivisionsComparison of Divisions
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Meiosis Mitosis
Definition:
A type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes in a diploid cell.
A process of asexual reproduction in which the cell divides in two producing a replica, with an equal number of chromosomes in haploid cell
Function: sexual reproduction Cellular Reproduction & general growth and repair of the body
Type of Reproduction: Sexual AsexualOccurs in: Humans, animals, plants, fungi all organismsGenetically: different identical
Crossing Over: Yes, mixing of chromosomes can occur. No, crossing over cannot occur.
Pairing of Homologues: Yes NoNumber of Divisions: 2 1Number of Haploid Daughter Cells produced:
4 2
Chromosome Number: Reduced by half Remains the same
Steps:
The steps of meiosis are Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II.
The steps of mitosis are Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis
Karyokenesis: Occurs in Interphase I Occurs in Interphase
Cytokenesis: Occurs in Telophase I & Telohpase II Occurs in Telophase
Centromeres Split:The centromeres do not separate during anaphase I, but during anaphase II
The centromeres split during Anaphase
Creates: Sex cells only: Female egg cells or Male sperm cells
Makes everything other than sex cells