Post on 13-Jan-2016
PRODUCTION OF GAMETES
MEIOSISMEIOSIS
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http://www.khanacademy.org/video/phases-of-meiosis?
playlist=Biology
KHAN ACADEMY LINK TO MEIOSIS
Click on link to watch Mr. Anderson talk about meiosis
• http://www.safeshare.tv/w/OALswNWWbc
ASEXUAL REPRODUCTION Bacteria and Amoeba reproduce
using ___________________________
BINARY FISSION
BACTERIAAmoeba
ASEXUAL REPRODUCTION
HYDRA PLANARIA
BUDDING & REGENERATION are used by organisms to reproduce asexually by MITOSIS
BINARY FISSION & MITOSIS Produces cells that are __________copies of parent cellIDENTICAL
HumanSomatic (body) cell
Diploid (2n)
2n=46
2n=46
2n=46
MITOSIS Makes ___ cells genetically _________ to parent cell & to each other Makes ___ cells Makes _______________ Used by organisms to: increase size of organism, repair injuries, replace worn out cells
2IDENTICAL
2n SOMATIC (body)
ADVANTAGES OF ASEXUAL REPRODUCTION
• Can make offspring at a faster rate: some bacteria can reproduce every 20 minutes
• Don’t need a partner
DISVANTAGES OF ASEXUAL
REPRODUCTION• ALL ALIKE
• Species CAN’T change and adapt
• One disease can wipe out whole population
SEXUAL REPRODUCTION
Combines genetic material
from 2 parents (sperm & egg)
so offspring aregenetically __________ from parents
DIFFERENT
ADVANTAGES OF SEXUAL REPRODUCTION
Allows for variation in population
Individuals can be different
Provides foundation for EVOLUTION: genetic diversity
Allow species adapt to changes intheir environment
MEIOSIS is the way…
to make cells with ½ the number of chromosomesfor sexual reproduction
CHARACTERISTICS OF LIVING THINGS ALL LIVING THINGS ______________
REPRODUCE
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MEIOSIS
• Occurs only in ______________ (testes or ovaries)
• Male: _____________________
• Female: ___________________
GONADS
SPERMATOGENESIS
OOGENESIS
MAKING SPERM & EGGS
___________________= MAKING MATURE SPERM
Mature & grow flagella
SPERMATOGENESIS
Replication(interphase)
Meiosis I
Meiosis II
SPERMSPERMATOGENESISSPERMATOGENESIS
POLAR BODIES
Produces: 1 “good” egg
3
CYTOPLASM DIVIDES UNEVENLY
__________________ = MAKING a MATURE EGG
OOGENESIS
Life History of OVUM(EGG)• as a fetus, oogonia divide to produce millions
by mitosis but most degenerate
• Some develop into primary oocytes & stop in prophase stage of meiosis I– 200,000 to 2 million present at birth– 40,000 remain at puberty but only 400
mature during a woman’s life
• Each month, hormones cause meiosis I to resume in several follicles so that metaphase II is reached by ovulation
• Penetration by the sperm causes the final stages of meiosis to occur
Sperm donates DNA
WHY MAKE ONLY ONE “GOOD” EGG?
Most of the cell parts and nutrients needed for baby come from EGG!
“Self digest”
Using ______________
POLAR BODIES DEGENERATE (DIE)
LYSOSOMES
= __________________ “cell suicide” for good of organism
APOPTOSIS
OVUM (EGG)
Replication(interphase
Meiosis I
Meiosis II
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FERTILIZATION• The fusion of a spermsperm and eggegg to form a
ZYGOTEZYGOTE.• A ZYGOTE is a fertilized egg
n=23egg
sperm n=23
2n=46zygote
Sperm provides DNA
All the starting nutrients, organelles, molecule building blocks, etc. have to come from the egg.
OVUM
SPERM
COMPARISON OF
OOGENESIS & SPERMATOGENESIS
DIPLOID & HAPLOID Most cells have 2 copies of each chromosome = _____ or_________
(one from mom; one from dad)
All BODY (___________) cells are diploid
DIPLOID2n
HOMOLOGOUSCHROMOSOMES
SOMATIC
http://www.biostudio.com/d_%20Replication%20of%20a%20Chromosome.htm
WATCH AN ANIMATION OF HOW A CHROMOSOME IS REPLICATED
DIPLOID & HAPLOID
Sex cells or Gametes have only
one copy of each chromosome =
_____or __________ All sperm and egg cells are haploid
HAPLOID1n
MEIOSIS• Makes ____ cells
genetically different from parent cell & from each other
• Makes _____ cells• Makes ______________
• Used for ____________
4
1n
GAMETES (sperm & eggs)
sexual reproduction
MEIOSIS
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INTERPHASE IINTERPHASE I
• Similar to mitosismitosis interphase• CHROMOSOMESCHROMOSOMES REPLICATE (S phase) (S phase) • Each duplicated chromosomechromosome consist of
TWO IDENTICAL SISTER CHROMATIDSCHROMATIDS attached at their centromerescentromeres
• CENTRIOLECENTRIOLE PAIRS also replicate.
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Interphase I
• NUCLEUSNUCLEUS AND NUCLEOLUSNUCLEOLUS visible.
Nuclear membrane
Nucleolus
Cell membrane
Chromatin
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MEIOSIS IMEIOSIS I
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Stages of Meiosis IStages of Meiosis I
• Cell division Cell division that reduces the chromosomechromosome number by one-one-halfhalf
• FourFour phases phases:a.a. Prophase IProphase Ib.b. Metaphase IMetaphase Ic.c. Anaphase IAnaphase Id.d. Telophase ITelophase I
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Prophase IProphase I• Longest and most complexLongest and most complex phase phase
(90%)(90%)• ChromosomesChromosomes condense• SynapsisSynapsis occurs: homologous homologous
chromosomes chromosomes come together to form a tetradtetrad
• TetradTetrad is two chromosomeschromosomes or four chromatidschromatids (sister and nonsister chromatids)
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Prophase IProphase I - - SynapsisSynapsis
Homologous chromosomes
Sister chromatids Sister chromatidsTetrad
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Homologous ChromosomesHomologous Chromosomes
• Pair of chromosomeschromosomes (maternalmaternal and paternalpaternal) that are similar in shape and size
• Homologous pairs (tetrads)(tetrads) carry genes controlling the same inherited traits
• Each locuslocus (position of a gene)(position of a gene) is in the same position on homologues
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Homologous ChromosomesHomologous Chromosomes
Paternal Maternal
eye color locus
eye color locus
hair color locus
hair color locus
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Crossing OverCrossing Over
• Crossing overCrossing over (variation) (variation) may occur between nonsister chromatidschromatids at the chiasmatachiasmata
• Crossing overCrossing over: segments of nonsister chromatidschromatids break and reattach to the other chromatidchromatid
• Chiasmata (chiasma) Chiasmata (chiasma) are the sites of crossing overcrossing over
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Prophase IProphase I
CentriolesSpindle fiber
Asterfibers
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Metaphase IMetaphase I
• ShortestShortest phase phase• TetradsTetrads align on the metaphase metaphase
plateplate• Independent assortment occursIndependent assortment occurs• Chromosomes separate randomlyChromosomes separate randomly
to the poles of the cellsto the poles of the cells
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Metaphase IMetaphase I• Independent assortment causes
variation in the forming cells• Orientation of homologous pair to
poles is random• Formula for determining variation: Formula: 2n
ExampleExample: 2n = 4: 2n = 4 then n = 2then n = 2
thus 2thus 22 2 = 4 combinations= 4 combinations
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Metaphase IMetaphase I
Metaphase plate
OR
Metaphase plate
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Question:Question:
• In terms of Independent In terms of Independent Assortment, Assortment, how many different how many different combinations of sperm could a combinations of sperm could a human male produce? human male produce?
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AnswerAnswer
• Formula: 2Formula: 2nn
• Human chromosomes:Human chromosomes: 2n = 462n = 46 n = 23n = 23 222323 = ~8 million combinations = ~8 million combinations
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Anaphase IAnaphase I
• Homologous chromosomes Homologous chromosomes separate and move towards the poles
• Sister chromatids Sister chromatids remain attached at their centromerescentromeres
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Anaphase IAnaphase I
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Telophase ITelophase I
• Each pole now has haploidhaploid set of chromosomeschromosomes
• 1n = 23 (human)1n = 23 (human)• CytokinesisCytokinesis occurs and two
haploid daughter cells are formed
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Telophase ITelophase I
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MEIOSIS IIMEIOSIS II
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Meiosis IIMeiosis II
• Short or NoShort or No interphase II interphase II • DNA NOT replicatedDNA NOT replicated again again• Remember: Meiosis II Remember: Meiosis II is similar
to mitosismitosis• Prophase I, Metaphase II, Prophase I, Metaphase II,
Anaphase II, and Telophase IIAnaphase II, and Telophase II
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Prophase IIProphase II• Same as prophaseprophase in mitosismitosis• Nuclear envelope breaks down and the Nuclear envelope breaks down and the
spindle apparatus formsspindle apparatus forms
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Metaphase IIMetaphase II• Same as metaphasemetaphase in mitosismitosis• Chromatids lined up at equatorChromatids lined up at equator
Metaphase plateMetaphase plate
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Anaphase IIAnaphase II
• Same as anaphaseanaphase in mitosismitosis• Sister chromatids separateSister chromatids separate
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Telophase IITelophase II
• Same as telophasetelophase in mitosismitosis• Nuclei reform• CytokinesisCytokinesis occurs• Remember: Remember: Four haploid Four haploid
daughter cellsdaughter cells produced produced• GametesGametes = sperm or egg = sperm or egg
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Telophase IITelophase II
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Genetic VariationGenetic Variation
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Variation
• Important to the survival of Important to the survival of populationspopulations
• Aids in natural selectionAids in natural selection• Strongest individuals are able Strongest individuals are able
to survive and reproduceto survive and reproduce
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QuestionQuestion• What are the three sources of What are the three sources of
genetic variation in sexual genetic variation in sexual reproduction?reproduction?
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Answer:Answer:
1.1. Crossing OverCrossing Over (Prophase I)(Prophase I)
2. 2. Independent AssortmentIndependent Assortment (Metaphase I)(Metaphase I)
3. 3. Random FertilizationRandom Fertilization(sperm joins with egg)(sperm joins with egg)
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Remember: Variation is helpful to the
survival of a species!
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Question:Question:
• A diploid cell containing 20 20 chromosomeschromosomes (2n = 20)(2n = 20) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomeschromosomes?
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Answer:Answer:
• 10 chromosomes (haploid)10 chromosomes (haploid)• 1n = 101n = 10
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Question:Question:
• A cell containing 40 CHROMOSOMES 40 CHROMOSOMES at the beginning of meiosis would, at its completion, produce how many cells and how many chromosomes in each cellchromosomes in each cell?
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ANSWER:ANSWER:
• FOUR CELLS with 20 FOUR CELLS with 20 chromosomes eachchromosomes each
Chromosome Numbers of Some Common OrganismsORGANISM BODY CELL
(2n) DIPLOIDGAMETES
(n) HAPLOID
HUMAN 46 23
GARDEN PEA 14 7
FRUIT FLY 8 4
TOMATO 24 12
DOG 78 39
CHIMPANZEE 48 24
LEOPARD FROG 26 13
CORN 20 10
MICROSCOPIC ROUNDWORM 12 6
CHICKEN 78 39
ANT 2 1
HOUSE MOUSE 40 20
CRAYFISH 200 100
RABBIT 44 22
DEER 68 34
ADDERS-TONGUE FERN (PLANT) 1200 600HORSE 64 32
EARTHWORM 36 18
DOVE 78 39
DOLPHIN 44 22
MEIOSIS I
Section 11-4
Figure 11-15 Meiosis
Section 11-4
Figure 11-15 Meiosis
MEIOSIS I
Meiosis I
Section 11-4
Figure 11-15 Meiosis
MEIOSIS I
Section 11-4
Figure 11-15 Meiosis
MEIOSIS I
Section 11-4
Figure 11-15 Meiosis
MEIOSIS I
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Figure 11-17 Meiosis IISection 11-4
Meiosis II
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Section 11-4
Figure 11-17 Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Section 11-4
Figure 11-17 Meiosis II
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Section 11-4
Figure 11-17 Meiosis II
Meiosis II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Section 11-4
Figure 11-17 Meiosis II
Meiosis II
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REVIEWREVIEW
WHAT MAKES MEIOSIS DIFFERENT FROM MITOSIS?
1. SYNAPSIS & CROSSING OVER (PROPHASE I)
2. SEGREGATION & INDEPENDENT ASSORTMENT
(ANAPHASE I)
3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT…
ONLY COPIES DNA ONCE
WHAT MAKES MEIOSIS DIFFERENT ?
1. Homologous chromosomes pair up during ________________
= ______________SYNAPSIS
This group of FOUR (4)chromatids is called a_________________TETRAD
PROPHASE I
WHAT MAKES MEIOSIS DIFFERENT?
1. Exchange of DNA betweenhomologous pairs = _____________during PROPHASE I
CROSSING OVER
Allows shuffling of genetic material=
________________
GENETIC VARIAION
http://www.biostudio.com/d_%20Meiotic%20Recombination%20Between%20Linked%20Genes.htm
CLICK ON LINK BELOW TO WATCH A CROSSING OVER ANIMATION
HOMOLOGOUS CHROMOSOMES
• SAME SIZE• SAME SHAPE• CARRY GENES for the
SAME TRAITS• BUT ______________!NOT IDENTICAL
CROSSING
OVER
• Allows for_________________in different combinations
• After crossing over, chromatid arms are________________ anymore
Image modified by Riedell
http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
rearranging of DNA
NOT IDENTICAL
WHAT MAKES MEIOSIS DIFFERENT ?
2.Separation during ANAPHASE I
INDEPENDENT ASSORTMENT
Separates gene choices and allows shuffling of genetic material or genetic diversity
SEGREGATION &
SEGREGATION(Anaphase I)
SEGREGATION & CROSSING OVER together make even more combinations
INDEPENDENT ASSORTMENT
INDEPENDENT ASSORTMENTat ANAPHASE I
Lots of different combinations are possible!
This is why you don’t look exactly like your brothers and sisters even though you share the same parents!
WHAT MAKES MEIOSIS DIFFERENT ?
Crossing over Segregation Independent assortment
are ALL ways MEIOSIS results in =______________________________
So daughter cells are ______________ from parents and from each
other
DIFFERENT
GENETIC RECOMBINATION
WHAT MAKES MEIOSIS DIFFERENT ?
3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE
G1 G2S P M A T C
G1
MITOSIS:
MEIOSIS:
S G2 P M A T CP M A T C
( I )
( II )
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REVIEW: COMPARING MITOSIS AND
MEIOSIS
MITOSIS vs MEIOSIS INTERPHASE INTERPHASE I
• DNA is spread out as chromatin• Nuclear membrane/
nucleolus visible• DNA is copied during S phase• Makes everything new cell
needs in G2
SAME AS MITOSIS
MITOSIS vs MEIOSIS PROPHASE PROPHASE I
DNA shortens and thickens into chromosomes
Nuclear membrane/ nucleolus disassembleCentrioles/
spindle fibers appear
SAME AS MITOSIS EXCEPT:
Homologous pairs match up
MITOSIS vs MEIOSIS METAPHASE METAPHASE I
• Chromosomes line up in middle(no homologs) with homologous partner
SAME AS MITOSIS EXCEPT:
MITOSIS vs MEIOSIS ANAPHASE ANAPHASE I
Chromatids splitAPART
Chromatids stay togetherHomologous pairs split
MITOSIS vs MEIOSIS TELOPHASE TELOPHASE I
See TWO nucleiNuclear membrane/ nucleolus reassembleDNA spreads out as chromatinSpindle/centrioles
disassemble
SAME AS MITOSIS
MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS I
Cytoplasm splits into 2 cells
SAME AS MITOSIS
MITOSIS vs MEIOSIS INTERPHASE II
• DNA is spread out as chromatin
• Nuclear membrane/ nucleolus visible
• DNA is copied during S phase
SKIP INTERPHASE IIDNA NOT COPIED
MITOSIS vs MEIOSIS PROPHASE PROPHASE II
• DNA scrunches into chromosomes
• Nuclear membrane/nucleolus disassemble
• Centrioles/ spindle fibers appear
SAME AS MITOSIS
MITOSIS vs MEIOSIS METAPHASE METAPHASE II
• Chromosomes line up in middle
SAME AS MITOSIS
MITOSIS vs MEIOSIS ANAPHASE ANAPHASE II
Chromatids split and move apart
SAME AS MITOSIS
MITOSIS vs MEIOSIS TELOPHASE TELOPHASE II
Two nucleiNuclear membrane/
nucleolus reassembleCentrioles/spindle fibers
disassembleDNA spreads out as chromatin
SAME AS MITOSIS
MITOSIS vs MEIOSISCYTOKINESIS CYTOKINESIS II
Cytoplasm splits SAME AS MITOSIS
Ways Meiosis is different?• Homologous pairs match up & trade DNA
(SYNAPSIS & CROSSING OVER) in PROPHASE I
•SEGREGATION
& INDEPENDENT ASSORTMENT in Anaphase I
create genetic recombination
• Skipping INTERPHASE II- (Dividing TWICE but copying DNA once)
produces 1n HAPLOID cells
CLICK TO WATCH ANIMATIONS OF MEIOSIS
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio19.swf::Stages%20of%20Meiosis
http://www.sumanasinc.com/webcontent/animations/content/meiosis.html
Centrosomes(with centriole pairs)
Sisterchromatids
Chiasmata
spindle
Tetrad
Nuclearenvelope
Chromatin
Centromere(with kinetochore)
Microtubuleattached tokinetochore
Tetads line up
Metaphaseplate
Homologouschromosomesseparate
Sister chromatidsremain attached
Pairs of homologouschromosomes split upChromosomes duplicate
Homologous chromosomes(red and blue) pair and exchangesegments; 2n = 6 in this example
INTERPHASE MEIOSIS I: Separates homologous chromosomes
PROPHASE I METAPHASE I ANAPHASE I
• Interphase and meiosis I
1
23
45
6
7
89
10
11
12
TELOPHASE I ANDCYTOKINESIS
PROPHASE II METAPHASE II ANAPHASE II TELOPHASE II ANDCYTOKINESIS
MEIOSIS II: Separates sister chromatids
Cleavagefurrow Sister chromatids
separate
Haploid daughter cellsforming
During another round of cell division, the sister chromatids finally separate;four haploid daughter cells result, containing single chromosomes
Two haploid cellsform; chromosomesare still double
Telophase I, cytokinesis, and meiosis II
1 2 3
CLICK ON THE LINK TO WATCH AN ANIMATION OF THE
COMPARISON OF MEIOSIS AND MITOSIS
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio17.swf::Comparison%20of%20Meiosis%20and%20Mitosis
When does it occur? When does it occur?
One or Two? One or Two?
Occurs or not?If yes when? Occurs or not?
If yes when?
One or two?Diploid or Haploid?
One or two?Diploid or Haploid?
What is purpose of Mitosis?
What is purpose of Mitosis?
diploid
diploid
haploid