100 µm200 µm 20 µm (a) Reproduction (b) Growth and development (c) Tissue renewal 1.
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Transcript of 100 µm200 µm 20 µm (a) Reproduction (b) Growth and development (c) Tissue renewal 1.
100 µm 200 µm 20 µm
(a) Reproduction (b) Growth and development
(c) Tissue renewal
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20 µm
2
0.5 µm Chromosomes
Chromosomeduplication(including DNAsynthesis)
Chromo-some arm
Centromere
Sisterchromatids
DNA molecules
Separation ofsister chromatids
Centromere
Sister chromatids
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G2 of Interphase
Centrosomes(with centriolepairs)
Chromatin(duplicated)
Nucleolus Nuclearenvelope
Plasmamembrane
Early mitoticspindle
Aster Centromere
Chromosome, consisting of two sister chromatids
Prophase Prometaphase
Fragmentsof nuclearenvelope
Nonkinetochoremicrotubules
Kinetochore Kinetochoremicrotubule
Metaphase
Metaphaseplate
Spindle Centrosome atone spindle pole
Anaphase
Daughterchromosomes
Telophase and Cytokinesis
Cleavagefurrow
Nucleolusforming
Nuclearenvelopeforming
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Pair of homologousreplicated chromosomes
Centromere
Sisterchromatids
Metaphasechromosome
5 µm
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Key
Maternal set ofchromosomes (n = 3)
Paternal set ofchromosomes (n = 3)
2n = 6
Centromere
Two sister chromatidsof one replicatedchromosome
Two nonsisterchromatids ina homologous pair
Pair of homologouschromosomes(one from each set)
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KeyHaploid (n)Diploid (2n)
Haploid gametes (n = 23)
Egg (n)
Sperm (n)
MEIOSIS FERTILIZATION
Ovary Testis
Diploidzygote(2n = 46)
Mitosis anddevelopment
Multicellular diploidadults (2n = 46)
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Key
Haploid (n)
Diploid (2n)
n nGametes
nn n
Mitosis
MEIOSIS FERTILIZATION
MEIOSIS
2n 2nZygote2n
Mitosis
Diploidmulticellularorganism
(a) Animals
Spores
Diploidmulticellularorganism(sporophyte)
(b) Plants and some algae
2n
Mitosis
Gametes
Mitosisn
nn
Zygote
FERTILIZATION
n
n
nMitosis
Zygote
(c) Most fungi and some protists
MEIOSIS FERTILIZATION
2n
Gametes
n
n
Mitosis
Haploid multi-cellular organism(gametophyte)
Haploid unicellular ormulticellular organism
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Interphase
Homologous pair of chromosomesin diploid parent cell
Chromosomesreplicate
Homologous pair of replicated chromosomes
Sisterchromatids Diploid cell with
replicated chromosomes
Meiosis I
Homologouschromosomesseparate
1
Haploid cells withreplicated chromosomes
Meiosis II
2 Sister chromatidsseparate
Haploid cells with unreplicated chromosomes
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Prophase I Metaphase I Anaphase ITelophase I and
CytokinesisProphase II Metaphase II Anaphase II Telophase II and
Cytokinesis
Centrosome(with centriole pair)
Sisterchromatids Chiasmata
Spindle
Homologouschromosomes
Fragmentsof nuclearenvelope
Centromere(with kinetochore)
Metaphaseplate
Microtubuleattached tokinetochore
Sister chromatidsremain attached
Homologouschromosomesseparate
Cleavagefurrow
Sister chromatidsseparate Haploid daughter cells
forming
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MITOSIS MEIOSIS
MEIOSIS I
Prophase I
Chiasma
Chromosomereplication
Homologouschromosomepair
Chromosomereplication
2n = 6
Parent cell
Prophase
Replicated chromosome
Metaphase Metaphase I
Anaphase ITelophase I
Haploid n = 3
Daughter cells ofmeiosis I
MEIOSIS II
Daughter cells of meiosis II
nnnn
2n2n
Daughter cellsof mitosis
AnaphaseTelophase
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Possibility 1 Possibility 2
Two equally probablearrangements ofchromosomes at
metaphase I
Metaphase II
Daughtercells
Combination 1 Combination 2 Combination 3 Combination 4
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Prophase Iof meiosis
Pair ofhomologs
Nonsisterchromatidsheld togetherduring synapsis
Chiasma
Centromere
Anaphase I
Anaphase II
Daughtercells
Recombinant chromosomes
TEM
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Meiosis I
Nondisjunction
(a) Nondisjunction of homologous chromosomes in meiosis I
(b) Nondisjunction of sister chromatids in meiosis II
Meiosis II
Nondisjunction
Gametes
Number of chromosomes
n + 1 n + 1 n + 1n – 1 n – 1 n – 1 n n
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