meiosis. fig. 13-3b technique pair of homologous replicated chromosomes centromere sister chromatids...
TRANSCRIPT
MeiosisMeiosis
Fig. 13-3bFig. 13-3b
TECHNIQUE
Pair of homologousreplicated chromosomes
Centromere
Sisterchromatids
Metaphasechromosome
5 µm
Fig. 13-6Fig. 13-6
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
Key
Haploid (n)
Diploid (2n)
n n
n
nn
2n2n
Mitosis
Mitosis
Mitosis
Zygote
SporesGametes
MEIOSIS FERTILIZATION
Diploidmulticellularorganism(sporophyte)
Haploid multi-cellular organism(gametophyte)
(b) Plants and some algae
Terms to know. . .
Somatic vs germ line cells Chromosomes (13.6)
Chromatids Homologous Autosomes vs sex chromosomes
Locus
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)
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)
Different Chromosome Numbers Are Found in One Organism
Gametes contain half as many chromosomes as somatic cells
Zygotes are produced by fusion of gametes Fusion of gametes is called fertilization or syngamy Meiosis serves to stabilize the chromosomes number Is a reduction division process Gametes are haploid and possess a single set of genetic material
An individual inherits genes from its father and its mother
I.Sexual Reproduction Varies by Kingdom A. Unicellular organisms 1. Individual cells function directly as
gametes 2. Zygote may divide mitotically or meiotically B. Plants 1. Haploid cells are produced through meiosis 2. Cells divide mitotically to form multicellular
haploid phase 3. Special haploid cells differentiate into
eggs or spermC. Animals
1. Gamete-producing cells differentiate from somatic cells early
2. Referred to as germ line cells 3. Somatic cells are diploid and reproduce by mitosis 4. Diploid gamete-producing cells, produce
haploid gametes by meiosis
If you think you can you can.
If you think you can’t you're right.
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
QuickTime™ and ampeg4 decompressor
are needed to see this picture.
QuickTime™ and ampeg4 decompressor
are needed to see this picture.
Meiosis I
Interphase: replication Each chromosome = 2 sister chromatids
Prophase I: Condensation of chromatin Synapsis Tetrads form Crossing over @ chiasmata Centrosomes separate, spindles form, bind to
kinetochores
Meiosis I
Metaphase I: Tetrads line up on metaphase plate
Anaphase I: Chromosomes (each = 2 sister chromatids) move to poles
Pulled along fibers by kinetochore Centromeres don’t separate
Telophase/cytokinesis Cleavage furrow N set of chromosomes @ each pole DAUGHTER CELLS ARE HAPLOID
Fig. 13-8bFig. 13-8b
Prophase I Metaphase I
Centrosome(with centriole pair)
Sisterchromatids Chiasmata
Spindle
Centromere(with kinetochore)
Metaphaseplate
Homologouschromosomes
Fragmentsof nuclearenvelope
Microtubuleattached tokinetochore
Fig. 13-UN4Fig. 13-UN4
Fig. 13-8cFig. 13-8c
Anaphase ITelophase I and
Cytokinesis
Sister chromatidsremain attached
Homologouschromosomesseparate
Cleavagefurrow
Fig. 13-8dFig. 13-8d
Prophase II Metaphase II Anaphase II Telophase II andCytokinesis
Sister chromatidsseparate Haploid daughter cells
forming
Meiosis II(NO INTERPHASE) Prophase II
New spindle fibers form Chromosomes move to middle
Metaphase II: Chromosomes on metaphase plate
Anaphase II: Centromeres/sister chromatids separate Each chromosome now = 1 chromatid
Telophase II/cytokinesis Nuclear membrane forms
Fig. 13-8eFig. 13-8e
Prophase II Metaphase II
Fig. 13-8fFig. 13-8f
Anaphase IITelephase II and
Cytokinesis
Sister chromatidsseparate Haploid daughter cells
forming
Fig. 13-8Fig. 13-8
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
Fig. 13-UN1Fig. 13-UN1
Prophase I: Each homologous pair undergoessynapsis and crossing over between nonsisterchromatids.
Metaphase I: Chromosomes line up as homolo-gous pairs on the metaphase plate.
Anaphase I: Homologs separate from each other;sister chromatids remain joined at the centromere.
Fig. 13-11-2Fig. 13-11-2
SUMMARY
MeiosisMitosisProperty
DNAreplication
Number ofdivisions
Occurs during interphase beforemitosis begins
One, including prophase, metaphase,anaphase, and telophase
Synapsis ofhomologouschromosomes
Does not occur
Number ofdaughter cellsand geneticcomposition
Two, each diploid (2n) and geneticallyidentical to the parent cell
Role in theanimal body
Enables multicellular adult to arise fromzygote; produces cells for growth, repair,and, in some species, asexual reproduction
Occurs during interphase before meiosis I begins
Two, each including prophase, metaphase, anaphase, andtelophase
Occurs during prophase I along with crossing overbetween nonsister chromatids; resulting chiasmatahold pairs together due to sister chromatid cohesion
Four, each haploid (n), containing half as many chromosomesas the parent cell; genetically different from the parentcell and from each other
Produces gametes; reduces number of chromosomes by halfand introduces genetic variability among the gametes
OOGENESIS/SPERMATOGENESIS
QuickTime™ and ampeg4 decompressor
are needed to see this picture.
QuickTime™ and ampeg4 decompressor
are needed to see this picture.
Genetic Variation
Independent assortment of maternal/paternal chromosomes (13.9) How many pairs in a human?!?!?
Crossing over Exchange b/w homologous chromosmes Recombinant: genetic info from 2 sources Sister chromatids identical
Random fertilization
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.