division meiosis
DESCRIPTION
Division MeiosisTRANSCRIPT
Meiosis Meiosis
Meiosis I y IIMeiosis I y II
2n
Diploide
Meiosis
Una célula madre diploide pasa por dos divisiones celulares dando origen a cuatro células hijas haploides con recombinación genética. Diapositiva 5
Diapositiva 2
Haploides (N)
CRECIMIENTO
EN QUE CELULAS OCURRE LA MEIOSIS
ANIMALES:de la línea germinativa en gónadas masculinas y
femeninas
VEGETALES: células madres: Megasporas y microsporas
HONGOS: células madres de esporas Diapositiva 5
INTERCINESIS (sin duplicación de ADN) MEIOSIS II (ecuacional)Diapositiva 17 PROFASE IIDiapositiva 17 METAFASE II (ubicación en la placa ecuatorial) ANAFASE II (separación de cromátidas y
migración a los polos) TELOFASE II CITOCINESIS (cuatro células hijas haploides y
con Material genético recombinado).Diapositiva 17LAS COMBINACIONES VARIAN SEGÚN LA
DISPOSICIÓN Y SEPARACION DE LOS CROMOSOMAS Diapositiva 17 Diapositiva 19
DescripciónDiapositiva 1 Diapositiva 3
Maternal set ofchromosomes (n = 3)
2n = 6
Paternal set ofchromosomes (n = 3)
Two sister chromatidsof one replicatedchromosomes
Two nonsister chromatids in a homologous pair
Pair of homologouschromosomes(one from each set)
Centromere
Centrosomes(with centriole pairs)
Nuclearenvelope
Chromatin
Chromosomes duplicate
INTERPHASE
METAPHASE I
Prophase Iof meiosis
Tetrad
Nonsisterchromatids
Chiasma,site of crossingover
Recombinantchromosomes
Metaphase I
Metaphase II
Daughtercells
Diapositiva 1
Fuente: www.bio.miami.edu
CIGOTENODiapositiva 3
Centrosomes(with centriole pairs)
Sisterchromatids
Chiasmata
Spindle
Centromere(with kinetochore)
Metaphaseplate
Homologouschromosomesseparate
Sister chromatidsremain attached
Microtubuleattached tokinetochore
Tetrad
Nuclearenvelope
Chromatin
Chromosomes duplicate
INTERPHASE MEIOSIS I: Separates homologous chromosomes
PROPHASE I METAPHASE I ANAPHASE I
Homologous chromosomes (red and blue) pair andexchange segments; 2n = 6in this example
Pairs of homologouschromosomes split up
Tetrads line up
Diapositiva 3
Sisterchromatids
Chiasmata
Spindle
Centromere(with kinetochore)
Metaphaseplate
Homologouschromosomesseparate
Sister chromatidsremain attached
Microtubuleattached tokinetochore
Tetrad
MEIOSIS I: Separates homologous chromosomes
PROPHASE I METAPHASE I ANAPHASE I
Homologous chromosomes (red and blue) pair andexchange segments; 2n = 6in this example
Pairs of homologouschromosomes split up
Tetrads line up
Diapositiva 3
Cleavagefurrow
MEIOSIS II: Separates sister chromatids
PROPHASE II METAPHASE II ANAPHASE IITELOPHASE I AND
CYTOKINESISTELOPHASE II AND
CYTOKINESIS
Sister chromatidsseparate
Haploid daughter cellsforming
Two haploid cellsform; chromosomesare still double
During another round of cell division, the sister chromatids finally separate;four haploid daughter cells result, containing single chromosomes
Diapositiva 4
Key
Maternal set ofchromosomes
Paternal set ofchromosomes
Possibility 1 Possibility 2
Combination 2Combination 1 Combination 3 Combination 4
Daughtercells
Metaphase II
Two equally probablearrangements ofchromosomes at
metaphase I
Diapositiva 4
Propase
Duplicated chromosome(two sister chromatids)
Chromosomereplication
2n = 6
Parent cell(before chromosome replication)
Chromosomereplication
MITOSIS MEIOSIS
Chiasma (site ofcrossing over) MEIOSIS I
Prophase I
Tetrad formed bysynapsis of homologouschromosomes
Tetradspositioned at themetaphase plate
Metaphase IChromosomes positioned at themetaphase plate
Metaphase
AnaphaseTelophase
Homologuesseparateduringanaphase I;sisterchromatidsremain together
Sister chromatidsseparate duringanaphase
Daughtercells of
meiosis I
Haploidn = 3
Anaphase ITelophase I
MEIOSIS II
Daughter cellsof mitosis
2n2n
n
Sister chromatids separate during anaphase II
n n n
Daughter cells of meiosis II
GAMETOGENESIS Diapositiva 21 Diapositiva 22
Fuente: www.bio.miami.edu
Diapositiva 22
Fuente: academic.pgcc.edu
IMPORTANCIA BIOLOGICA DE LA MEIOSIS
Intercambio de material genético Recombinación genética Variabilidad genética Materia prima para la evolución
Diapositiva 25
Errores meiErrores meióóticosticos
A.- A.- Homólogos sin desunir no se separan en meiosis 1
1.Resultados en aneuploide
2.Usualmente letal para el embrión
3.Trisomía 21, excepción que conduce al síndrome de Down.
B.- Cromosomas sexuales
1.Síndrome de Turner: monosomia X
2.Síndrome de Klinefelter: XXY