CLASE: DIVISI N CELULAR

2. HERENCIA DEL MATERIAL GENÉTICO EL ADN PUEDE SER HEREDADO A TRAVÉS DE LA MITOSIS: SE TRANSFIER DE CÉLULA EN CÉLULA EN UN MISMO ORGANISMO (RERODUCCIÓN ASEXUAL O SOMÁTICA). División ADN y celular.swf A TRAVÉS DE LA MEIOSIS: SE TRANSFIERE POR LOS GAMETOS DE UN ORGANISMO A OTRO (RERODUCCIÓN SEXUAL O GÁMICA).

3. Ciclo celular eucariótico Figure: 11.9 Title: The eukaryotic cell cycle Caption: The eukaryotic cell cycle consists of two major phases, interphase and cell division. Each is divided into subphases. Figure: 11.9 Title: The eukaryotic cell cycle Caption: The eukaryotic cell cycle consists of two major phases, interphase and cell division. Each is divided into subphases.

4. Fases de la Mitosis 1: Figure: 11.10 Title: The cell cycle in a plant cell Caption: The eukaryotic cell cycle consists of two major phases, interphase and cell division. Each is divided into subphases. Figure: 11.10 Title: The cell cycle in a plant cell Caption: The eukaryotic cell cycle consists of two major phases, interphase and cell division. Each is divided into subphases.

5. Separación de las cromátidas hermanas Durante la metafase, las cromátidas hermanas se mantienen unidas al centrómero. Al final de la metafase, el centrómero libera a las cromátidas hermanas. En la anafase, ellas se desplazan hacia los polos opuestos.

6. Fases de la Mitosis, 2

7. MITOSIS:PROFASE Y METAFASE Figure: 11.11a-d Title: The cell cycle in an animal cell Caption: (a) Late interphase: The chromosomes have been duplicated but remain elongated and relaxed within the nucleus. The centrioles have also been duplicated. (b) Early prophase: The chromosomes condense, shortening and thickening. The centrioles begin to move apart, and the spindle microtubules begin to form between them. (c) Late prophase: The nucleolus disappears; the nuclear envelope breaks down, and the spindle microtubules attach to the kinetochore of each sister chromatid (red spot). (d) Metaphase: Interactions between the kinetochores and the microtubules have lined up the chromosomes at the cell’s equator. Figure: 11.11a-d Title: The cell cycle in an animal cell Caption: (a) Late interphase: The chromosomes have been duplicated but remain elongated and relaxed within the nucleus. The centrioles have also been duplicated. (b) Early prophase: The chromosomes condense, shortening and thickening. The centrioles begin to move apart, and the spindle microtubules begin to form between them. (c) Late prophase: The nucleolus disappears; the nuclear envelope breaks down, and the spindle microtubules attach to the kinetochore of each sister chromatid (red spot). (d) Metaphase: Interactions between the kinetochores and the microtubules have lined up the chromosomes at the cell’s equator.

8. MitosisAnafase – Citocinesis: fases mitosis: mitosis y citoquinesis.swf Figure: 11.11e-I Title: The cell cycle in an animal cell Caption: (e) Anaphase: Chromatids separate at the centromere, becoming independent chromosomes that move toward the opposite poles of the cell. The free spindle microtubules slide past one another, pushing the poles farther apart. (f) Telophase: One complete set of chromosomes reaches each pole. The chromosomes relax into their extended state, the spindle microtubules begin to disappear, and the nuclear envelopes begin to re-form. (g) Cytokinesis: At the end of telophase, the cytoplasm is divided along the equator of the parent cell, with each daughter cell receiving one nucleus and about half the original cytoplasm. (h) Interphase of daughter cells: The daughter cells enter interphase. The spindle microtubules disappear, the nuclear envelope re-forms, the chromosomes finish extending, and the nucleolus reappears. Figure: 11.11e-I Title: The cell cycle in an animal cell Caption: (e) Anaphase: Chromatids separate at the centromere, becoming independent chromosomes that move toward the opposite poles of the cell. The free spindle microtubules slide past one another, pushing the poles farther apart. (f) Telophase: One complete set of chromosomes reaches each pole. The chromosomes relax into their extended state, the spindle microtubules begin to disappear, and the nuclear envelopes begin to re-form. (g) Cytokinesis: At the end of telophase, the cytoplasm is divided along the equator of the parent cell, with each daughter cell receiving one nucleus and about half the original cytoplasm. (h) Interphase of daughter cells: The daughter cells enter interphase. The spindle microtubules disappear, the nuclear envelope re-forms, the chromosomes finish extending, and the nucleolus reappears.

9. Citocinesis de una célula ciliada Figure: 11.12b Title: Cytokinesis in an animal cell Caption: Cytokinesis has almost separated the two daughter cells. Figure: 11.12b Title: Cytokinesis in an animal cell Caption: Cytokinesis has almost separated the two daughter cells.

12. LA REPRODUCCIÓN SEXUAL UTILIZA UN TIPO ESPECIAL DE DIVISIÓN CELULAR: LA MEIOSIS Características de la meiosis Ocurre en las células sexuales y produce gametos Como resultado de la división se obtienen células haploides Involucra dos divisiones secuenciales y da como resultado 4 células (gametos o esporas) Produce células que son genéticamente diferentes.

13. Meiosis I Figure: 11.14a-d Title: The details of meiotic cell division Caption: In meiotic cell division (meiosis and cytokinesis), the homologous chromosomes of a diploid cell are separated, producing four haploid daughter cells. Each daughter cell contains one member of each pair of parental homologous chromosomes. In these diagrams, two pairs of homologous chromosomes are shown, large and small. The yellow chromosomes are from one parent (for example, the father), and the violet chromosomes are from the other parent. (a) Prophase I. Duplicated chromosomes condense. Homologous chromosomes pair up and chiasmata occur as chromatids of homologues exchange parts. The nuclear envelope disintegrates, and spindle microtubules form. (b) Metaphase I. Paired homologous chromosomes line up along the equator of the cell. One homologue of each pair faces each pole of the cell and attaches to spindle microtubules via its kinetochore (red). (c) Anaphase I. Homologues separate, one member of each pair going to each pole of the cell. Sister chromatids do not separate. (d) Telophase I. Spindle microtubules disappear. Two clusters of chromosomes have formed, each containing one member of each pair of homologues. The daughter nuclei are therefore haploid. Cytokinesis commonly occurs at this stage. There is little or no interphase between meiosis I and meiosis II. Figure: 11.14a-d Title: The details of meiotic cell division Caption: In meiotic cell division (meiosis and cytokinesis), the homologous chromosomes of a diploid cell are separated, producing four haploid daughter cells. Each daughter cell contains one member of each pair of parental homologous chromosomes. In these diagrams, two pairs of homologous chromosomes are shown, large and small. The yellow chromosomes are from one parent (for example, the father), and the violet chromosomes are from the other parent. (a) Prophase I. Duplicated chromosomes condense. Homologous chromosomes pair up and chiasmata occur as chromatids of homologues exchange parts. The nuclear envelope disintegrates, and spindle microtubules form. (b) Metaphase I. Paired homologous chromosomes line up along the equator of the cell. One homologue of each pair faces each pole of the cell and attaches to spindle microtubules via its kinetochore (red). (c) Anaphase I. Homologues separate, one member of each pair going to each pole of the cell. Sister chromatids do not separate. (d) Telophase I. Spindle microtubules disappear. Two clusters of chromosomes have formed, each containing one member of each pair of homologues. The daughter nuclei are therefore haploid. Cytokinesis commonly occurs at this stage. There is little or no interphase between meiosis I and meiosis II.

14. Meiosis II Figure: 11.14e-I Title: The details of meiotic cell division Caption: In meiotic cell division (meiosis and cytokinesis), the homologous chromosomes of a diploid cell are separated, producing four haploid daughter cells. Each daughter cell contains one member of each pair of parental homologous chromosomes. In these diagrams, two pairs of homologous chromosomes are shown, large and small. The yellow chromosomes are from one parent (for example, the father), and the violet chromosomes are from the other parent. (e) Prophase II. If chromosomes have relaxed after telophase I, they recondense. Spindle microtubules re-form and attach to the sister chromatids. (f) Metaphase II. Chromosomes line up along the equator, with sister chromatids of each chromosome attached to spindle microtubules that lead to opposite poles. (g) Anaphase II. Chromatids separate into independent daughter chromosomes, one former chromatid moving toward each pole. (h) Telophase II. Chromosomes finish moving to opposite poles. Nuclear envelopes re-form, and the chromosomes become extended again (not shown here). (i) Four haploid cells. Cytokinesis results in four haploid cells, each containing one member of each pair of homologous chromosomes (shown here in condensed state). Figure: 11.14e-I Title: The details of meiotic cell division Caption: In meiotic cell division (meiosis and cytokinesis), the homologous chromosomes of a diploid cell are separated, producing four haploid daughter cells. Each daughter cell contains one member of each pair of parental homologous chromosomes. In these diagrams, two pairs of homologous chromosomes are shown, large and small. The yellow chromosomes are from one parent (for example, the father), and the violet chromosomes are from the other parent. (e) Prophase II. If chromosomes have relaxed after telophase I, they recondense. Spindle microtubules re-form and attach to the sister chromatids. (f) Metaphase II. Chromosomes line up along the equator, with sister chromatids of each chromosome attached to spindle microtubules that lead to opposite poles. (g) Anaphase II. Chromatids separate into independent daughter chromosomes, one former chromatid moving toward each pole. (h) Telophase II. Chromosomes finish moving to opposite poles. Nuclear envelopes re-form, and the chromosomes become extended again (not shown here). (i) Four haploid cells. Cytokinesis results in four haploid cells, each containing one member of each pair of homologous chromosomes (shown here in condensed state).

15. Entrecruzamiento crosing-over.swfLos homólogos se aparean. Cadenas de proteínas “cierran” los cromosomas homólogos como una cremallera. Las enzimas de recombinación cortan y separan las cromátidas y las vuelven a unir. Los homólogos se separan con nuevas cominaciones de genes. Figure: 11.15 Title: The mechanism of crossing over Caption: 1) Homologous chromosomes pair up side by side. 2) One end of each chromosome binds to the nuclear envelope. Protein strands “zip” homologous chromosomes together. 3) Homologous chromosomes are fully joined by protein strands. 4) Recombination enzymes bind to the chromosomes. Recombination enzymes snip chromatids apart and reattach the chromatids. Chiasmata are formed when one end of a chromatid of a paternal chromosome (yellow) is attached to the other end of a chromatid of a maternal chromosome (violet). 5) The protein strands and recombination enzymes leave as the chromosomes condense. The chiasmata remain as locations where homologous chromosomes are twisted around each other, helping to hold homologues together. Figure: 11.15 Title: The mechanism of crossing over Caption: 1) Homologous chromosomes pair up side by side. 2) One end of each chromosome binds to the nuclear envelope. Protein strands “zip” homologous chromosomes together. 3) Homologous chromosomes are fully joined by protein strands. 4) Recombination enzymes bind to the chromosomes. Recombination enzymes snip chromatids apart and reattach the chromatids. Chiasmata are formed when one end of a chromatid of a paternal chromosome (yellow) is attached to the other end of a chromatid of a maternal chromosome (violet). 5) The protein strands and recombination enzymes leave as the chromosomes condense. The chiasmata remain as locations where homologous chromosomes are twisted around each other, helping to hold homologues together.

16. COMPARACIÓN DE LOS HUSOS FORMADOS DURANTE LA MITOSIS Y LA MEIOSIS I. Figure: 11.16 Title: A comparison of the spindles formed during mitosis and meiosis I Caption: (a) In mitosis, homologous chromosomes are not paired. The kinetochores of sister chromatids are attached to kinetochore microtubules that lead to opposite poles. When the sister chromatids separate during anaphase, the newly independent daughter chromosomes move to opposite poles of the cell. (b) In meiosis I, homologous chromosomes are paired. Both kinetochores of the sister chromatids of a single chromosome are attached to kinetochore microtubules that lead to the same pole. During anaphase I, sister chromatids of each chromosome remain together, moving to the same pole, but homologous chromosomes separate and move to opposite poles. Figure: 11.16 Title: A comparison of the spindles formed during mitosis and meiosis I Caption: (a) In mitosis, homologous chromosomes are not paired. The kinetochores of sister chromatids are attached to kinetochore microtubules that lead to opposite poles. When the sister chromatids separate during anaphase, the newly independent daughter chromosomes move to opposite poles of the cell. (b) In meiosis I, homologous chromosomes are paired. Both kinetochores of the sister chromatids of a single chromosome are attached to kinetochore microtubules that lead to the same pole. During anaphase I, sister chromatids of each chromosome remain together, moving to the same pole, but homologous chromosomes separate and move to opposite poles.

17. COMPARACIÓN MITOSIS MEIOSIS: COMPARACION DE MITOSIS Y MEIOSIS.swf Figure: 1.1 Title: A comparison of mitotic and meiotic cell divisions in animal cells Caption: In these diagrams, comparable phases are aligned. In both mitosis and meiosis, chromosomes are replicated during interphase. Meiosis I, with the pairing of homologous chromosomes, formation of chiasmata, exchange of chromosome parts, and separation of homologues to form haploid daughter nuclei, has no counterpart in mitosis. Meiosis II, however, is similar to mitosis. Figure: 1.1 Title: A comparison of mitotic and meiotic cell divisions in animal cells Caption: In these diagrams, comparable phases are aligned. In both mitosis and meiosis, chromosomes are replicated during interphase. Meiosis I, with the pairing of homologous chromosomes, formation of chiasmata, exchange of chromosome parts, and separation of homologues to form haploid daughter nuclei, has no counterpart in mitosis. Meiosis II, however, is similar to mitosis.

18. Escenarios de alineamiento de los cromosomas en la Metafase Figure: 11.UN16 Title: Shuffling of homologues in anaphase I and genetic variability Caption: Three pairs of homologous chromosomes will produce eight possible sets of chromosomes in anaphase I.Figure: 11.UN16 Title: Shuffling of homologues in anaphase I and genetic variability Caption: Three pairs of homologous chromosomes will produce eight possible sets of chromosomes in anaphase I.

19. Errores en la meiosis 1. No disyunción: Falla en la separación de los pares de cromosomas homólogos en la anafase de la meiosis I, por lo que los cromosomas no se agregan correctamente a las células hijas. a. Resultan gametos con un número anormal de cromosomas. b. Los embriones producto de la fusión de gametos con número anormal de cromosomas abortan espontáneamente y representan de 20% a 50% de todos los embarazos malogrados.

20. Errores en la meiosis: No disyunción de los autosomas a. Trisomía 21:Síndrome de Down b. Trisomía 13 :Síndrome de Patau c. Deleción del cromosoma 5: Síndrome de Cri du chat

21. No disyunción de los cromosomas sexuales a. Síndrome de Turner (XO) b. Trisomía X (XXX) c. Síndrome de Klinefelter (XXY)

28. ¿Qué procesos ocurren en espermatogénesis? Se diferencian las células germinales del embrión y se ubican en los túbulos seminíferos testículo. En la pubertad, las células germinales hacen mitosis y se transforman en espermatogonios Los espermatogonios, crecen y se transforman en espermatocitos I (2n, 4c) Los espermatocitos I, hacen la meiosis I y originan dos espermatocitos II ( n, 2c). Los espermatocitos II, hacen la meiosis II y originan 4 espermátidas (n, c). Las espermátidas, experimentan profundas transformaciones morfológicas y dan origen a 4 espermios funcionales (espermiohistogénesis).

30. TRABAJO EN EQUIPO: Después de haber consultado tu texto guía y haber analizado estas información, haz lo siguiente ¿Qué tipos de periodos o fases es posible reconocer en el ciclos celular y que caracteriza a dichos momentos de la división celular? Establece como mínimo 5 diferencias entre la interfase y la mitosis del ciclo celular. Indica los hechos más significativos que caracterizan a las siguientes fases de la meiosis: Profase, Metafase, Anafase, Telofase, Citocinesis. ¿Qué tipo de alteraciones podrían ocurrir, si en la anafase no se separaran las cromátidas hermanas de algunos de los cromosomas duplicados. Describe el significado de los siguientes conceptos: cromosomas, cromátidas, cromosomas homólogos, centríolos, huso mitótico, plano ecuatorial de la célula. Pinta en la fig. 5 con colores diferentes los cromosomas homólogos e indica en el mismo orden los procesos que hacen para llegar a los polos de la célula en la telofase. ¿Para qué ocurre la mitosis en tu organismo y, en los organismos unicelulares y en algunos vegetales?. Se afirma que la mitosis, está asociada de manera indirecta con la reproducción sexual de los seres vivos. Explica el sentido de esta afirmación. ¿Cuál es rol biológico de la meiosis? En órganos de tu cuerpo ocurre: Meiosis. Mitosis.

31. TRABAJO EN EQUIPO: 11. ¿Cuántas divisiones contempla la meiosis y que las caracteriza? Explica. 12. Nombra y describe todas las fases de la de la primera división meiótica y de la segunda división meiótica, haciendo una caracterización de cada una de ellas. 13. Indica como mínimo dos diferencias entre la Meiosis I y la Meiosis II. 14. Indica 8 diferencias entre la mitosis y la meiosis. 15. ¿Mediante que procesos la meiosis produce variabilidad de la información genética en las células resultantes? Explica. 16. Se dice que la meiosis se relaciona directamente con la reproducción sexual. Explica el sentido de esta afirmación. 17. Indica los procesos más significativos que ocurren en la ovogénesis y la espermatogénesis. 18 ¿En que se diferencia tu gametogénesis de la de tu sexo contrario? Explica. 19. ¿Qué tipo de alteraciones se pueden producir como consecuencia de una meiosis defectuosa? Explica 20. Explica el significado de los siguientes términos y /o símbolos: Ovogonios. Espermatogonios Espermatocitos I Espermatocitos II. Ovocitos I. Ovocitos II. Espermátidas 2n; 2c; 2n-4c; n; n-c. Polocitos I y II. 20. Haz un mapa conceptual con los conceptos más relevante de los contenidos de esta clase.