Meiosis
Transcript of Meiosis
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La Meiosis
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Características generales
• Ocurre en gónadas( testículos y ovarios).
• Permite formar gametos( ovocitos y espermios).
• Forma células de tipo haploides( n=23 cromosomas) tienen la mitad de cromosomas propio de la especie).
• A partir de una célula madre se forman 4 células hijas.
• Las células resultante son diferentes entre si.
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• Al finalizar la meiosis I, va a ocurrir una interfase II, también llamada intercinesis, en la cual pueden haber duplicación de organelos, si debe haber duplicación de centriolos, pero no debe ocurrir duplicación de material genético.
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Conceptos importantes1. crossing-over.
2. Permutación cromosomica.
3. Intercinesis.
4. Paquinema.
5. Meiosis reduccional.
6. Meiosis ecuacional
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Idiograma o
cariotipo fetal
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Fluorescent In-Situ Hybridization (FISH)
FISH de cromosomas humanos – “Chromosome Painting" -> Pintado cromosómico
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Fluorescent In-Situ Hybridization (FISH)
FISH de cromosomas humanos – “Chromosome Painting" -> Pintado cromosómico
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Especie 2n
Ser humano (Homo sapiens)Guisante (Pisum sativum)Mosca fruta (Drosophila melanogaster)Ratón doméstico (Mus musculus)Lombriz intestinal (Ascaris)Paloma (Columba livia)Boa constrictor (Constrictor constrictor)Grillo (Gryllus domesticus)Azucena de trompeta (Lilium longiflorum)Helecho indio (Ophioglossum reticulatum)
46148
402
80362224
1260
Número de cromosomas (2n) de algunas especies
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?¿Cómo se transmiten los
cromosomas a las células hijas
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Ciclo celularCiclo celular
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Mitosis y Meiosis:Mitosis y Meiosis:Mitosis y Meiosis:Mitosis y Meiosis:
La mitosis es la solución al problema de la división celular y la constancia en el número de cromosomas de las células hijas
La meiosis resuelve el problema de la presencia de dos padres (progenitores) en los organismos sexuales y la constancia del número de cromosomas entre generaciones
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Cromosoma metafásico formado por doscromátidas hermanas: DNA duplicado
El cromosomaen las células hijas tras la segregación
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MitosisMitosisMitosisMitosis
Etapas de la mitosis
Interfase Profase Metafase
Anafase Telofase
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MitosisMitosisMitosisMitosis
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Meiosis
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Meiosis
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Mitosis vs Meiosis
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Fuerza motora de la segregación
Imagen de célula humana con microtúbulos en verde, cromosomas (DNA) en azul, y cinetocoro en rojo
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Fuerza motora de la segregación
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Mitosis Mitosis vsvs Meiosis: Meiosis:Mitosis Mitosis vsvs Meiosis: Meiosis:
•Conservativa (2n) -> (2n)
•Una división (2 células hijas)
•No suele haber apareamiento cromosomas homológos (y no quiasma)
•Células no gaméticas
Mitosis Meiosis
•Reductiva (2n) -> (n)
•Dos divisiones (4 células hijas)
• Apareamiento cromosomas homológos (y quiasma -> entrecruzamiento)
•Células gaméticas
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Teoría cromosómica de la Teoría cromosómica de la herencia herencia
Teoría cromosómica de la Teoría cromosómica de la herencia herencia
•Los genes se encuentran en los cromosomas
•El lugar que ocupa un gen en un cromosoma se denomina locus
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Cromosomas homólogos en metafase. Nótese que (1) cada gen tiene cuatro copias debido a que el material genético se ha duplicado para llevar a cabo la mitosis (o la meiosis) y (2) cada alelo de un heterocigoto se encuentra en un cromosoma homólogo
A A a a