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Chromosomes begin to condense, and homologs loosely pair along their lengths, aligned gene by gene
prophase I
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crossing over (the exchange of corresponding segments of DNA molecules by nonsister chromatids) is completed while homologs are in synapsis, held tightly together by proteins along their lengths
prophase I
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synapsis ends in mid- (this stage), and the chromosomes in each pair move apart slightly
prophsae I
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each homologous pair has one or more chiasmata, points where crossing over has occurred and the homologs are srill associated due to cohesion between sister chromatids (sister chromatid cohesion)
prophase I
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centrosome movement, spindle formation, and nuclear envelope breakdown occur as in mitosis
prophaseI
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In late (this phase), microtubules from one pole or the other attach to the two kinetochores, protein structures at the centromeres of the two homologs. The homologous pairs then move toward the metaphase plate
prophase I
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pairs of homologous chromosomes are now arranged on the metaphase plate, with one chromosome in each pair facing each pole
metaphase I
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both chromatids of one homolog are attached to kinetochore microtubules from one pole; those of the other homolog are attached to microtubules from the opposite pole
metaphase I
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breakdown of proteins responsible for sister chromatid cohesion along chromatid arms allows homologs to separate
anaphase I
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the homologs move toward opposite poles, guided by the spindle apparatus
anaphase I
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sister chromatid cohesion persists at the centromere, causing chromatids to move as a unit toward the same pole
anaphase I
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at the beginning of this phase, each half of the cell has a complete haploid set of replicated chromosomes. Each chromosome is composed of two sister chromatids; one or both chromatids include regions of nonsister chromatid DNA
telophsae I and cytokinesis
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this (division of the cytoplasm) usually occurs simultaneously with this phsae, forming two haploid daughter cells
telophse I and cytokinesis
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in animal cells, a cleavage furrow forms (in plant cells, a cell plate forms.)
telophase I and cytokinesis
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in some species, chromosomes decondense and the nuclear envelope re-forms
telophse I and cytokinesis
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no replication occurs between meiosis I and meiosis II
telophsae I and cytokinesis
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a spindle apparatus forms
prophase II
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in late this phase, chromosomes, each still composed of two chromatids associated at the centromere, move toward the metaphase II plate
prophase II
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the chromosomes are positioned on the metaphsae plate as in mitosis
metaphse II
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because of crossing over in meiosis I, the two sister chromatids of each chromsome are not genetically identical
metaphse II
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the kinetochores of sister chromatids are attached to microtubules, extending from opposite poles
metaphase II
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breakdown of proteins holding the sister chromatids together at the centromere allows the chromatids to separate. the chromatids move toward opposite poles as individual chromosomes
ananpahse II
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nuclei form, the chromosomes begin decondensing and cytokinesis occurs
telophase II and cytokinesis
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the meiotic division of one parent cell produces four daughter cells, each with a haploid set of (unreplicated) chromosomes
telophase II and cytokinesis
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each of the four daughter cells genetically distinct from the other daughter cells and from the parent cell
telophase II and cytokinesis
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