BIO NOTES - Meiosis
● As mentioned, following meiosis II, the haploid cells become gametes in animals
● In plants, they become spores, reproductive cells that develop into new
multicellular structures without the need to fuse with another reproductive cell.
○ The multicellular structure is the haploid generation, which produces
gametes.
○ The resulting zygote develops into a diploid gen.eration.
○ Therefore, plants have both haploid and diploid phases in their life cycle,
and plants are said to exhibit an alternation of generations
■ In most
● Prophase I
○ Homologous chromosomes pair during synapsis.
● Metaphase I
○ Homologous chromosome pairs align at the metaphase plate.
● Anaphase I
○ Homologous chromosomes separate, pulled to opposite poles by
centromeric spindle fibers.
● Telophase I
○ Daughter cells have one chromosome from each homologous pair.
● Interkinesis
○ Chromosomes still consist of two chromatids.
● Cells from Prophase II
○ Meiosis I
■ Cells have one chromosome from each homologous pair.
● Metaphase II
○ Chromosomes align at the metaphase plate.
● Anaphase II
○ Daughter chromosomes move toward the poles.
● Telophase II
○ Spindle disappears, nuclei form, and cytokinesis takes place.
● Daughter Cells
, ○ Meiosis results in four haploid daughter cells.
● Stages of Meiosis.
○ When diploid homologous chromosomes pair during meiosis I,
crossing-over occurs, as represented by the exchange of color.
○ Pairs of homologous chromosomes separate during meiosis I, and
chromatids separate, becoming haploid daughter chromosomes, with two
copies of each during meiosis II.
○ Following meiosis II and the separation of sister chromatids, four haploid
daughter cells are produced.
● Meiosis Compared to Mitosis
○ Sister chromatids separate.
● Prophase I
○ Synapsis and crossing-over occur.
● Metaphase I
○ Homologues align independently.
● Anaphase I
○ Homologues separate.
● Telophase I
○ Daughter cells form.
● There are many similarities between the processes of mitosis. In both processes:
○ An orderly series of stages, including prophase, prometaphase,
metaphase, and telophase are involved in the sorting and divison of the
chromosomes.
○ The spindle fibers are active in sorting the chromosomes.
○ Cytokinesis follows the end of the process to divide the cytoplasm
between the daughter cells.
○ However, the function of mitosis and meiosis in an organism is very
different. Mitosis maintains the chromosome number
● Meiosis I compared to mitosis.
● As mentioned, following meiosis II, the haploid cells become gametes in animals
● In plants, they become spores, reproductive cells that develop into new
multicellular structures without the need to fuse with another reproductive cell.
○ The multicellular structure is the haploid generation, which produces
gametes.
○ The resulting zygote develops into a diploid gen.eration.
○ Therefore, plants have both haploid and diploid phases in their life cycle,
and plants are said to exhibit an alternation of generations
■ In most
● Prophase I
○ Homologous chromosomes pair during synapsis.
● Metaphase I
○ Homologous chromosome pairs align at the metaphase plate.
● Anaphase I
○ Homologous chromosomes separate, pulled to opposite poles by
centromeric spindle fibers.
● Telophase I
○ Daughter cells have one chromosome from each homologous pair.
● Interkinesis
○ Chromosomes still consist of two chromatids.
● Cells from Prophase II
○ Meiosis I
■ Cells have one chromosome from each homologous pair.
● Metaphase II
○ Chromosomes align at the metaphase plate.
● Anaphase II
○ Daughter chromosomes move toward the poles.
● Telophase II
○ Spindle disappears, nuclei form, and cytokinesis takes place.
● Daughter Cells
, ○ Meiosis results in four haploid daughter cells.
● Stages of Meiosis.
○ When diploid homologous chromosomes pair during meiosis I,
crossing-over occurs, as represented by the exchange of color.
○ Pairs of homologous chromosomes separate during meiosis I, and
chromatids separate, becoming haploid daughter chromosomes, with two
copies of each during meiosis II.
○ Following meiosis II and the separation of sister chromatids, four haploid
daughter cells are produced.
● Meiosis Compared to Mitosis
○ Sister chromatids separate.
● Prophase I
○ Synapsis and crossing-over occur.
● Metaphase I
○ Homologues align independently.
● Anaphase I
○ Homologues separate.
● Telophase I
○ Daughter cells form.
● There are many similarities between the processes of mitosis. In both processes:
○ An orderly series of stages, including prophase, prometaphase,
metaphase, and telophase are involved in the sorting and divison of the
chromosomes.
○ The spindle fibers are active in sorting the chromosomes.
○ Cytokinesis follows the end of the process to divide the cytoplasm
between the daughter cells.
○ However, the function of mitosis and meiosis in an organism is very
different. Mitosis maintains the chromosome number
● Meiosis I compared to mitosis.
