reduction of chromosomes. mitosis cell duplication (or reproduction) where one cell creates two...
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Reduction of Chromosomes
Cell duplication (or reproduction) where one cell creates two genetically identical daughter cells
Cellular reproduction, growth and repair
Occurs in all organisms
Daughter cells are genetically identical
There is one division Same number of chromosomes (2n) Steps: Interphase, Prophase,
Metaphase, Anaphase and Telophase
Cytokinesis in Telophase Centromeres split only once during
Anaphase
Division of a gonad (germ cell) with TWO nuclear fissions and creating four gametes with half the number of chromosomes
Sexual reproduction Occurs in humans (animals),
plants and fungi Daughter cells are genetically
different There are TWO divisions Half the number of chromosomes Steps: Interphase, Prophase I,
Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II
Cytokinesis in Telophase I and II Centromeres split during
Anaphase II, not Anaphase I
Meiosis
http://www.cellsalive.com/meiosis.htmInterphase: -the cell replicates its chromosomes
-each chromosome has two sister chromatids held together by a centromere
-chromosomes coil up and a spindle forms
-homologous chromosomes come together matched gene by gene forming a tetrad
Crossing Over may occur when chromatids exchange genetic material -this occurs two or three times per pair of homologous chromosomes
Crossing Over results in new combinations of alleles on a chromosomes
the centromere of each chromosome becomes attached to a spindle fiber
the spindle fibers pull the tetrads to the equator of the spindle
homologous chromosomes are lined up side by side as tetrads
homologous chromosomes separate and move to opposite ends of the cell
centromeres do not split this ensures that each new cell will receive
only one chromosome from each homologous pair
the spindle breaks down and the chromosomes uncoil
the cytoplasm divides to yield two new cells each cell has half the genetic information of
the original cell because it has only one homologous chromosome from each pair
a spindle forms in each of the two new cells and the fibers attach to the chromosomes
the chromosomes are pulled to the center of the cell and line up randomly at the equator
the centromere of each chromosome splitsthe sister chromatids separate and move to
opposite poles
-nuclei re-formthe spindles break downthe cytoplasm divides identical to mitosis (Meiosis II)
four haploid sex cells (n) from one original diploid cell (2n)
each haploid cell contains one chromosome from each homologous pair one from Mom and one from Dad
haploid cells will become gametes transmitting genes to offspring
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