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Interphase, G1 phase
  • cell grows in prepartation for DNA replication, until prepared to undergo DNA rep. in S phase
Interphase, S phase
  • cell continues to grow
  • synthesizes proteins and enzymes that are involved in DNA rep.
  • after DNA is Rep., then cell contains 2x the # of chromosomes and is ready for G2 phase
  • chromatin fibers become coiled into chromosomes with each chromosome having two chromatids joined at a centromere.
  • mitotic spindle, composed of microtubules and proteins, form in cytoplasm
  • mitotic spindle surround each centriole pair
  • two pair of centrioles move away from one another toward opposite ends of cell due to the lengthening of microtubules that form between them.
  • nuclear membrane disappears
  • two pair of centrioles align at opposite poles of cell
  • polar fibers continue to extend from poles to center cell
  • Chromosomes move randomly until they attach to polar fibers from both side of centromeres
  • chromosomes align at metaphase plate at right angles to the spindle poles
  • chromosomes are held at metaphase plate by equal forces of polar fibers pushing on centromeres of chromosomes.
  • paired centromeres in ea. chromosome begin to move apart
  • once sister chromatids separate, ea. is considered a full chromosome (daughter)
  • thru spindle aparatus, daughter chrom.move to the poles at opposite ends of cell
  • daughter chromosome migrate centromere first,and kinetochore fibers become shorter as chrom.'s near pole
  • cells start to move apart
  • polar fibers continue to lengthen
  • nuclei begin to form on opposite poles
  • nuclear envelopes of nuclei is formed from reminants of parent cells endomembrane system
  • nucleoli reappear
  • chromatin fibers of chromosomes start to uncoil
After G1, S phases Prophase 1 starts
  • chromatin condenses
  • ea. chromosome consist of two sister chromatids
  • crossing over occurs
Metaphase 1
  • homologous chromosomes align at equatorial plate
Anaphase 1
  • homologous pairs separate with sister chromatids remaining together
Telophase 1
  • two daughter cells formed with ea. daughter cell containing only one chromosome of homologous pair
Second division mieosis : gamete formation
Prophase 2
DNA does not replicate
Metaphase 2
chromosomes align at equatorial plate
Anaphase 2
centromeres divide and sister chromatids migrate separately to ea. pole
Telophase 2
cell division complete, four haploid cells are obtained
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