process of meiosis

• meiosis divides the number of chromosomes into halves in the formation of gametes hence is called reduction division
• each half of a duplicated chromosome is called chromatid
• sister chromatid - duplicated chromosomes attached to each other by a structure called centromere
• meiosis 1 - focuses on the division of homologous chromosomes to produce two haploid cells with duplicated chromosomes
• prophase 1

  • breaking down of nuclear envelope
  • spindle fibers bein to assemble
  • duplicated chromosomes condense
  • crossing over at point called chiasma
• metaphase 1

  • homologous chromosomes are randomly moved the spindle fibers to the equator of the cell
  • the lining up of 23 chromosomes
  • 223 or 388 608 combinations of chromosomes
• anaphase 1

  • homologous chromosomes separate from each other
  • chromosomes of each pair are pulled to the opposite sides of the cell by the action of spindle fibers
  • sister chromatids remain together and do not separate at their centromeres throughout meiosis 1
• telophase 1

  • individual chromosomes that have been pulled in opposite directions now gather at each pole
  • both poles contain one chromosome
  • there is reappearance of the nuclear membrane and disassembly of spindle fibers
  • the cytoplasm divides through cytokinesis
• meiosis 2 - to divide sister chromatids, resulting in sex cells with only half the chromosome number
• prophase 2

  • new spindle forms around the chromosome
  • the nuclear envelope breaks down
• metaphase 2

  • chromosomes line up along the equator through the spindle fiber
  • sister chromatids are still attached to the centromere
• anaphase 2

  • centromeres divide
  • sister chromatids are individually pulled apart, then move to the opposite poles of the cell
• telophase 2

  • nuclear envelope forms around each set of chromosomes at opposite ends of the cell
  • the spindle fiber breaks down and the cell undergoes cytokinesis
  • the result of meiosis is four haploid cells
• M1 - homologous chromosomes lines at the metaphase plate
• M2 - sister chromatids move away from each other
• M1 - crossing over
• M2 - chromatids are now at the opposite poles of the dividing cell
• M1 - homologous pair attach to the spindle fiber
• M2 - formation of 4 haploid cells