Bio- Meiosis

Review of Mitosis

• chromosomes occur in homologous pairs

• chromosomes duplicate

  • 2 parts are chromatids

• sister chromatids separate

• produce 2 new nuclei

• each daughter cell is identical to the other and to the parent

Chromosome Number

• occur in pairs

• diploid- cell that contains pairs of chromosomes

  • represented by 2n

• human diploid number is 46

• Haploid- single copies of gametes

  • represented by n

• human haploid number is 23

Overview of Meiosis

• Chromosomes duplicate and divide

  • mitosis CHROMATIDS divide

• without duplication chromatids divide

• causes reduction in chromosomes

• creates 4 haploid cells

Meiosis 1

• chromosomes duplicate

• Tetrad- pairs of homologous pairs of chromosomes

• chromosomes in tetrad exchange portions of their chromatids

  • cross over

• cross over causes new gene combos

• after cross over chromosomes separate

• produces cells with 1 set of chromosomes

• 2 resulting cells are different from each other and the original

Meiosis

• DNA not replicated

• chromosomes line up in center

• separate and move to opposite sides

• forms 4 haploid cells