meiosis

• Meiosis


  A type of cell division that produces daughter cells which are genetically different
• Meiosis


  1. Parent cell divides once

  2. Parent cell divides twice

  3. Results in 4 haploid daughter cells
• Haploid cells


  • Have one set of chromosomes
• Diploid cells


  • Have two sets of chromosomes
• Independent segregation


  Homologous chromosomes line up randomly at the equator during meiosis I, resulting in random distribution to daughter cells
• Crossing over


  Homologous chromosomes exchange genetic material during meiosis I, resulting in new combinations of alleles
• Meiosis introduces genetic variation through independent segregation and crossing over
• To identify meiosis in an organism's life cycle, look for the transition from diploid to haploid cells
• The number of possible chromosome combinations in gametes is 2^n, where n is the number of chromosome pairs
• The number of possible chromosome combinations in the resulting organism after fertilization is 2^(2n), where n is the number of chromosome pairs
• Humans have 23 chromosome pairs, resulting in over 8 million possible chromosome combinations in gametes and over 70 trillion possible combinations in the resulting organism
• Genetically identical humans can only occur in the case of identical twins