Meiosis

• Allele


  A variant form of a gene
• Haploid


  An organism that has one 'set' of chromosomes
• Diploid


  An organism that has two 'sets' of chromosomes
• In a haploid organism, there is one allele of each gene
• In a diploid organism, there are two alleles of each gene (one from each set of chromosomes)
• The gene pool of an organism represents the variety of alleles of genes present in that population
• Asexual reproduction


  Reproduction that creates genetically identical clones
• Sexual reproduction


  Reproduction that causes novel genetic combinations in offspring
• Asexual reproduction is better in a stable environment
• Gamete


  A haploid reproductive cell that is important for fertilization
• Life cycle of an organism


  1. Cell division (mitosis)

  2. Gamete production (meiosis)

  3. Gamete fusion (fertilization)
• Mitosis


  Cell division that produces genetically identical daughter cells
• Meiosis


  Cell division that produces genetically diverse haploid daughter cells
• Homologous chromosomes are identified in meiosis I
• Crossing over


  Exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis I
• Ways genetic diversity/recombination occurs in a sexual life cycle

  • Crossing over
  • Independent assortment of homologous chromosomes
  • Fertilization bringing genes from two parents together
• The genes of every organism are encoded on the chromosomes
• Haploid organisms have one set of chromosomes, diploid organisms have two sets of chromosomes
• The gene pool represents the variety of alleles present in a population
• Asexual reproduction


  Creates genetically identical clones
• Sexual reproduction


  Causes novel genetic combinations in offspring
• Asexual organisms rely on mutations to generate variation
• Fertilization combines haploid cells to form a diploid zygote
• Meiosis reduces the chromosome number from diploid to haploid
• Mitosis produces genetically identical daughter cells
• Meiosis produces genetically diverse haploid daughter cells
• Crossing over creates genetic variation by recombining maternal and paternal chromosomes
• Independent assortment of homologous chromosomes creates genetic variation
• Fertilization brings genes from two parents together, creating genetic variation
• Meiotic non-disjunction can result in chromosomal disorders like Klinefelter's and Turner's syndromes
• why is asexual reproduction better in a stable environment?

  all the offspring will be adapted to that environment
• what else does sexual reproduction cause?


  offspring to have different combination of genes than their parents