Cell Cycles to Gametes

• Prokaryote characteristics:

  • bacteria and some algae
  • no nuclear membrane
  • no organelles
  • circular chromosome
  • naked DNA
  • haploid
  • no mitotic apparatus; divide by fission
• eukaryote characteristics:

  • all "higher" organisms
  • have cells, each with a nucleus
  • have organelles
  • linear chromosomes
  • have mitosis and meiosis
• consequences of mitosis:

  • all chromosomes duplicate and the copies separate to daughter cells
  • each daughter cell has the same genotype
• mitosis: 2N two identical 2N cells
• consequences of meiosis:

  • homologous chromosomes pair in M1
  • partners of each pair go to opposite poles
  • in M2, the chromatids of each chromosome go to opposite poles
• meiosis: 2N four 1N cells in 2 divisions
• cell cycle in eukaryotes: G1, S, G2, M
• interphase: G1, S, G2
• G1 and G2 are gap phases
• S phase: synthesis
• G1 checkpoint checks for:

  • cell size
  • nutrients
  • growth factors
  • DNA damage
• G2 checkpoint checks for:

  • cell size
  • DNA replication
• spindle assembly checkpoint checks for:

  • chromosome attachment to spindle
• short arm: P
• long arm: Q
• signs that mitosis is about to begin:

  • centriole has duplicated
  • poles form
• metaphase: middle
• anaphase: back
• telophase: end
• The number of chromosomes is defined by the number of centromeres
• centrioles: microtubules in the typical 9 sets of 3 arrangements as seen in animal cells
• Meiosis only occurs in germline cells
• synapsis: homologous chromosomes pair "gene-for-gene" throughout the length of the homologs
• meiosis: prophase, metaphase, anaphase, telophase
• synapsis: the point for point pairing of homologous chromosomes
• Synapsis occurs during meiosis I
• T/F:

  Meiosis in human females actually begins before birth.

  True
• How many gametes are expected from each cell that undergoes meiosis in a human male?

  4
• How many gametes are expected from each cell that undergoes meiosis in a human female?

  1
• epistasis: masking the expression of one gene by a completely different gene