Cell Cycle & Mitosis

• Genetics is the study of heredity and hereditary variation
• The genome is the genetic material of cell-organisms
• Sisters chromatids are paired copies of chromosomal DNA
• The centromere is the point of close contact of sister chromatids
• The G1 phase of the cell cycle is general function and metabolism
• The S-Phase of the cell cycle is replication of DNA
• The G2 phase of the cell cycle is waiting for chromosome segregation
• In prophase, the mitotic spindle is forming and centrosomes separate. Chromatin condenses and sister chromatids are visible
• In prometaphase, the nuclear envelope has fragmented and microtubules enter the nuclear area. The chromosomes are fully condensed
• In Metaphase, the centrosomes are at opposite poles. The microtubules connect centrioles to centrosomes and chromosomes align on the metaphase plate
• In Anaphase, the cell elongates as non-kinetochore microtubules lengthen. Sister chromatids are pulled apart to opposite poles
• In telophase, the nuclear envelopes reappear and chromosomes decondense
• In cytokinesis, cytoplasms separate
• The cell cycle is regulated by a synchronising molecular cycle:

  1. Cyclins - Regulator proteins produced during the cell cycle in response to signals
  2. CdKs - Cyclin-dependent kinases, enzymes which add phosphate to downstream molecules and are activated by cyclin
  3. MPF - Maturation Promoting Factor, controls G2-M checkpoint
• Cancer involves a loss of cell cycle controls when cells do not obey normal regulatory signals. Transformation occurs when mutations lead to loss of control. Cancer occurs when malignant cells form tumours, blocking organ function. Cells lose anchorage dependence & density dependent inhibition.
• The kinetochore is a complex protein structure that forms on the centromere of a chromatid during cell division and ensures accurate segregation of chromosomes into daughter cells