Biology: 2.1 Cell Division

Outline the stages of the cell cycle, including interphase (G1, S, G2), mitosis, and cytokinesis.

Interphase

• G1: growth; DNA transcription; protein synthesis
• S: DNA replication
• G2: preparation for division

Mitosis: the process by which the cell divides to form two genetically identical nuclei.
Cytokinesis: the process of dividing the cytoplasm to form two cells.

State that tumors (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue.

State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts.

Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase).
Prophase:

• Spindle microtubules are growing.
• Chromosomes are becoming shorter and fatter by supercoiling.
• Each chromosome consists of two identical chromatids formed by DNA replication in interphase and held together by a centromere.
• Spindle microtubules extend from each pole to the equator.
  

Metaphase:

• The nuclear membrane has broken down and chromosomes have moved to the equator.
• Spindle microtubules from both poles attach to each centromere, on opposite sides.
  

Anaphase:

• The centromeres have divided and the chromatids have become chromosomes.
• Spindle microtubules pull the genetically identical chromosomes to opposite poles.
  

Telophase:

• All chromosomes have reached the poles and nuclear membranes form around them.
• Spindle microtubules break down.

Explain how mitosis produces two genetically identical nuclei.

State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis.