mitosis 2.0

• The cell cycle is a repeated pattern of growth and division that occurs in eukaryotic cells.
• Mitosis - consists of two phases: Interphase and Mitotic division(cell division)
• Cells have distinct phases of growth, reproduction, and normal functions.
• The cell cycle has four main stages.
• The cell cycle is a regular pattern of growth, DNA replication, and cell division.
• Cells spend the majority of their cell cycle in interphase.
• The purpose of interphase is for cell growth.
• By the end of interphase a cell has two full sets of DNA (chromosomes) and is large enough to begin the division process.
• Three major checkpoints in the cell cycle are Gap 1, Gap 2, and M division.
• –Gap 1 (G1 ): cell growth and normal functions
• –Gap 2 (G2 ): additional growth (chromatids become replicated chromosomes)
• –Mitosis (M): includes division of the cell nucleus (mitosis) and division of the `cell cytoplasm (cytokinesis)
• Mitosis occurs only if the cell is large enough and the DNA undamaged.
• Chromosomes condense at the start of mitosis.
• DNA wraps around proteins (histones) that condense it.
• In a typical human cell, there is about 6.5 feet of DNA!
• The purpose of mitosis is cell division: making two cells out of one.
• Each cell has to have its own cytoplasm and DNA.
• The DNA is replicated in interphase when two chromosome strands became four strands (two strands per chromatid).
• In mitosis the four strands (two sister chromatid) have to break apart so that each new cell only has one double-stranded chromosome.
• Two sister chromatids together make a chromosome
• DNA plus proteins is called chromatin.
• One half of a duplicated chromosome is a chromatid
• Sister chromatids are held together at the centromere.
• Telomeres protect DNA and do not include genes.
• Mitosis divides the cell’s nucleus in four phases.

  – Prophase

  – Metaphase

  – Anaphase

  – Telophase
• Prophase is characterized by four events:
• Prophase - Chromosomes condense and are more visible.
• Prophase - The nuclear membrane (envelope) disappears.
• Prophase - Centrioles have separated and taken positions on the opposite poles of the cell.
• Prophase - Spindle fibers form and radiate toward the center of the cell.
• During prophase, chromosomes condense and spindle fibers form.
• Metaphase is the shortest phase of mitosis and is characterized by two events
• Metaphase - Chromosomes line up across the middle of the cell.
• Metaphase - Spindle fibers connect the centromere of each sister chromatid to the poles of the cell
• During metaphase, chromosomes line up in the middle of the cell.
• Anaphase is characterized by three events
• Anaphase - Centromeres that join the sister chromatids split.
• Anaphase - Sister chromatids separate becoming individual chromosomes.
• Anaphase - Separated chromatids move to opposite poles of the cell.