Presentation on theme: "Mitosis & Meiosis. Cell Cycle G1 (Gap 1)- cells carry out normal metabolic activities for day to day functions. S (Synthesis)- DNA is replicated (duplicated,"— Presentation transcript:
Mitosis & Meiosis
Cell Cycle G1 (Gap 1)- cells carry out normal metabolic activities for day to day functions. S (Synthesis)- DNA is replicated (duplicated, copied). G2 (Gap 2)- cell prepares for cell division by doubling cell organelles.
Mitosis A stage of the cell cycle that involves the division of the nucleus into two new nuclei that contain identical copies of the genetic information. Mitosis is divided into 4 stages based on the cellular events: Prophase, Metaphase, Anaphase, Telophase. (PMAT) If you include Interphase (IPMAT – I phoned mom and talked)
Functions of Mitosis 1. Growth 2. Repair regenerate damaged tissues. 3. Regeneration of entire body parts simpler organisms. 4. Maintenance of the body. Mitosis and cytokinesis occur in our body cells (aka somatic cells)
Interphase Period of growth & development Hereditary information (DNA) copied (replicated / duplicated) Cells that do not divide (nerves) are always in interphase
Prophase DNA begins to shorten & thicken Now called chromatids/chromosomes Centromeres form Nuclear membrane breaks apart Spindle fibers begin to form
Metaphase Chromatids / chromosomes line up Centromere attaches to spindle fibers
Anaphase Centromeres divide Spindle fibers shorten Sister chromatid pairs separate – move to opposite ends of the cell.
Telophase Spindle fibers begin to disappear Chromosomes begin to uncoil Nuclear membrane starts to re-form Cell plate (plant cell) or Cleavage furrow (animal cell) becomes highly noticeable.
Cytokinesis (Cell Cutting) The division of the cytoplasm is know as cell cutting. This signals the end of Mitosis. After the cells membrane or wall forms a complete new barrier between the two sister cells. We would say cytokinesis has just occurred.
Results of Mitosis Division of nucleus Nuclei are identical to each other Same number & type of chromosomes
A type of reproduction - fission, budding, and regeneration - in which a new organism is produced from one parent and has DNA identical to the parent organism.
Asexual Reproduction Offspring produced from one organism Hereditary information is identical Mitosis is one form of asexual reproduction
A type of reproduction in which two sex cells, usually an egg and a sperm, join to form a zygote, which will develop into a new organism with a unique identity.
Meiosis The nucleus divides twice Meiosis I Meiosis II Final Product will be 4 cells from one parent that contains ½ the original amount of chromosomes as the parent.
Interphase Same as in Mitosis. Normal life cycle functions of the cell Divided into 3 stages: G1 (Gap 1)- Growth and development S (Synthesis Phase) - DNA is duplicated G2 (Gap 2)- Organelles double in preparation for separation
Prophase I DNA begins to shorten & thicken Now called chromatids/chromosomes Centromeres form Nuclear membrane breaks apart Spindle fibers begin to form CROSSING OVER may occur.
Metaphase I Copied chromatids / chromosomes line up in middle of cell in HOMOLOGOUS PAIRS Centromeres attach to spindle fibers
Anaphase I Homologous chromosomes separate and move to the poles. Chromatid pairs are NOT pulled apart They DO NOT separate Chromatids move to ends of cell
Telophase I May or May Not occur. If it does: Normal telophase, X-somes uncoil, nucleus appears, cell divides No further replication of hereditary material
- There are now two cells with each cell carrying only ½ the original chromosome number. (HAPLOID) - Cells carry one duplicated copy of a single chromosome. They do not normally or necessarily carry the same genetic information as the parent cell or the sister chromatid. Because the chromosome number decreases this phase of meiosis is known as Reduction Division.
Prophase II Similar to mitosis Starts with TWO cells instead of one Spindle fibers appear Nucleus disappears (if reformed)
Metaphase II Duplicated chromatid / chromosomes line up in middle of cell Spindle fibers attach to centromeres
Anaphase II Centromere divides Chromatids separate & move to ends of cell Chromatids are now individual chromosomes
Telophase II Spindle fibers disappear Nuclear membranes form at each end of cell Cells divide Results in 4 cells Each with ½ the original number of chromosomes
In summary: Meiosis Two cells form during meiosis I In meiosis II, both of these cells form two cells The two divisions of the nucleus result in four sex cells (gametes) Each has one-half the number of chromosomes in its nucleus that was in the original nucleus