LESSON 3: MITOSIS

• gene expression - production of a protein from the information contained in DNA

  • involves transcription (making a copy of a gene) and translation (converting that copied information into a protein
• transcription - process by which DNA is copied (transcribed) to mRNA, which carries the information needed for protein synthesis

  • first step in gene expression
  • takes place in the nucleus
• translation - synthesis of proteins based on the information in mRNA

  • the mRNA formed in transcription is transported out of the nucleus, into the cytoplasm, to the ribosome (cell's protein synthesis factory)
• cell life cycle

  1. interphase
  2. cell division
• cell division - formation of 2 daughter cells from a single parent cell
• types of cell division

  1. mitosis - new cells necessary for growth and tissue repair are formed
  2. meiosis - sex cells are necessary for reproduction are formed
• mitosis - cell division that occurs in all cells except sex cells

  • a parent cell divides to form two daughter cells with the same amount and type of DNA as the parent cell (diploid)
• parts of a chromosome

  1. chromatid - two genetically identical strands of chromatin
  2. centromere - region on a chromosome that joins two sister chromatids
  3. centriole - forms spindle fibers to separate chromosomes during cell division
  4. kinetochore - a specialized region on the centromeres of chromosomes
• cytokinesis - cytoplasmic division of a cell, bringing about the separation into 2 daughter cells
• prophase

  
• prophase - chromosomes condense and become visible

  • nuclear membrane breaks down
  • centrioles move to opposite poles of the cell and the mitotic spindle forms
• metaphase

  
• metaphase - chromosomes are moved to the equator (metaphase plate) and are now attached to a pair of spindle fibers
• anaphase

  
• anaphase - sister chromatids separate and are moved towards opposite poles of the spindle by the spindle fibers (microtubules)

  • by the end, cleavage or pinching in is evident (cytoplasm begins to divide)
• telophase

  
• telophase - chromosomes disperse, the nuclear membrane and the nucleoli reform, and the spindle disappears

  • cytoplasm continues to divide to form two cells