Mutation and Meiosis as a Source of Variation

• Inheritance of Mutation


  A mutation will only be inherited by future offspring, if it occurs in a gametic cell. Mutations that occur in somatic cells will not be inherited by future offspring.

  
  

  Somatic cell = Body cell (skin cells, muscle cells etc.)

  Gametic cell = Gametes (egg and sperm cells)

  
• Types of Mutation

  A) Somatic

  B) Gametic

  
• Effect of Mutations

  1. Neutral or Silent - No observable effect on the individual
  2. Harmful mutation - May affect the survival of the individual
  3. Beneficial - Gives the individual a survival advantage
• Meiosis as a Source of Variation

  It is a type of cell division that is used to produce male and female gametes.

  
  

  Gamete = sex cell (egg or sperm)

  
  

  A gamete has half as many chromosomes as a body cell. In humans, body cells contain 46 chromosomes, and gametes only have 23 chromosomes.
• Meiosis as a Source of Variation

  A) chromosome

  B) replicated chromosome

  C) identical sister chromatids

  D) homologous chromosomes

  E) non-identical sister chromatids

  
• The Steps in Meiosis(Part 1)

  Interphase - normal cell function & DNA replication

  1. DNA Replication occurs
  2. Homologous chromosomes pairs up
  3. Crossing over occurs
  4. Homologous pairs of chromosomes line up at the cell equator through independent assortment and spindle fibers form
  5. Spindle fibers pulls apart the homologous chromosomes
  6. First cell division and cytokinesis occurs, producing two cells
• The Steps in Meiosis (Part 2)

  7. New spindle fibers form in each cell and chromosomes line up in single file at the cell equator

  8. Chromatids are pulled apart to the poles of the cell through segregation

  9. Second cell division occurs, forming four genetically unique daughter cells