Lecture 4 - It's a Cell Life…

• • When we talk about the passing on of genes/DNA we are looking at Reproduction
• • Two types of reproduction

  1. Asexual Reproduction
  2. Sexual Reproduction
• • Asexual Reproduction ~ the production of offspring from a single parent, the genetic makeup of the offspring is identical to that of the parent.
• Asexual Reproduction

  • Advantages: parent does not have to seek out a mate, perform specialized mating behaviors or posses specialized anatomy
  • Disadvantage: all offspring are genetically the same thus no variation
• This type of replication occurs in all somatic cells ~ body cells of a plant and animal.
• • Sexual Reproduction ~ the production of offspring from the fusion of two sex cells (usually from two different parents) the genetic of the offspring will be different than the parents
• Sexual Reproduction

  • Advantages: when the environment changes the organism lives in, the genetic variability will allow the organism to adapt and evolve with the environment
  • Disadvantage: specialized organs, sexual behaviors/adaptations, and it uses a lot more energy
• Why do Cells Divide?

  1. Growth and development
  2. Tissue repair
  3. Replacement of aging cells
• Repair

  • Your body sheds millions of cells each day.
  • Red Blood Cells are replaced about every 120 days.
  • Cuts need new cells to fill gaps.
  • We need repair to stay alive!
• All Cells Need the Same Things:

  • Energy
  • Nutrients
  • Water
  • Gasses
  • Waste disposal

  These materials must travel to cells in order to be used.

  It is much more efficient to travel across smaller cells than larger ones.
• • Chemicals are needed for cell activity & growth. They can go across the membrane by diffusion.
• • Diffusion: the movement of chemicals into and out of cells from high concentration to low concentration.
• • Concentration: is the amount of substance/chemical in a solution.             
• • Osmosis: The movement of water toward an area of high solute concentration.
• • Water enters and leaves cells by osmosis.
  • Example: Sugar Solute
• The process of determining the exact order of nitrogenous bases is called DNA sequencing. In July 2000, the 2 major American labs working on the Human Genome Project (HGP) announced that 99% of our genes had been sequenced.