1. The Nucleus Katie Thompson

2. History of Nucleus  In 1911 Earnest Rutherford discovered a nucleus in an atom  Experimented by shooting X-rays that contained positively charged alpha particles at gold foil  The X-rays were shot through the middle of an atom and bounced back demonstrating a densely populated area of other positive particles  This disproved the Plum Pudding Model and brought the modern model of the atom with scattered electrons and a positively charged nucleus

4. Definition Physics  A positively charged central core of an atom, consisting of protons, neutrons, and nearly all its mass. Biology  Dense organelle present in most eukaryotic cells, typically a single rounded structure bounded by a double membrane, containing genetic material.

5. Structure  The Nucleus includes: –Nuclear Envelope –Nucleolus –Nucleoplasm –Pores

6. Nuclear Envelope  Consists of two membranes enclosed in space  Surrounds nucleus  Is traversed by nuclear pores  Controls movement of molecules Nucleolus  Produces ribosomal RNA Nucleoplasm Pores  membrane-bound channels  60-90 nm diameter  Regulate passage of substances  Vary in number according to cell’s function and stage of development  Liquid inside nucleus  helps maintain shape and structure

7. Function  The function of the Nucleus is to regulate all cell activity and contains information for the production of protein within DNA  Controls heredity characteristics  Responsible for protein synthesis, cell division, growth, and differentiation

8. Replication  The nucleus divides during Mitosis and Meiosis  Mitosis: Involves the replication of all eukaryotic cells except sex cells  Meiosis: Replication of only sex cells

9. Significance  The nucleus is important to cells because…  Cell reproduction  Control metabolism  Allows genetic traits to be passed down  Instructs and initiates protein synthesis

10. Interesting Facts  Humans have 2 pairs of 23 chromosomes making up 46 chromosomes in the nucleus  The nucleus is the largest cellular organelle in animals  From a light microscope the nucleus can appear as a black dot  It's impermeable to most molecules  Usually contains up to 2 meters of DNA