1. Genes and Cell Division Genes and the Cell Cycle Mr. Walker Biology

2. Obj 1: Function of Genes
Genes are composed of DNA which is the instructions on how to build a protein.
Regions of DNA which codes for proteins are called Exons.
Regions of DNA which do not code for proteins are called Introns.
Genes are used by organisms to build proteins like enzymes, antibodies, and hormones etc.

3. Obj 2: Composition of Chromosomes
Eukaryote cells divide a complicated system called Mitosis
This is because:
They have a nucleus which must be broken up and then reformed
They have their DNA “packaged” in the form of Chromosomes
Chromosomes are composed of Chromatin
-Made of DNA Strands & Proteins
Also contain Nucleosomes consisting of Histones – Proteins.
DNA wrapped around for the DNA/Protein complex is Chromatin
They usually have more than 1 chromosome (Humans have 23 pairs)
They have numerous organelles to equally share

4. Different levels of DNA condensation. (1) Single DNA strand
Different levels of DNA condensation. (1) Single DNA strand. (2) Chromatin strand (DNA with histones). (3) Chromatin during interphase with centromere. (4) Condensed chromatin during prophase. (Two copies of the DNA molecule are now present) (5) Chromosome during metaphase.

5. Chromatin / Chromosomes

6. The Cell Cycle
Most of the cell's life is spent doing its regular function.
Cells divide along a rough time frame called its Cell Cycle.
The Cell cycle consists of the following steps:
G1 (Gap 1) Phase - Cell performs its normal function (cells which do not divide stay in this stage for their entire life span)
S (Synthesis) Phase - Here the cell actively duplicates its DNA in preparation for division
G2 (Gap 2) Phase - Amount of cytoplasm (including organelles) increases in preparation for division.
Mitosis - Actual division occurs

7. Chromosome vs Sister Chromatid

8. Interphase
Cell Replicates its DNA/Chromosomes in preparation of upcoming division
Animal Cell
Plant cell

9. Prophase 1.Chromosomes Shorten and become visible.
2. Centrioles move to opposite sides of the cell
3. Nuclear envelope disappears
4. Spindle Fibers both together are known as the Spindle Apparatus begin to form
Animal Cell
Plant Cell

10. Metaphase
Chromosomes line up along center of cell called the Metaphase Plate
Chromosomes attach to spindle fibers
Spindle fibers are now clearly visible
Animal Cell
Plant Cell

11. Anaphase Centromeres break up separating chromosome copies
Chromosomes are pulled apart to opposite sides of cell
Spindle fibers begin to break down
Animal Cell
Plant Cell

12. Telophase (cytokenesis)
Nuclear envelope forms around both sets of chromosomes
DNA uncoils
Spindle & Astral fibers completely disappear
Cytokenesis happens with most (but not all) cells
Cytoplasm & organelles move (mostly equally) to either side of the cell.Cell Membrane “pinches” to form 2 separate cells
Animal Cell
Plant
Cell

13. Animal Cytokeneisis
Cytokenesis differs significantly between Animal & Plant cells.
With animals, the membranes pinch together to form a Cleavage Furrow, which eventually fuses to form two daughter cells

14. Plant Cytokenesis
With Plants, a cell wall must be formed between the 2 daughter cells.
Vessicles containing Cellulose form and fuse between the two daughter cells (called a cell plate), eventually forming a complete cell wall.

15. Overview of Mitosis