Unit 8: Cell Cycle & Mitosis How do baby elephants grow up to be BIG elephants? Why do animals shed their skin?

CELL REPRODUCTION Cells make more cells by growing and dividing millions of times a day!! Two types of cell reproduction: Asexual Sexual Two types of cell division: Mitosis Meiosis

ASEXUAL VS. SEXUAL REPRODUCTION One parent Offspring are clones!! Sexual: Two parents Offspring resemble both parents!

3 REASONS WHY CELLS REPRODUCE BY ASEXUAL REPRODUCTION (MITOSIS) GROWTH REPAIR REPLACEMENT Cells that reproduce by mitosis reproduce constantly and are called somatic cells!! Body Cells

Before a cell can divide it needs instructions!!! GENETIC MATERIAL - DNA Before a cell can divide it needs instructions!!!

CHROMOSOMES In Humans… Somatic Cells: 46 chromosomes (diploid) Reproductive Cells: 23 chromosomes (haploid)

Cell Division/Cell Cycle CELL DIVISION OCCURS IN A SERIES OF STAGES, OR PHASES: Interphase Prophase Metaphase Anaphase Telophase & Cytokinesis Mitosis

INTERPHASE Cell grows!!! Copies genetic material (DNA) and other cell organelles

Gap 1 (G1) 1st Growth Stage Cells make cytoplasm and organelles Cells perform normal duties Cells grow RAPIDLY Most remain here most of their life.

Synthesis (S) DNA is copied or replicated. At the end: each chromosome consists of 2 chromatids attached at the centromere.

Gap 2 (G2) 2nd Growth Stage Cell division structures are made Centrioles – move chromosomes during mitosis Organelles & proteins are synthesized PREP for nucleus to divide

PROPHASE Genetic material condenses (shrinks!) to form chromosomes Mitosis Begins!! Genetic material condenses (shrinks!) to form chromosomes Nuclear membrane dissolves Centrioles move to opposite poles Spindle fibers form

METAPHASE Chromosomes line up in the middle of cell Meta = Middle! Chromosomes line up in the middle of cell Spindle fibers are attached!!

ANAPHASE Chromosomes are pulled apart and chromatids move to opposite ends of the cell by the spindle fibers.

TELOPHASE Chromatids relax Nuclear membranes form around chromatids Spindle fibers fall apart

CYTOKINESIS “Division of Cytoplasm” Cleavage Furrow forms in animal cells – pinching inwards by tiny filaments. Cell Plate forms in plants cells – forms in-between the two nuclei

RESULTS!!! Two daughter cells that are identical to the original cell. Video Clip