CELL THEORY 1 Cells are the basic unit

CELL THEORY 1. Cells are the basic unit of life. 2. All living things are made up of one or more cells. 3. All cells come from preexisting cells.

Asexual Reproduction • Asexual Reproduction: Produces offspring identical to the parent. – EX. Budding: a type of asexual reproduction in which a cell or group of cells pinch off from the parent to form a new individual. – EX. Mitosis (Oh My toes): want the same kind of cells on your toes. • Mitosis is a type of asexual reproduction when a nucleus undergoes cell division in which two daughter cells are formed, each containing a complete set of chromosomes.

Cell Division • Two Types –Meiosis (Sexual Reproduction) • Sex Cells (Sperm or Egg) –Mitosis (Asexual Reproduction) • 2 Daughter cells (similar cells)

Cell Cycle/Cell Division Cell Cycle is the pattern of division & growth of a cell. It involves the copy & distribution of the genome (genetic information/DNA).

The cell cycle serves 3 main functions…. 1. Reproduction • In single-celled organisms, 2 separate individual organisms are the result of the cell cycle. 2. Growth & development • In multi-cellular organisms, rapid copying of cells via the cell cycle add to the growing organism. 3. Tissue & renewal • In multi-cellular organisms that have reached maximum growth, the cell cycle renews & replaces older cells to maintain and organism’s size & function.

Cell Division/Cell Cycle • Mitosis: – Mitosis (Oh My toes): want the same kind of cells on your toes. • Mitosis is a type of asexual reproduction when a nucleus undergoes cell division in which two daughter cells are formed, each containing a complete set of chromosomes.

Continue Cell Cycle • Somatic cells are all the body’s cells except the reproductive cells; egg & sperm. • Somatic cells contain 46 chromosomes. – Chromosomes are condensed chromatin into double rods (chromatids) of genetic material. » Chromatin • The mass of very long, thin fibers of DNA & proteins that are found unwound within the nucleus. » Chromatid • ½ of the double-rodded structure of a chromosome

3 Stages of Cell Division/Cell Cycle 1. Interphase (Cell is getting ready) 2. Mitosis (Cell Division-4 phases) 3. Cytokinesis (Chop/2 cells)

Interphase 1. Stage 1: Interphase (21 hours) • Interphase is the longest of the 3 stages of the Cell Cycle • The cell begins to grow & enlarge • Replication of DNA

• The primary process that takes place during Interphase is the replication of DNA. –DNA (deoxyribonucleic acid) is the sequence of nitrogen base pairs that determines the structure of proteins and serves as the genetic code of life. » Replication is the process by which the DNA makes an exact copy of itself.

• The cell produces structures that will be used to help the cell divide into 2 new cells. – Centromere connects the chromatids or double rods of chromosomes. – Centrioles are organelles used to separate & pull chromosomes into new nuclei. » Spindle fibers are bands that extend from the centriole & attach to the chromosome & pull it into separate nuclei.

Interphase

Stage 2: Mitosis • Mitosis – 4 Phases – Mitosis is the 2 nd stage of the Cell Cycle and takes <50 minutes. – During Mitosis, 2 nuclei are created and 1 copy of the DNA created during Interphase is distributed to each of the nuclei. – (Falwell) My toes…You want the same cells for skin cells, toe nails, hair etc. • Remember: Skin cells, hair cells, etc, are Somatic Cells

4 Phases of Mitosis 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

Prophase (1 st phase of Mitosis) –Prophase is the longest phase of Mitosis. –Chromatin in the nucleus condenses to form chromosomes. –Spindle fibers form a bridge between the ends of the cell. –Nuclear envelope breaks down

Prophase

Prometaphase • Recently a new phase; Prometaphase, has been added in between Prophase and Metaphase. » Centrioles move to opposite sides of the nucleus. » Kinetochore is a specialized structure located at the centromere region forms.

Metaphase –Chromosomes line up across the metaphase plate, an imaginary plane located across the center of the cell. –Each chromosome attaches to a spindle fiber at its centromere

Metaphase

Anaphase – The centromere split. – The 2 chromatids separate. – 1 chromatid is drawn by its spindle fiber to 1 end of the cell. – The other chromatid moves to the opposite end. – Cell stretches out as the opposite ends are pushed apart.

Anaphase

Telophase –Chromosomes begin to stretch out & lose their rod like appearance. –A new nuclear envelope forms around each region of chromosomes.

Telophase

The End of Mitosis

• Remember 3 stages of cell division/cell cycle – Stage 1: Interphase – Stage 2: Mitosis • Phase 1: Prophase • Phase 2: Metaphase • Phase 3: Anaphase • Phase 4: Telophase – Stage 3: Cytokinesis

Stage 3: Cytokinesis – Cytokinesis (< 15 minutes) • The cytoplasm divides. • The 1 st sign of cleavage is the appearance of a cleavage furrow. – A cleavage furrow is shallow groove in the cell surface near the old metaphase plate. • Cytokinesis actually begins during Telophase, the last phase of Mitosis. • 2 new cell membranes form around the 2 new cells. • The new cells have an identical set of chromosomes and half of the organelles

Cytokinesis