Lesson Objectives—Cell Cycle Describe cell division in eukaryotes. Describe the basic properties of chromosomes. Describe the key steps in the cell cycle. Identify and describe the main processes in mitosis. .

Cell Division Process by which a cell divides to form new cells (daughter cells) Three types of cell division Prokaryotes (bacteria) Binary fission: divides forming two new identical cells, faster than mitosis, 20 minutes, no involvement of the nuclear envelope and centromeres Eukaryotes Mitosis Body Cells: Somatic cells; Diploid (2n): homologous pair;2 X 23 Chromosomes = 46 chromosomes; 1 cell to 2 cells, exact copy Meiosis Sex Cells: Meiosis; gamete cells; haploid; 1n; 1 X 23 Chromosomes = 23 chromosomes, 1 cell to 4 cells; not identical variability

Cell Division where multiplication and divide mean the same thing!

Why do cells divide? So an organism can grow Replace dead or worn out cells Repair cells

The core macromolecule of mitosis DNA (Deoxyribonucleic Acid): genetic material of nearly all organisms Chromosomes: DNA in a coiled, rod shaped form that occurs during cell division

Cell Cycle of Body Cells Cell cycle is continuous process 1) Cells grow 2) DNA replicated 3) Organelles duplicated 4) Divide to form daughter cells 1: Interphase: (3 Phases; G1, S, G2) ; Period of growth and DNA replication ; 2: Mitosis (4 steps; Prophase, Metaphase, Anaphase, Telophase) Nucleus divides 3: Cytokinesis—Cytoplasm divide, forming 2 cells; each new daughter cell is genetically identical to parent cell  

Cell Cycle of Body Cells interphase Interphase: period of growth and DNA replication between cell divisions Three phases: G1 Phase, Also *Check point Cell increases in size , DNA is in chromatin form (thread like coils) S Phase, Also *Check point Replication of chromosomes Now two strands called sister chromatids joined by a centromere G2 Phase, Also* Check point organelles double new cytoplasm forms All other structures needed for mitosis form *A checkpoint is a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and "decides" whether or not to move forward with division. *Once the cell passes the G1 checkpoint and enters S phase, it becomes irreversibly committed to division.

Cell Cycle of Body Cells G1 phase M phase S phase G2 phase

PMAT Mitosis (1)Prophase (2)Metaphase (3)Anaphase (4)Telophase Process that divides cell nucleus to produce two new nuclei each with a complete set of chromosomes Continuous process 4 Phases (1)Prophase (2)Metaphase (3)Anaphase (4)Telophase PMAT

Prophase 1. Chromosomes visible (sister chromatids) 2. Centrioles migrate to the poles (only in animals) 3. Nuclear membrane disappears 4. Spindle forms

Metaphase chromosomes line up on the equator of the cell spindles attach to centromeres

Anaphase sister chromatids separate centromeres divide sister chromatids move to opposite poles

Telophase 1. chromosomes uncoil • now chromatin 2. nuclear membranes reform 3. spindle disappears

Cytokinesis Occurs at end of Mitosis --division of the cytoplasm to form 2 new daughter cells --organelles are divided -Daughter cells are genetically identical

Warm-up

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Cell Cycle- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Cell Cycle Plants Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Mitosis Activities Finish mitosis presentation Start mitosis flip-book

Mitosis Name the phases starting at the top

Name the phase Identify X Identify Y

6. Name the phase

. Name the Phase

Control of the Cell Cycle Regulatory proteins called cyclins control the cell cycle at checkpoints: G1 Checkpoint—decides whether or not cell will divide S Checkpoint—determines if DNA has been properly replicated Mitotic Spindle Checkpoint—ensures chromosomes are aligned at mitotic plate

Cell Cycle Checkpoints

CANCER CELLS Result of uncontrolled cell division of cells that have lost ability to regulate cell cycle Reproduce more rapidly than normal cells Masses formed called ‘tumors’ Can be caused by: Cell’s DNA is damaged Radiation Toxic chemicals May form a tumor (mass of abnormal cells)

Lesson Summary—Cell Cycle The cell cycle is a repeating series of events, characterizing the life of a eukaryotic cell. Binary fission is a form of cell division in prokaryotic organisms that produces identical offspring. As a eukaryotic cell prepares to divide, the DNA and associated proteins coil into a structure, known as a chromosome. The DNA copies during the S phase of the cell cycle, resulting in a chromosome that consists of two identical chromatids, known as sister chromatids, attached at a region called the centromere. Any cell containing two sets of chromosomes is said to be diploid; the zygote forms from the fusion of two haploid gametes. The cell cycle has five phases: the first growth (G1) phase, the synthesis (S) phase, the second growth (G2) phase, mitosis, and cytokinesis. Mitosis is the division of the nucleus; four distinct phases of mitosis have been recognized: prophase, metaphase, anaphase, and telophase. Cytokinesis is the division of the cytoplasm. The cell cycle is controlled through feedback mechanisms. Cancer results from uncontrolled cell division, due to the loss of regulation of the cell cycle.