The Tragic Ending

Cell Division in Eukaryotes As you are sitting in class now, your cells are growing, dividing and dying. Cuts and bruises are healing RBC’s are being produced in your bones at a rate of million per sec. Muscle cells are get larger when you exercise. Worn out cells in the palm of your hand are being replaced.

Cell Division How do you grow? The number of cells in your body is increasing!!

How Do Cells Increase In Number? In your body, all of your cells, except your sex cells, divide by a process called mitosis. In mitosis, a parent cell divides to form two identical daughter cells. The daughter cells have the same contents of the parent’s nucleus.

Cell Cycle Most of a eukaryotic cell’s life is spent in a phase called interphase. Interphase consists of three stages: G1, S, and G2 –G1: a time of growth and maintenance –S: DNA is replicated: this commits the cell to divide –G2: more growth as the cell prepares for division.

Cell Cycle Mitosis: division of the nucleus: –Four phases: prophase, metaphase, anaphase and telephase. Cytokinesis: division of the cytoplasm After the cell divides into 2 identical daughter cells, the cycle starts over again.

Cell Cycle

Interphase Chromatin coils up into chromosomes A copy of each chromosome in the nucleus is produced These duplicated chromosomes are held together by a centromere. Cells that no longer divide are always in interphase.

Interphase

Mitosis in Animal Cells A form of asexual reproduction The nucleus of a cell divides, producing 2 nuclei that are identical to each other Has 4 phases: prophase, metaphase, anaphase, telophase

Prophase Duplicated chromosomes become fully visible Organelles called centrioles move to opposite ends of the cell The nucleolus and nuclear membrane disintegrate Threadlike spindles stretch across the cell between the centrioles

Prophase

Metaphase Duplicated chromosomes line up across the center, or equator, of the cell. Each centromere attaches to 2 spindle fibers

Metaphase

Anaphase Each centromere splits and the identical chromosomes separate and move towards opposite ends of the cell.

Anaphase

Telophase Spindle fibers disappear Chromosomes uncoil and are harder to see A nuclear membrane forms around each mass of chromosomes A new nucleolus forms in each new nucleus

Telophase

Cytokinesis The cytoplasm and its contents divide into 2 individual daughter cells. Each daughter contains a nucleus and identical chromosomes.

Virtual Lab Cell Reproduction 1.htmlhttp://bio.rutgers.edu/~gb101/virtuallabs_10 1.html

Mitosis in Plant Cells What’s Different? Plant Cells do not have centrioles A cell plate forms between 2 new nuclei New cell walls form along the cell plate, and new cell membranes form inside the cell walls.

Plant Mitosis

"And do you, Michelle, take Andrew until mitosis do you part?"

Chromosomes - The other two chromosomes, X and Y, are the sex chromosomes. The above picture of the human chromosomes lined up in pairs is called a karyotype. -The 22 autosomes are numbered by size.