Lesson Overview Lesson Overview The Process of Cell Division The Process of Cell Division & Mitosis -Distinguish between sexual and asexual reproduction -Describe the role of chromosomes in cell division. -Name the main events of the cell cycle. -Describe what happens during the four phases of mitosis. -Describe the process of cytokinesis.

Lesson Overview Lesson Overview The Process of Cell Division Comparing Sexual and Asexual Reproduction

Lesson Overview Lesson Overview The Process of Cell Division Asexual reproduction involves a single parent producing an offspring. The offspring produced are, in most cases, genetically identical to their parent cell. Asexual Reproduction

Lesson Overview Lesson Overview The Process of Cell Division Sexual Reproduction In sexual reproduction, offspring are produced by the fusion of two sex cells – one from each of two parents. These fuse into a single cell before the offspring can grow. The offspring inherits some genetic information from both parents.

Lesson Overview Lesson Overview The Process of Cell Division The genetic information is carried by chromosomes. Every cell must copy its genetic information before cell division begins. Cells of every organism have a specific number of chromosomes. Humans have 46 chromosomes (or 23 pairs). Chromosomes

Lesson Overview Lesson Overview The Process of Cell Division Prokaryotic Chromosomes Prokaryotic cells lack nuclei. Their DNA molecules are in the cytoplasm. Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains the cell’s genetic information.

Lesson Overview Lesson Overview The Process of Cell Division Eukaryotic Chromosomes In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin. Chromatin is composed of DNA and histones. The DNA supercoils around the histones (a type of protein).

Lesson Overview Lesson Overview The Process of Cell Division The Prokaryotic Cell Cycle P rokaryotic cells begin to replicate, or copy, their DNA once they have grown to a certain size. When DNA replication is complete, the cells divide through a process known as binary fission. Binary fission is a form of asexual reproduction.

Lesson Overview Lesson Overview The Process of Cell Division The Phases of the Eukaryotic Cell Cycle: 1. Growth/Gap 1 (G1) - cell grows & carries out life functions. 2. Synthesis (S)* – DNA is copied. 3. Growth/Gap 2 (G2)* – cell continues growth preparing for mitosis. *Interphase is the time between cell divisions. It consists of the G1, S and G2 phases. LONGEST STEP IN THE CELL CYCLE! 4. Mitosis (M) – division of the nucleus. 5. Cytokinesis (C) – division of the cytoplasm.

Lesson Overview Lesson Overview The Process of Cell Division Prophase During prophase the duplicated chromosome become visible. The nuclear envelope breaks down. * Longest stage of mitosis

Lesson Overview Lesson Overview The Process of Cell Division Metaphase During metaphase the chromosomes line up in the middle of the cell. The spindle fibers connect to the centromere of each chromosome.

Lesson Overview Lesson Overview The Process of Cell Division Anaphase During anaphase the centromeres are pulled apart and the chromatids separate into two groups near each pole. *Shortest stage of mitosis.

Lesson Overview Lesson Overview The Process of Cell Division Telophase During telophase the chromosomes spread out. A nuclear envelope re- forms around each cluster of chromosomes. The spindle breaks apart.

Lesson Overview Lesson Overview The Process of Cell Division Cytokinesis is the division of the cytoplasm. The process of cytokinesis is different in animal and plant cells. Cytokinesis

Lesson Overview Lesson Overview The Process of Cell Division Cytokinesis in Animal Cells The cell membrane is drawn in until the cytoplasm is pinched into two equal parts.

Lesson Overview Lesson Overview The Process of Cell Division Cytokinesis in Plant Cells In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall. Instead, a cell plate forms between the divided nuclei.