Three reasons why cells reproduce by asexual reproduction

Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly.

Animated Mitosis Cycle http: //www. cellsalive. com/mitosis. htm • Interphase • Prophase • Metaphase • Anaphase • Telophase & Cytokinesis

Interphase occurs before mitosis begins • Cell is doing all other activities (growth, specilalized functions) • Chromosomes (we have 46 of them) appear as threadlike coils (chromatin) at the start, the chromatin is copied (duplicated – so there are 92) to prepare for cell division • Other organelles are also copied • Centrioles are copied Centrioles Nucleus CELL MEMBRANE Cytoplasm

Interphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Prophase • Chromatin thickens/condenses into chromosomes • Each chromosome (because it was copied already) consists of 2 identical stands called sister chromatid • These are held together by a centrometre • The nuclear membrane dissolves • Centrioles (or poles) begin to move to opposite end of the cell. • Spindle fibers form between the poles. Sister chromatids Centrioles Spindle fibers

Prophase Animal Cell Plant Cell Spindle fibers Centrioles Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Metaphase • Chromatids (or pairs of chromosomes) attach to the spindle fibers. • Chromosomes line up in the middle plane of the cell Centrioles Spindle fibers

Metaphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Anaphase • Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell by being pulled by the spindle fibers contracting to the centrioles • The split sister chromatids are called daughter chromosomes Centrioles Spindle fibers

Anaphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Telophase • Two new nuclei (nuclear membranes) form around the daughter chromosomes. • Chromosomes appear as chromatin (threads rather than rods). • Mitosis ends. Nuclei Chromatin Nuclei

Telophase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Cytokinesis occurs after mitosis • Cell membrane moves inward (is pinched) to create two daughter cells – each with its own nucleus with identical chromosomes in an animal cell • In a plant cell, a new cell wall forms and divides into two daughter cells.

Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase

Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase

Cell Cycle 16