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Learn about mitosis, the process of cell division that produces two identical daughter cells. Explore the stages of the cell cycle, regulation mechanisms, ploidy, and chromosome characteristics. Discover the phases of mitosis like prophase, metaphase, anaphase, and telophase, as well as cytokinesis in both animal and plant cells. Understand how mitosis is crucial for asexual reproduction and the types of asexual reproduction methods.
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What is Mitosis? • Division of the nucleus plus division of the cell itself (cytokinesis) • Produces two identical daughter cells during prophase, metaphase, anaphase, and telophase.
Stages of the cell cycle • An ordered set of events, culminating in cell growth and division into two daughter cells. • Non-dividing cells not considered to be in the cell cycle.
Stages of the cell cycle • INTERPHASE • G1 stage = "GAP 1” cell growth • Sstage = "Synthesis” • DNA replication • G2 stage = "GAP 2” organelle production • MITOSIS • M phase = nucleus divides • CYTOKINESIS • cytoplasm divides daughter cells
Regulation of the Cell Cycle • Very complex • Errors can lead to cancer. • In cancer, regulation of the cell cycle goes awry • Normal cell growth & behavior is lost.
Ploidy • Number of sets of chromosomes in a cell • Haploid (n)-- one set chromosomes • Diploid (2n)-- two sets chromosomes • Most plant and animal adults are diploid (2n) • Eggs and sperm are haploid (n)
Chromosome Characteristics • Diploid set for humans; 2n = 46 • Autosomes = body chromosomes • Female-sex chromosomes = homologous (XX) • Male-sex chromosomes = non-homologous (XY)
Interphase • The cell is metabolizing, growing and preparing for mitosis
Interphase • Chromosomes are not clearly seen • Nucleolus may be visible • In animal cells ONLY, a pair of centrioles may start moving into position.
Prophase • Chromatin begins to condense and becomes visible. • Nucleolus disappears. • Centrioles begin moving to opposite ends of the cell
Prophase (con’t) • Nuclear membrane dissolves • Microtubules attach and chromosomes begin moving.
Metaphase • Spindle fibers align the chromosomes along metaphase plate. • Helps to ensure each new nucleus will receive one copy of each chromosome.
Anaphase • Paired chromosomes separate and move to opposite sides
Telophase • Chromatids arrive at opposite poles • Membranes re-form around daughter nuclei. • Chromosomes & spindles disperse and are no longer visible. • Cytokinesis may begin
Cytokinesis: Animals • Fiber ring of protein called actin around center of cell contracts • Pinches cell into two daughter cells
Plants • In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.
Asexual Reproduction • Uses only mitosis • Cells duplicate to form 2 exact copies (clones) of each other • Most primitive form of reproduction • NO GENETIC VARIATION • Used by higher organisms when conditions are not favorable for sexual reproduction
Types of Asexual Reprod. • Binary fission • Budding • Fragmentation • Regeneration • Spore formation • Parthenogenesis