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Explore the fundamental aspects of cell division processes - mitosis and meiosis, chromosomes, and the crucial role they play in the life cycle. Understand the intricate structures and stages in eukaryotic cell cycles with clear explanations and visuals. Discover the significance of genetic inheritance and how cells divide to ensure continuity and variability in offspring.
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Cells • Basic unit of life • Essential link between generations • Genomes • Even simplest cell contains DNA, collectively called the organism’s genome • Organized into genes
Prokaryotic cells • Circular DNA molecules • Eukaryotic cells • Chromosome packaging facilitated by histones • Histones form nucleosomes • Scaffolding proteins maintain chromosome structure
Eukaryotic cell cycle • Beginning of one division to beginning of next • Stages in eukaryotic cell cycle • Interphase • First gap phase • Synthesis phase • Second gap phase • M phase • Mitosis • Cytokinesis
Structure of duplicated chromosome • Pair of sister chromatids • Contain identical DNA sequences • Tightly associated in region of centromeres • Each chromatid • Includes region called centromere • Kinetochore attached to each centromere
Mitosis • Identical chromosomes distributed to each cell pole and a nuclear envelope forms • Stages • Prophase • Metaphase • Anaphase • Telophase
Stages of Mitosis
Asexual reproduction • Offspring have hereditary traits identical to single parent • Mitosis is basis • Sexual reproduction • Gametes fuse to form a zygote • Meiosis is basis
Diploid cells • Characteristic number of chromosome pairs per cell • Homologous chromosomes • Similar in length, shape, other features, and carry similar attributes • Haploid cells • Contain only one member of each homologous chromosome pair
Meiosis • Diploid cell undergoing meiosis yields four haploid cells
Mitosis Prophase Anaphase Daughter cells Meiosis Prophase I Anaphase I Prophase II Anaphase II Haploid cells Mitosis vs. Meiosis
Roles of mitosis and meiosis in various life cycles • Many simple eukaryotes remain haploid • In sexual life cycle, meiosis occurs before gametes form • Plants, some algae, and some fungi have complex life cycles with alternation of generations