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This chapter explores cell division in prokaryotes and eukaryotes, focusing on chromosomes, replication processes, and the phases of mitosis. Learn about the differences between prokaryotic binary fission and eukaryotic mitosis in detail.
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Chapter 10 Cell Division
Prokaryotic Division • Chromosomes (colored bodies) • Prokaryotes have a single, circular chromosome
Prokaryotics • Cell Division • Prokaryotes (bacteria) reproduce through cell division • Binary fission • Circular chromosome (DNA) is replicated • Replicated chromosomes are attached to the cell membrane at nearby sites • As membrane expands, the copies separate • New cell wall forms between copies, cell splits
What about eukaryotic division? • Mitosis • Eukaryotes use cell division to create new cells • MITOSIS: division of the nucleus • Growth, Maintenance and Repair • Asexual cell division • Reproduction • MEIOSIS: a special, two-stage type of mitosis that results in daughter cells with half as many chromosomes as the parent cells
Humans • 46 chromosomes • Diploid state (2n = 46) • 2 sets of 23 chromosomes (diploid) • n = number of chromosomes in a set • Fundamental number, haploid number • In humans 23 • n = contribution from each parent • #23 = 1 sex chromosome, #1-22 autosomes
Chromosomes • Maternal PaternalSex: X or X X or Y Autosomes #: 1 1 2 2 ä ä 22 22(homologous pairs)
The Cell Cycle The Cell Cycle shows the stages of life of a cell
Cellular Division Cell division is how a cell makes a copy itself A cell spends most of its life in interphase 1st stage = G1, a growth phase; the number of organelles and the amount of cytoplasm double 2nd stage = S phase; DNA replicates (the chromatins turn into chromosomes) chromatins – loose uncoiled strands of DNA chromosomes – DNA wrapped around proteins How does DNA replicate? DNA Replication 3rd stage = G2, another growth phase; the cell will continue to grow
Cellular Division After interphase, the cell goes through mitosis Mitosis is the next 4 phases of cellular division Mitosis occurs in all eukaryotic cells Only in your somatic cells Eukaryotic cells are cells that have a nuclei and membrane bound organelle Somatic cells are all body cells except for egg cells and sperm cells
Phases of Mitosis First Phase – Prophase What happens during prophase? 1. Chromosomes condensed - become thicker 2. The nucleolus and nuclear membrane break down and disappear 3. Centrioles move to opposite sides of the cell 4. Spindle Fibers appear and radiate from the centrioles Spindle fibers are protein tubes
Phases of Mitosis Second Phase – Metaphase What happens during metaphase? 1. Chromosomes move to the middle of the cell 2. Spindle fibers are attached to the chromosomes controlling their movement
Phases of Mitosis Third Phase – Anaphase What happens during anaphase? 1. The centromere breaks down The centomere holds the chromosomes together 2. The spindle fibers pull apart the chromosome Separating the sister chromatids
Phases of Mitosis Fourth Phase – Telophase What happens in telophase? 1. Nuclear membrane forms around chromatids This Forms a nucleus with a nucleolus 2. Chromatids turn into chromatins 3. The cell membrane starts to pinch inward to separate into 2 new cells 4. Centrioles and spindle fibers disappear
Phases of Mitosis Cytokinesis is the last stage of cell division During cytokinesis the 2 cells actual split apart from each other In a plant cells, a cell plate grows between to the two new cell The cell plate develops into the cell wall