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Chapter 8 Cellular Reproduction Flashcards
Chapter 8 Cellular Reproduction Flashcards
Basics of Cellular Reproduction
Multicellular organisms originate from a single cell and grow through cellular reproduction.
Cellular reproduction replaces worn-out or damaged tissues.
Important Processes
Growth: Cell duplicates its contents, including DNA and organelles.
Cell division: Parent cell divides into two daughter cells.
Both processes are heavily regulated.
Asexual Reproduction
All cells come from pre-existing cells.
Reproduction occurs without sperm and egg.
Examples:
Bacteria reproduce via binary fission.
California blackworm reproduces by fragmentation.
Binary Fission in Bacteria
Prokaryotes (bacteria and archaea) reproduce through binary fission.
Chromosome/DNA replicates, and daughter chromosomes move apart.
Plasma membrane pinches inward, dividing the cell into two.
Cell Reproduction in Eukaryotes
More complex than in prokaryotes.
Eukaryotes have more DNA.
DNA is wrapped around proteins, forming chromosomes.
DNA replication copies DNA, passing a full set to each daughter cell.
Chromosomes
DNA packaged into a thickened complex of DNA and protein.
Allows easier distribution to daughter cells.
Chromatin: DNA and associated proteins in thin threads.
Sister chromatids: Identical DNA copies joined at the centromere.
Chromosome Compaction
DNA winds around histones to form nucleosomes.
Chromatin condenses into chromosomes before cell division.
Humans have 46 chromosomes.
Duplicated chromosomes consist of sister chromatids joined at the centromere; each has identical DNA.
Cell Cycle: Interphase, Mitosis, and Cytokinesis
Cell cycle: Orderly sequence of stages from a new cell to its division into two daughter cells.
Consists of interphase and M (mitotic) phase.
Cell Cycle Stages
Mitotic (M) phase: Mitosis and cytokinesis.
Interphase: Cell growth and chromosome copying for cell division.
Interphase
Majority of the cell cycle; cell performs usual functions.
Length varies widely.
Stages: G1, S (DNA synthesis), G2.
Interphase Stages
G1: Cell doubles organelles, accumulates materials for DNA synthesis, decides whether to divide (G0 is arrested).
S: DNA synthesis results in chromosomes with two sister chromatids.
G2: Proteins are synthesized for cell division.
M (Mitotic) Phase
Division of nucleus (mitosis) into two genetically identical daughter nuclei.
Followed by division of cytoplasm (cytokinesis).
Mitosis
Division of one nucleus into two genetically identical nuclei.
Conventionally divided into prophase, metaphase, anaphase, telophase.
Cytokinesis overlaps latter stages of mitosis.
M (Mitotic) Phase Details
Distributes duplicated nuclear contents equally to daughter cells.
Daughter chromosomes are separated sister chromatids.
Mitosis Outcomes
Daughter nuclei are genetically identical to each other and to the parent nucleus.
Spindle
Eukaryotic cells use this structure to pull chromatids apart.
Part of the cytoskeleton; spindle fibers are microtubules.
Centrosome: primary microtubule organizing center.
Mitosis Phases
Traditionally divided into four phases based on chromosome changes and movement:
Prophase
Metaphase
Anaphase
Telophase
Followed by cytokinesis (division of cytoplasm).
Cytokinesis in Animal Cells
Cleavage furrow forms as anaphase ends.
Contractile ring (actin filaments) creates a constriction.
Cytokinesis Process
Occurs via cleavage, forming a cleavage furrow.
Contractile ring of actin microfilaments and myosin contracts.
Cleavage furrow deepens until parent cell is pinched in two.
Mitosis Differences
Plant cells: Spindle fibers but no clearly visible centrosome.
Animal cells: Each centrosome has 2 centrioles and an aster.
Cytokinesis in Plant Cells
Rigid cell wall prevents furrowing.
New plasma membrane and cell walls are built between daughter cells.
Golgi apparatus produces vesicles.
Cell plate forms; new membrane releases molecules for new cell walls.
Plant Cell Cytokinesis Details
Cell plate forms during cytokinesis.
Vesicles from Golgi move along microtubules to the middle of the cell.
They coalesce, forming a cell plate.
Cell wall material is carried in vesicles and collects at the plate.
The cell plate enlarges until its membrane fuses with the plasma membrane.
Cytokinesis Overview
Accompanies mitosis in most cells.
Mitosis without cytokinesis results in multinucleated cells.
Mitosis Summary
Occurs in somatic cells.
Used for growth, repair, and embryonic development.
Produces two genetically identical daughter cells.
Maintains the chromosomal number of the cell (diploid number).
Mitosis vs. Meiosis Differences
Mitosis: One round of nuclear division, no synapsis or crossover events, duplicated chromosomes separate, maintains chromosome number.
Meiosis: Two rounds of nuclear division, synapsis and crossover occur, reduces chromosome number.
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