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.