cell division

Cards (53)

  • Mitosis
    Type of cell division used for growth and repair and asexual production
  • How does mitosis and meiosis differ?
    - Meiosis has two rounds of genetic separation and cellular division while mitosis only has one of each.
    - In meiosis homologous chromosomes separate leading to daughter cells that are not genetically identical.
    - in meiosis the cell are genetically different from parent cells, they contain half the number of chromosomes
  • Name the stages of mitosis
    - interphase
    - prophase
    - metaphase
    - anaphase
    - telophase
    - cytokinesis
  • The three group phases in interphase
    G1 phase = cell grow, bigger and replicated organelles
    S phase = cell replicates DNA
    G2 phase = cell keeps growing until all organelles have duplicated
  • once the DNA has replicated, each ________________ now consist of two sister ______________ connected by structure called _____________
    chromosome
    chromatids
    centromere
  • Function of mitochondria and ribosome in cell division
    Mitochondria produces ATP for energy
    Ribosomes, synthesises high level of proteins to replicate organelles
  • Prophase
    - chromosomes condense
    - Nuclear envelope disintegrates
    - Centrioles move to opposite poles of the cell, and form spindle fibres.
  • Metaphase
    - chromosomes line along the middle of the cell.
    - Attached to spindle fibres by their centromeres
  • Anaphase
    - centromere split
    - chromatids pull to opposite poles of cell
  • Telophase and Cytokinesis
    - chromosomes decondense (become long and thin)
    - Nuclear envelope reforms around the two new nuclei.
    - Cytoplasm divides
    - Plasma membrane pinches off
    - Two genetically, identical cells of formed
  • Gametes
    Haploid cells such as an egg or sperm
    - unite during sexual reproduction to produce a diploid zygote
  • Haploid
    An organism or cell having only one complete set of chromosomes.
  • diploid zygote
    fertilized egg
    - contain 46 chromosomes (23 pairs)
  • Meiosis
    Cell division that produces reproductive cells in sexually reproducing organisms

    - involves meiosis I and meiosis II
  • Meiosis I: Interphase
    DNA replication
    > two identical copies of each chromosome (chromatids)
  • Meiosis I: prophase I

    chromatids condense ad arrange themselves into homologous pairs (bivalents)
    > crossing over occurs
    > nuclear envelope disintegrates and spindle fibre form
  • Meiosis I: Metaphase I

    homologous chromosomes line up along the equator and attach to the spindle fibre by their centromeres
  • Meiosis I: Anaphase I

    homologous chromosomes are separated
  • Meiosis: Telophase 1 and cytokinesis
    Chromosomes reach opposite poles of the cell
    > nuclear envelope reforms around the chromosomes
    > cytokinesis results in formation of two daughter cells
  • Meiosis II: Prophase II

    > chromosomes condense
    > nuclear envelope disintegrates
    > spindle fibres form
  • Meiosis II: Metaphase II

    chromosomes attach to the spindle fibre by their centromeres
  • Meiosis II: Anaphase II
    sister chromatids are separated
  • Meiosis II: Telophase II

    chromatids reach opposite poles of the cell
    > nuclear envelope reforms and cytokinesis takes place
    > 4 genetically unique daughter cells
  • 2 ways meiosis increases genetic variation
    - crossing over
    - independent assortment
  • crossing over
    - during prophase I
    - when homologous chromosomes move towards each other and exchange genetic material
    - chromatid from maternal chromosome twist around paternal chromosome and connect through chiasmata
    - piece of chromosomes are exchanges and the chromatids separate
    - forms chromosomes with different combinations of alleles
  • chiasmata
    X-shaped regions where crossing over occurred.
  • independent assortment
    - depends on order in which chromosomes line up along the equator of the cell during metaphase
    - different combinations of chromosomes will end up in each gamete
    - way chromosomes align themselves on the spindle fibre is completely random
    - results in huge number of possibilities of chromosomal combinations in the gametes
  • stem cells
    unspecialised cells that have the ability to become specialised cells ( eg. heart cells or neurones)
  • cell differentiation
    process by which a stem cell is converted from an unspecialised cell to a specialised cell
  • how can stem cell be produced
    have unlimited capacity to divide by mitosis
  • potency
    stem cells undergoing differentiation
  • 4 levels of potency
    - totipotent
    - pluripotent
    - multipotent
    - unipotent
  • totipotent
    ability to divide into any type of cell

    - including extra embryonic cells which make up placenta and umbilical cord
  • pluripotent
    can divide into any type of cell except extra embryonic cells
  • Multipotent
    cells can be divided into a handful of different cell types
  • Unipotent
    cell can only divide into one type of cell
  • example of multipotent adult stem cells
    adult bone marrow

    > divided and differentiated to replace old blood cells
  • where are stem cell present in plants
    in the meristem
    > found in the tip of the shoots and roots

    > they can divide into any kind of cell
  • Uses of stem cells in medicine
    - stem cell transplants
    - developing ways of growing whole organs
  • stem cell transplant
    given to patients with leukaemia
    > type of cancer that destroys stem cells so bone marrow transplant used to replace the lost stem cells