BIOL130 Chapter Notes - Chapter 9: Cdk Inhibitor, Spindle Apparatus, Sister Chromatids

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5 Aug 2016
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Unit 9: Cell Cycle, Mitosis, Meiosis
Cell cycle: the time from division to division
 must replicate and accurately distribute DNA to daughter cells
 most cells duplicate macromolecules and organelles and double in size before division
Mitosis: produces two diploid, genetically identical daughter cells
 involves cytokinesis – division of cytoplasm into two daughter cells
Meiosis: produces four haploid, daughter cells with half the hereditary material found in parent
cell
 production of gametes (eggs and sperm)
Human chromosome number: 2n = 46
Cell division – essentrial for growth and development, wound repair, asexual reproduction
(yeast)
Amount of chromosomes does not correlate to complexity of organism
DNA packaging in eukaryotes: DNA double helix wrapped around histone proteins, which tightly
pack together and condense to prepare for mitosis/meiosis to form chromosomes
before mitosis, chromosomes are single stranded and each has a homologous pair (one from
mother and one from father)
 after replication each chromosome duplicates into two sister chromatids, one chromosome =
two identical sister chromatids
Interphase is where the cell spends most of its time, cell grows, produces proteins and
organelles, copies its DNA
 G1: cell spends most of its time, growth, metabolism; cells do their “job”
 S: synthesis phase, DNA is replicated
 G2: cell completes preparation for mitosis, genetic material begins to condense, aster with
centrosomes present
Two skeletal structures required for mitosis:
microtubules of the mitotic spindle (lots of tubulin made in G2 phase, if tubulin polymerization
was inhibited, cell could not begin mitosis)
actin and myosin filaments forms contractile ring
Stages of mitosis
Prophase: major condensation of genetic material, early mitotic spindle
Prometaphase: fully condensed, chromosomes begin to line up along equator, nuclear
envelope and nucleolus disappears
- kinetochore: protein complex on centromere, acts as a docking site for microtubules
Metaphase: line up along metaphase plate, all spindles attached to kinetochore
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