-unicellular organisms: one cell divides, reproduce entire organism.
multicellular organisms: development from a fertilized cell, growth, repair.
Packaged DNA molecules in a cell.
-each species has a set number of chromosomes (humans 46, hedgehogs 90).
90% of the cycle; cell growth and copying of chromosomes in preparation for cell division.
-g1 phase (first gap; cell growth)
-s phase (synthesis; cell growth and chromosome duplication)
-g2 phase (second gap; cell growth)
G2 of interphase
-nuclear envelope surrounds nucleus.
-centrosome has duplicated.
-chromatin has duplicated (but not yet condensed).
apparatus of microtubules that controls chromosome movement during mitosis.
-includes centrosomes, spindle microtubules, and asters.
chromatin condenses into sister chromatids; assembly of spindle microtubules begins, centrosomes migrate to opposite poles as spindle microtubules grow out from them.
a structure of proteins associated with specific sections of DNA at each centrosome.
-a chromosome has 2 kinetochores facing in opposite directions.
nuclear envelope fragments; chromatids get kinetochores; some spindle microtubules attach to kinetochores and jerk back and forth; nonkinetochore microtubule attachments also form.
-centrosomes at opposite poles.
-chromosomes line up at the metaphase plate, the midway point between the spindle's two poles.
-kinetochores arranged so for each chromosome, one kinetochore attached towards each pole.
sister chromatids separate (cohesion proteins cleaved); each chromosome moves along kinetochore microtubules toward opposite poles.
-microtubules shorten by depolymerizing at kinetochore ends.
-nonkinetochore microtubules from opposite poles overlap and push against each other, elongating cell.
genetically identical daughter nuclei form at opposite ends of the cell; nuclear envelopes form; chromosomes become less dense; spindle dissolves.
separation of cytoplasm occurs differently in animal and plant cells.
-each new cell gets its share of cytosol, organelles, etc.
cytokinesis (animal cell)
cytokinesis occurs by cleavage; a process of forming a cleavage furrow, or contractile ring of actin microfilaments associated with myosin, that pinches the parent cell in two.
cytokinesis (plant cell)
cytokinesis occurs by forming a cell plate; coalesced vesicles containing cell wall materials, that eventually grows to fuse with membrane around cell, dividing cell into two.
centrosome, centriole, centromere
centrosome: microtubule organizing center that is part of the mitotic spindle.
-centriole: this is one of the two bodies marking the location of the centrosome.
-centromere: this is the tight point of connection between two sister chromatids (region of specific DNA sequences where chromatids attach most closely).