-unicellular organisms: one cell divides, reproduce entire organism.
multicellular organisms: development from a fertilized cell, growth, repair.
the life of a cell from formation to its own division.
most cell division results in...
daughter cells with identical genetic information, DNA.
produces nonidentical daughter cells.
all the DNA in a cell: can consist of single or many DNA molecules.
Packaged DNA molecules in a cell.
-each species has a set number of chromosomes (humans 46, hedgehogs 90).
(nonreproductive cells) have two sets of chromosomes.
have half of chromosomes (humans 23)
before cell division:
DNA replicated, chromosomes condense.
site where chromatids most closely attached.
what is chromatin made up of?
DNA and proteins
division of genetic material in nucleus.
division of cytoplasm.
mitotic (M) phase
mitosis and cytokinesis.
90% of the cycle; cell growth and copying of chromosomes in preparation for cell division.
eukaryotic cell division
overall cell cycle
-g1 phase (first gap; cell growth)
-s phase (synthesis; cell growth and chromosome duplication)
-g2 phase (second gap; cell growth)
what is being synthesized in the S phase of interphase?
at what stage is the cell just prior to mitosis?
G2 of interphase
-nuclear envelope surrounds nucleus.
-centrosome has duplicated.
-chromatin has duplicated (but not yet condensed).
microtubule organizing center. has two centrioles. part of the mitotic spindle.
apparatus of microtubules that controls chromosome movement during mitosis.
-includes centrosomes, spindle microtubules, and asters.
radial array of short microtubules extending from each centrosome.
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.
what material is the metaphase plate made of?
nothing it is imaginary.
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).