solid ball of cells; totipotent; no differentiation; can become entire organism
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Blastula (embryonic stem cell)
hollow ball of cells; pluripotent; slightly differentiated; can become over 200 cell types
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Adult stem cell
multipotent; partly differentiated; can become a few cell types
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Tissue cell
no level of potential; fully differentiated; no further changes in cell
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interphase
G1, S, G2
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Four phases of mitosis
prophase, metaphase, anaphase, telophase
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prophase
Chromatin condenses into chromosomes; nuclear envelope breaks down; centrioles separate (animal cells); spindle begins to form
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metaphase
Chromosomes line up at the center of the cell
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anaphase
spindle fibers shorten and pull the sister chromatids apart to opposite poles of the cell
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telophase
chromosomes uncoil to form chromatin; spindle breaks down; new nuclear membranes form
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G1
After cytokinesis; cell grows rapidly while metabolic processes are performed; proteins for DNA replication are produced + copies of some organelles to prepare for cell division
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S
DNA of cell is replicated
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G2
final preparations for cell division are made; cell grows rapidly (ex. additional proteins + organelles are produced)
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M
mitosis + cytokinesis; genetic material is divided into 2 daughter cells + cytoplasm divides; occurs in four stages (prophase, metaphase, anaphase, telophase)
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G0
"cell arrest"; resting phase where cells stop dividing/preparing for division; can be temp or perm
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Healthy cells need to divide...
when an organism needs to grow; when a cell gets old + dies; when a cell gets damaged
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histone proteins
proteins that form a sphere + DNA wraps around it
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nucleosome
DNA segment coiled around histone proteins sphere
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chromatin
loosely to moderately coiled nucleosomes; accessible to DNA + RNA polymerases
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chromosome
tightly coiled nucleosomes; not accessible to DNA + RNA polymerases
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sister chromatids
two identical arms of replicated chromosomes; found on a single chromosome
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increasing order of compactness
DNA double helix \>> nucleosome \>> chromatin \>> chromosome
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homoglous chromosomes
chromosomes that have same genes but possibly different versions
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after what pt in cell cycle are sister chromatids present:
after DNA replication
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G1 checkpoint
Decides if cell division is necessary or not; if DNA is undamaged + enough available resources, then checkpoint is passed
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G2/S checkpoint
determines if the DNA has been replicated properly
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M checkpoint
checks if the 2 sister chromatids in a duplicated chromosome are both attached to spindle fibers + are properly aligned; if so, they become 2 chromosomes + move to opposite ends of the dividing cell
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