Term
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Definition
• occurs only in reproductive cells
• results in cells that have half the chromosomes of the parent cell
• one diploid parent cell makes four haploid gametes
• occurs only prior to formation of gametes
• basis of sexual reproduction
• physical basis for eukaryotic genetics |
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Term
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Definition
• happens in somatic cells
• results in daughter cells that are genetically identical to parent cell
• usually accompanied by cytokinesis
• responsible for growth, wound repair and reproduction
• purpose: distribute parent cell's genetic material to daughter cels during cell division
• prior to mitosis, each chromosome is copied
• at end of mitosis, one chromosome distributed to each daughter cell |
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Term
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Definition
• single, long DNA double helix that is wrapped around in proteins in a highly organized manner
• can only be stained and observed during M phase |
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Term
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Definition
• each of the DNA copies in a replicated chromosome
• joined along entire length and at centromere
• one continuous DNA molecule wrapped around proteins |
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Term
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Definition
| where each set of chromatids is joined |
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Definition
| chromatids from same chromosome |
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Term
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Definition
| protein associated with DNA in the chromatin of eukaryotic cells |
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Term
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Definition
structure that produces mechanical forces that pull chromosomes into daughter cells during mitosis
• made of microtubules, which are made of α-tubulin and β-tubulin dimers
• length of microtubule determined by how many dimers it contains
• microtubules are asymmetric and grow at plus end
• spindle fibers grow from centrosome until plus end attaches to kinetochore |
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Term
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Definition
o microtubule organizing center
• contains pair of centrioles
• kinetochore: where spindle fibers and chromatids attach
• located at centromere
• each chromosome has two kinetochores where spindle fibers attach, one on each side |
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Term
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Definition
thought to have a base that attaches to centromere region of chromosome and crown of fibrous proteins projecting outward
• contains dyneins and other motor proteins
• attached to crown
• capable of walking down microtubules from plus to minus
• proteins in kinetochore catalyze loss of tubulin subunits at plus end while dyneins and other motor proteins walk toward minus end |
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Term
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Definition
| depiction of complete set of chromosomes |
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Term
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Definition
| measure of total DNA a cell has, measured in base pairs of DNA – think about it as chromatids |
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Definition
| some chromosomes coil on a different cycle; short and think instead of long and thin |
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Term
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Definition
o polypeptides or small proteins responsible for stimulating cell division
• also stimulates production of key regulatory protein, E2F
• when cells are in G0, arrival of growth factors stimulates production of cyclins (analogous to MPF)
• triggers expression of genes needed for S phase
• when first produced, binds to a tumor suppressor protein (Rb)
• when E2F bound to Rb, in off position (can’t activate S phase) |
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Term
| if growth factors continue to arrive |
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Definition
• production of cyclins and therefore cyclin-cdk complexes continues
o cyclins are specific to G1 checkpoint
• when activated, being phosphorylation of Rb, which means it can’t bind to E2F anymore
• E2F now free to activate target genes and S phase starts |
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Term
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Definition
| one of key molecules that enforces G1 checkpoint |
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Term
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Definition
o phase of cell cycle in which cell is not dividing, everything other than mitosis (where cells spend most of their time)
o three parts
• S phase: time during which DNA is replicated
• G1: busiest time for cell metabolism and growth
• G2: allows cell to build protein machinery necessary to mitosis
o gap phases exist so cells can replicated organelles and manufacture additional cytoplasm and grow large enough |
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Term
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Definition
o phase of cell cycle in which cell division occurs
o at start, each chromosome consists of two sister chromatids attached to one another at centromere
o divided into stages (IPPMAT) |
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Term
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Definition
step 1 of mitosis
DNA gets packaged and ready for movement
• chromosomes already replicated from interphase
• DNA is complex with proteins (histones) into chromatin
• chromatin condenses (first becomes visible)
• marked by formation of mitotic spindle |
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Term
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Definition
step 2 of mitosis
• nuclear envelope breaks down and nucleolus disappears
• spindle fibers from each centromere attach to one of two sister chromatids at kinetochore
• centrosomes begin moving to opposite poles
• spindle fibers attached to kinetochores begin to move chromosomes to middle of cell |
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Term
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Definition
step 3 of mitosis
• chromosomes line up at metaphase plate
• mitotic spindle is fully formed
• each chromosome is held by kinetochores reaching to opposite poles and exerting same amount of tension (tug of war) |
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Term
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Definition
step 4 of mitosis
• separating duplicated chromosomes
• become full-fledged chromosomes
• spindle fibers attached to kinetochores shorten, pulling sister chromatids apart via motor proteins
• spindle fibers not attached to kinetochores begin to push against each other via motor proteins that connect them, causing poles of cell to be separated even more
• chromatids pull to opposite poles so that each daughter cells gets identical sets of chromosomes
• kinetochore microtubules remain stationary during anaphase
o microtubules shorten at kinetochore because tubulin subunits are lost from plus ends |
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Term
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Definition
step 5 of mitosis
• nuclear envelope re-forms and mitotic spindle disappears
• chromosomes begin to de-condense
• once two independent nuclei have formed, mitosis is complete |
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Term
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Definition
• division of cytoplasm to form two daughter cells
• usually occurs immediately after mitosis |
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Term
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Definition
cleavage furrow forms between two new nuclei
o made from ring of actin and myosin microfibrils that surround inside circumference of cell
o microfilaments contract, causing cell membrane to constrict and pinch cell in two |
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Term
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Definition
• a cell plate forms
o vesicles from Golgi apparatus carrying cell-wall material migrate to middle of cell between two new nuclei
o vesicles build up and fuse, forming new cell membrane and cell wall |
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Term
| length of cell cycle various enormously, mostly due to___________ |
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Definition
variation in length of G1
in rapidly dividing cells, practically no G1 |
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Term
| non-diving cells stay in ________ |
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Definition
o a G1-like phase (G0) indefinitely
• sometimes referred to as post-mitotic
• nerve and muscle cells |
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Term
| cyclin/cdks serve as ________ |
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Definition
| switches that push cell from one cell-cycle phase to next |
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