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AP Bio Midterm - Chapter 12


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A cell's endowment of DNA - genetic information - passed to each daughter cell
46 chromosomes in human
Somatic cells
23 chromosomes in humans - same genes; homologus
DNA molecules packaged
DNA-protein comles; after a cell duplicates its DNA in preparation for division, it condenses - densely coiled
Each duplicated chromosome has two of these
Sister chromatids
Chromosome's narrow "waist" in condensed form
The division of the nucleus usually followed immediately by cytokenesis - copies of sister chromatids pulled apart
The division of the cytoplasm
Yields daughter cells that have half as many chromosomes as the parent cell; occurs only in gonads
Includes both mitosis and cytokenesis; shortest part of the cell cycle
Miotic (M) phase
90% of the cycle; the cell grows and copies its chromosomes in preparation for cell division
Amitotic stop at G1 phase; will go and divide
Go phase
First gap; makes proteins needed and grows
G1 phase
Chromosomes are duplicated here only
S phase
Second gap; grows more
G2 phase
Forms in the cytoplasm during prophase; consists of fibers of microtubules and associated proteins
Mitotic spindle
The assembly of spindle microtubules start here; nonmembrane organelle that functions throughout the cell cycle to organize the cell's microtubules
Structure of proteins and specific sectoins of chromosomal DNA at the centromere
Triggers breakdown of cyclin and inactivates proteins holding sister chromatids together
An imaginary plane during metaphase in which centromeres of all duplicated chromosomes are located midway between the two poles
Metaphase plate
In animal cells, cytokenesis occurs by this
Cleavage furrow
"Division of half"; prokaryotes reproduce by this type of cell division; most bacterial cells carried on a single bacterial chromosome that consists of a circular DNA molecule and associated proteins
Binary Fission
Cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle
Cell Cycle Control System
A critical control point where stop and go ahead signals can regulate the cycle; 3 found in G1, G2, and M phases
Activate or inactivate by phosphorylating proteins (they are enzymes) - concentration constant - usually in inactive form
Protein kinases
Give go-ahead signals at the G1 and G2 checkpoints
Particular kinases
Kinase must attatch to this to be active; protein that cyclically fluctuating concentration in the cell; these kinases are called cyclin-dependent kinases (CdKs)
Activity correspond to the peaks of cyclin concentration; "maturation-promoting factor"; triggers the cell passage past the G2 checkpoint to the M phase
Protein released by certain body cell
Growth factor
Crowded cells stop dividing
Density-dependent inhibition
Animal cells must be attracted to a substratum; signaled to the cell cycle control system via pathways involving plasma membrane proteins and elements of the cytoskeleton linked to them - ECM; checks growth of cells
Anchorage dependence
Tumor returns to original site; don't cause serious problems and can be completely removed
Benign tumor
Becomes invasive enough to impair the functoin of normal organs
Malignant tumor

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