The Cell Cycle: Chp 12 Flashcards
cell cycle
the life of a cell from the time it is first formed from a dividing parent cell until its own division into two cells
genome
the cells genetic information
somatic cells
all body cells except gametes (they have 46 chromosomes)
mitosis
the process by which somatic cells divide, forming daughter cells that contain the same chromosome number as the parent cell
gametes
sperm and egg cells (haploid). they go through meiosis
sister chromatids
there are 2 and they are each of the duplicated chromosomes when they are attached
centromere
where the two sister chromatids attach
mitosis
the division of the cell’s nucleus (1 cell turns to 2)
cytokinesis
the division of the cells cytoplasm
interphase
90% of the cell cycle that consists of G1, S, and G2 phases
G1 phase
first portion of interphase. the cell grows while carrying out cell functions unique to its cell type
S phase
second portion of interphase. the cell continues to carry out its unique functions but does one other important process-it duplicates its chromosomes meaning it makes a copy of DNA that makses up the cells chromosomes
G2 phase
the last portion of interphase. the gap after the chromosomes have been duplicated and just before mitosis
prophase
1: the chromatin becomes more tightly coiled into discrete chromosomes
2: the nucleoli disappears
3: the mitotic spindle begins to form in the cytoplasm
premetaphase
1: the nuclear envelope begins to fragment, allowing the microtubules to attach ot the chromosomes
2: the two chromatids of each chromosome are held together by protein kinetochores in the centromere region
3: the microtubules will attach to the kinetochores
metaphase
1: the microtubules move the chromosomes to the metaphase plate at the equator of the cell. the microtubule complex is referred to as the spindle.
2: the centrioles have migrated to opposite poles in the cell, riding along on the developing spindle
anaphase
1: sister chromatids begin to separate, pulled apart by motor molecules interacting with kinetochore microtubules
2: the cell elongates, as the nonkinetochore microtubules ratchet apart, again with the help of motor molecules
3: by the end of anaphase, the opposite ends of the cell both contain complete and equal sets of chromosomes
telophase
1: the nuclear envelopes re-form around the sets of chromosomes located at opposite ends of the cell
2: the chromatin fiber of the chromosomes becomes less condensed
3: cytokinsesis begins, which is where the cytoplasm of the cell is divided. In animal cells, a cleavage furrow forms and divides. in a plant cell, a cell plate forms that divides the cytoplasm
4: prokaryotes replicate their genome by binary fission rather than mitosis
cell cycle control system
this controls the steps of the cycle. It moves the cell through stages by a series of checkpoints where signals tell the cell to either continue dividing or stop.
The major cell checkpoints
G1 phase checkpoint, G2 phase checkpoint, and M phase checkpoint
G1 phase checkpoint
seems the most important. if the cell gets the go-ahead signal, it usually completes the whole cell cycle and divides. If it does not receive the signal, it enters a nondividing phase called the G0 phase
kinases
the protein enzymes that control the cell cycle. they exist in the cells at all times but are active only when they are connected to cyclin protein; thus, they are called cyclin-dependent kinases
denisty dependent inhibition
the phenomenon in which crowded cells stop dividing
anchorage dependency
normal cells must be attached to a substrate tum, like the extracellular matrix of a tissue, to divide
