Flashcards in 3. Cellular reproduction: the cell cycle Deck (52)
in single celled organisms, cellular reproductions ensures ___________ of species.
-1 cell (zygote) divides to become highly organized complex of many of cells
-cell division continues through life
-adult humans have millions dividing at any moment
-replaces old, damaged cells
the time from one division to the next division
cell cycle is divided into 2 visible phases:
interphase and Mitotic phase (M phase)
G1, S, G2
-cell growth and metabolism
-length of interphase can vary depending on cell type
-includes mitosis (nuclear division) and cytokinesis (cell division)
-occurs after interphase
MITOSIS (prophase, prometaphase, metaphase, anaphase, telephase)
cell grows and carries out normal metabolism; organelles duplicate
DNA replication and chromosome duplication
cell grows and prepares for mitosis
Cells can be grouped into 3 broad categories with respect to cell cycle
1. cells that do no cycle, but enter a permanent arrest stage (G0)
(ex. neurons, muscles cells, RBCs- once differentiated, they remain in that state until they die)
2. Cells that normally do not divide, but can be induced
(eg. liver cells, lymphocytes- liver cells reproduce with infection or too much alcohol. the damaged liver cells need to be replaced)
3. Cells that divide regularly
(eg. epithelial cells that line body cavities and surfaces)
How is cell cycle controlled?
Cytoplasmic factors control cell division
Who did and experiment where they fused mitotic and interphase cells?
Rao and Johnson (1970)
What did Rao and Johnson found?
if interphase cells were in G1, they observed "premature chromosomes" (slightly condensed)
I.e the non-mitotic cell tried to enter M phase
What did Rao and Johnson conclude?
a "factor" present in the mitotic cell directs cells to undergo mitosis
Entry into mitosis requires a protein complex called _____________.
Maturation promoting factor or MPF
(Rao and Johnson's factor)
MPF is a complex of two proteins:
1. Cyclin b
2. Cdk1 (cyclin dependent kinase)
-regulates Cdk1 activity
-levels rise and fall throughout cell cycle
(cyclin dependent kinase )
-a kinase is a protein that adds a phosphate to other proteins; the activity of the target protein is modified.
In what phase does cyclin b increase its concentration?
decreases in M phase
In what phase does MPF increase its concentration?
end of G2 and beginning of M.
MPF phosphorylates and activates _______ of _______.
In the ______ phase, cyclin creases enough to bind to _______.
Some MPF functions (3)
1. activates lamin proteins- causes nuclear envelope to break up
2. alters DNA-bound proteins (histones)- causes DNA to condense
3. activates proteins of mitotic spindle
introduce a phosphate group into a molecule or compound
third tenet of cell theory
new cells originate only from other living cells
not a mutant
M forms two daughter cells
- sign indicates a _______
Wee1 and Wee1-
Wee1 protein is an inhibitor of MPF (prevents mitosis)
Wee1- mutant lacks inhibitor- results in early division ( the cell divides prematurely, prematurely creat daughter cells, forming small cells )
Cdc25 and Cdc25-
Cdc25 protein activates MPF
Cdc25- mutant lacks activator, division fails to occur; the cell does not divide but continues to grow resulting in an overly large cell