• The Cell Cycle—

An Overview

• Prokaryotic CellDivision

Cell Cycle & Reproduction – Part ISpring 2013 - Althoff Reference: Mader & Windelspecht Ch. 9)

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CELL CYCLE

_________

G1 G0

G2 S

Cell Cycle facts

• New cell produced from pre-existing cell (____________________________!)

• Start with 1 cell, end up with 2• If no mutations/duplication of DNA errors, then

both cells are identical• Associated with _______________ cells only• Most of the time, any individual cell is in

_________________. That is reflected in the previous graphic…90% estimated of the cell cycle

Control of the Cell Cycle: Signals• Both __________ and __________ signals

“control” the cell cycle.

• Those that are internal: must have come from molecule(s) produced by “this” cell

• Those that are external: must have come from molecule(s) produced by __________ _____…or a cell somewhere else _______ _____________

• Signals control the 1) _________ of events (stages & phases) AND 2) that _________ ____________________________

Outside Signals

• Must pass through the _________________

• ______________________ is the name given to outside signals

• These would have effect (i.e, result in “action” by the cell) during interphase (stages G1 S G2)…the period of ____________ and DNA replication

One “________________” inside Enzyme

• __________ is defined as programmed cell death • This means that the “death” of the cell will occur

through a _______ series of events that eventually breaks up the cell (see Mader p155, Fig. 9.2)

• This is facilitated by the enzymes known as CASPASES. These enzymes are apparently always present in the cell. During early cell life they are held in check by inhibitors within the cell. When it “is time”, signals (i.e., proteins) can come internally or externally to _____________ of the cell

ApoptosisApoptosis

Fragments are ___________ (i.e., engulfed) by white bloodcells and neighboring cells.

The Cell Cycle: CHECKPOINTS

• During the cell cycle, there are checkpoints that, based on _____________ and/or ___________ IN CYCLINES, determine if the cell cycle proceeds to the next stage

• At these checkpoints two basic things can happen:

a) the “work” of that stage can be caught up and/or repaired

b) the cell can be signaled to stop andapoptosis be allowed to take place

Fig 9.1, p151 from Mader…The checkpoint graphic side only

G1

G2

CHECKPOINTS on the cell cycle…________________________

M2

Apoptosis: “good” examples• Cell “death” isn’t as bad as it might seem…at least when

we are talking about complex organisms

• _______: initially, as tadpole, have a tail. At some point all cells associated with the tail succumb to apoptosis.

• ________________—during embryotic stages, have webs connecting them. Those cells eventually succumb to apoptosis

• _____: born blind (i.e., eye lids closed). At 8-12 days cells along a line dividing the upper from lower eye lid undergo apoptosis.

PROKARYOTIC CELL DIVISION

• Remember, these are ALL unicellular (single-cell) organisms

• Cell division results in _________________• The process is known as

______________________• Offspring are genetically identical to parent

as long as __________________• A single chromosome is duplicated, with a

copy going to each daughter cell

PROKARYOTIC CELL DIVISION

• Remember, these 2 domains (bacteria and archaea) lack 1) membranous organelles and 2) a nucleus

• The chromosomes for prokaryotes contain fewer proteins and organized ___________ than eukaryotic chromosomes

• For bacteria, this chromosome containing area is known as the ___________. When stretched out, it looks more loop-shape in appearance rather than strand-shaped.

BINARY FISSION

• This is term associated with prokaryotic asexual reproduction. With 5 basic steps:

The cell ____________DNA __________ (to 2 chromosomes)The chromosomes _______ to the plasma

membrane while the cell elongates and as…

new plasma membrane and cell wall developAnd the cell wall—at a point—___________Cytoplasm is divided, then 1 becomes __!

BINARY FISSION

(Mader p166, Fig. 9.9)

12

3

4

5

PROKARYOTES: Binary Fission

• Can happen _____________ fast…when compared to Eukaryotic cell division

• Example: Escherichia coli (E. coli).In the human intestine, under favorableconditions can divide in about ____ min.

In ___ hours, a single cell can result in___________ cells.

• Put this rate of _______________ into perspective from ingestion to “problems” timeframe

Functions of Cell Division

Type of Organism Cell Division Function

Prokaryotes Bacteria & archaea

Eukaryotes Protists & some fungi (yeast)

Eukaryotes Other fungi, plants, animals

Binary AsexualFission Reproduction

Mitosis & AsexualCytokinesis Reproduction

Mitosis & Development,Cytokinesis Growth & Repair

Make sure you know these terms AFTER these lecture…

• Mitosis• Cell Cycle Stages =

G1SG2M• InterphaseProphaseMetaphaseAnaphaseTelophase• Cytokinesis• Apoptosis

• Cyclins• Cell Plate – plants only• Cleavage furrow –

animals only• Neoplasm• Malignant• Benign

• Binary Fission• Asexual Reproduction