The Cell Cycle Section 2.4 BC Science Probe 9 Pages 49-52
The Cell Cycle • The cell cycle is the sequence of events in the cell from one cell division to another.
The Cell Cycle • The cell spends most of its time growing and working. This is called interphase.
The Cell Cycle • Interphase takes up 90% of the cell cycle.
The Cell Cycle • Interphase is when the cell makes copies of each organelle in the cytoplasm. • Once the cell is large enough, it will also make copies of its chromosomes. • Each chromosome and its copy are known as sister chromatids. • They carry identical instructions.
The Cell Cycle • Interphase and cell division together make up the cell cycle.
Cell Division • In cell division, one cell (the parent cell) divides into two genetically identical cells (the daughter cells).
Cell Division • There are two parts to cell division: • Mitosis • Mitosis divides the nuclear material
Cell Division • There are two parts to cell division: • Cytokinesis • Cytokinesis is the process that divides the cytoplasm and the rest of the organelles in half.
Cell Division • Each daughter cell gets about half of the cytoplasm and organelles and will be about half the size of the parent cell.
The Stages of Mitosis • There are 4 stages of mitosis; • Prophase • Metaphase • Anaphase • Telophase
The Stages of Mitosis #1 – Prophase • The DNA molecules shorten andcondense by coiling, to form chromosomes. The nuclear membrane and nucleolus are no longer visible. • The spindleapparatus (and in animal cells, the centrioles) has migrated to opposite poles of the cell..
The Stages of Mitosis #2 – Metaphase • The spindle fibres attach themselves to the sister chromatids and align the chromosomes halfway between the poles of the cell (down the middle).
The Stages of Mitosis #3 - Anaphase • The spindle fibres shorten and the centromere splits, separated sister chromatids are pulled along behind the centromeres.
The Stages of Mitosis #4 – Telophase • The chromosomes reach the poles of their respective spindles. Nuclear envelope reforms before the chromosomes uncoil. The spindle fibres disintegrate.
Cytokinesis • This is the last stage of cell division. It is the process of splitting the daughter cells apart. A furrow forms and the cell is pinched in two. Each daughter cell contains the same number of chromosomes.
Cytokinesis • It’s a little different in plants: • There’s no furrow/indentation. • Vesicles form between the nuclei, fuse together to form a cell plate which grows out to the membrane and grows a new cell wall.