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Watch this video on the cell cycle and mitosis.
Watch this video on the cell cycle and mitosis.
Why do cells divide using mitosis???
Why do cells divide using mitosis???
Asexual Reproduction: ONLY for unicellular organisms (like bacteria) that reproduce without a partner.
Growth: More cells = a larger organism
Repair: To replace old or damaged cells
The Cell's life cycle is 3 stages:
The Cell's life cycle is 3 stages:
Stage 1: INTERPHASE - The cell is growing, DNA is copied, and the cell is doing it's job. Longest stage (about 90% of the cells life cycle is spent in interphase)
Stage 2: MITOSIS - DNA copies are separated and the nucleus divides. Short stage (about 10% of the cell's life cycle is spent in mitosis)
Stage 3: CYTOKINESIS - The cell membrane closes around each new nucleus and forms 2 identical cells.
New cells replace old cells, allow growth, Etc...
The Phases of mitosis:
The Phases of mitosis:
Prophase:
Prophase:
Prior to prophase the DNA is uncoiled and loose in the nucleus (chromatin). Think of it like a bowl of spaghetti... That makes it difficult to sort into two groups so during prophase the DNA condenses by wrapping tightly around proteins and then supercoiling into tightly packed chromosomes that is attached to it's duplicate strand.
The nucleus breaks up and disappears so that the DNA can move around and separate. Often denoted by a dotted line.
Spindle fibers (microtubules) form from the centrioles at each end of the cell (aids in separating the chromosomes).
Metaphase:
Metaphase:
In metaphase the spindle fibers attach to the centromere at the center of each chromosome and help line up the chromosomes in the center of the cell. Metaphase = middle
Anaphase:
Anaphase:
The DNA gets duplicated during interphase so that both new cells can have a complete copy of instructions. The separation of these copies happens in anaphase. Anaphase = Away
Chromosomes are pulled apart and sorted so that each end of the cell gets a complete copy of each chromosome (made of DNA).
Telophase:
Telophase:
The nucleus reappears at both ends of the cell. This is also denoted by a dotted line (as we saw in prophase when it disappeared) but you know it is telophase if there are two of them.
Evidence of Cytokinesis is apparent. Cytokinesis = separation of cytoplasm
Cytokinesis:
Cytokinesis:
Separation of the cytoplasm.
Plant cells will form a cell plate in the middle that will grow to form the cell wall.
Animal cells will form a furrow that will pinch off until the cell becomes TWO IDENTICAL CELLS.
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