Transcript 1CellCyclePPT

The Cell Cycle
The cell cycle includes the process in which single cells divide to
form TWO identical cells with the SAME number of chromosomes.
I. Why do cells divide?
• Fact: Living things grow, or increase in size. How does this happen?
• A living thing grows because it produces more and more cells.
• If cells simply got BIGGER, they would encounter problems!
 Materials will have trouble entering and leaving the cell
 An “information crisis” would occur! Not enough DNA to code for
all of the proteins the cell would need at a larger size.
II. What is a chromosome?
• Structures in the nucleus that contain the genetic information that is
passed on from one generation of cells to the next.
Chromosome Structure
• During the first stage of cell division, DNA replicates (copies itself)
and condenses around histone proteins to form chromosomes.
• Each chromosome is composed of 2 identical sister chromatids
attached by a centromere
Chromosome:
III. Interphase
Interphase: (“In-between” phase)
• The period between cell divisions; longest phase in the cell cycle
• Period of intense activity
• Divided into 3 phases: G1 (cell growth), S (DNA synthesis), G2
(organelles and materials required for cell division are synthesized)
IV. Mitosis
Prophase: (Piles of DNA into chromosomes)
• Chromatin condenses into distinct chromosomes, nucleolus disappears
• Nuclear envelope begins to break down
• In animals, centrioles separate and take position on opposite sides of nucleus
• Spindle begins to form
Metaphase: (Make a line)
• Chromosomes line up across the center of the cell
• Spindle fibers connect to the centromere of each chromosome
Anaphase: (Apart they go!)
• Centromeres joining the sister chromatids split
• Sister chromatids begin to separate, becoming individual chromosomes
•
Anaphase ends when the movement of chromosomes stops
Telophase: (Two cells forming)
•
Chromosomes begin to uncoil into a tangle of chromatin
•
Spindle breaks apart
•
Nuclear envelopes reform around the chromatin, forming 2 daughter nuclei
•
Mitosis is complete!
Is Cell
Division
over?
V. Cytokinesis
Cytokinesis:
•
To complete the cell cycle, the cytoplasm needs to divide!
• Cytokinesis is the division of the cytoplasm into two individual cells with
identical genetic information.
•
In plants, a cell plate gradually develops into a separating membrane.
•
The Cell Cycle is complete and will begin again!
VI. Animations
Click on the links below to view the processes of
mitosis and cytokinesis!
Mitosis Animation #1
Mitosis Animation #2
Mitosis Animation #3