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Cell Cycle & Mitosis Notes
Essential
What is the relationship of the process of mitosis to the growth of organisms and to
Question:
repair of damaged cellular materials? Mitosis is a form of cell division that results in
two daughter cells that are genetically identical to each other and to the original cell.
Mitosis plays an important part in the life cycle of most living things, though to varying
extents. In unicellular organisms such as bacteria, mitosis is a type of asexual
reproduction, making identical copies of a single cell. In multicellular organisms,
mitosis produces more cells for growth and repair. The importance of mitosis for the
individual is influenced by whether it is single-celled or multicellular organism.
Activating
Strategy:
Quick write: I think the statement means that in Biology when a cell is
reproducing, or multiplying in number, it is also dividing by splitting itself into
different parts.
What are the 3 limits for cell size?
1. Diffusion – is fast and efficient over short distances but slow and inefficient over
long distances
2. DNA limits cell size – there is a limit to how quickly DNA can be made into
proteins
3. Surface area to volume ratio – as a cell’s size increases, its volume increases much
faster than its surface area
What are the reasons for cell division?
a. maintain an optimum cell size
b. growth in multicellular organisms
c. asexual reproduction of single-celled organisms
d. to replace dead cells
Chromatin vs. Chromosomes
Chromatin is long strands of DNA wrapped around proteins
Chromosome coiled strands of DNA that look like X’s; becomes like this just before
cell division.
Cell Cycle
During which phases does a cell spend most of its time? Interphase
During S phase the DNA is copied.
Mitosis is the process in which a cells nucleus is divided into 2 new nuclei. Each new
nuclei have the same kind and number of chromosomes as the parent. This is also
called asexual reproduction.
The cell cycle follows the following format.
1. Interphase – preparation phase. Three stages: G1, S, G2 and DNA replication.
Typically in chromatin stage.
2. Mitosis (which is broken into four phases)
a. Prophase – first stage of mitosis. Nuclear envelope begins to disappear; chromatin
coils up and becomes X-shaped chromosomes.
b. Metaphase – chromosomes line up in the middle of the cell. Spindle fibers attach
the centromere on the chromosome. Spindle fibers are produced by centrioles.
c. Anaphase – spindle fibers begin to pull the chromosomes apart. Chromatids now
move toward opposite ends.
d. Telophase – Chromatid reach the poles. Nuclear envelope begins to appear around
the chromatid. In plant cells a cell plate appears down the middle to divide the cell. In
animal cells a cleavage furrow appears to separate the cell.
Mitosis pictures: identify which is each phase:
Metaphase
Telophase
Prophase
Anaphase
3. Cytokinesis- the production of 2 new identical daughter cells from the splitting of the
cell’s cytoplasm.
Mitosis
Result is 2 identical daughter cells.
It is how unicellular organisms reproduce.
In multicellular organisms, cell growth and division results in a group of cells that work
together.
Cell → Tissue → Organ → Organ System → Organism
Cancer
Enzymes control each phase of the cell cycle. Enzymes are proteins.
Cancer is the result of uncontrolled cell growth.
Extra mass of cells is called tumors.
Causes of cancer are both genetic and environmental (UV rays, smoke, and viral
infections).