Mitosis and Meiosis
Mitosis and Meiosis describes the
process by which the body prepares cells to participate in either asexual or sexual reproduction to make an entire organism.
Examples of Mitosis and Meiosis
Mitosis is the
reproduction of skin, heart, stomach, cheek, hair etc. cells. These
cells are "Autosomal" cells. This is also a form of "Asexual"
reproduction, where one organism or cell reproduces itself. Some
organisms that reproduce asexually are hydra, bacteria, and single
celled organisms.
"A" greek meaning "without."
- "Sex" Greek meaning "to cross."
Meiosis is the
production of sperm and egg cells. These cells are "Gamete" or "Sex"
cells. Each cell has to go through the division process twice in order
for the cell to end up with half the number of chromosomes. The cells
pass on genetic information to the offspring. This is a form of
"Sexual" reproduction, where one organism or cells reproduces by
crossing with another organism or cell. Types of organisms that
reproduce sexually are; plants, animals, and insects.
- For either of these processes of reproduction we must
first understand the basic Chromosome structure that the body uses in
either Mitosis or Meiosis.
Mitosis: --
One cell becomes two cells-- The new
"daughter" cell has exactly the same number of chromosomes and
information as the "parent" cell. 1 cell divides and becomes 2 cells.
Meiosis: --
One cell becomes 4 cells--There are 4 new "daughter" cells. Each new gamete cell contains only
one-half
of the number of chromosomes of the parent cell. Each sex cell goes
through the division process twice in order to have the correct number
of cells, and the correct chromosomal information. (Look carefully at
the diagram below to understand how each chromatid becomes part of a
new sperm or egg cell. Go back to the first diagram if necessary to
study what a chromosome pair, chromatid, and allele is.)
In
female mammals (humans too) 3 of the gametes do not mature with a full
yoke sack. Only 1 of the 4 can become a mature egg. All mature eggs are
formed to a certain stage in the first division.
In male mammals (humans too) all 4 gametes mature into sperm cells. The
male is continually forming these after birth.
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