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Cell Division and Inheritance
The process of growth and development in multicelled organisms is due, for the
most part, to the process of cell division.
This allows the human body to go from a
single fertilized cell to a mature body of approximately 75 trillion cells.
replacement of damaged or aged tissue also takes place mostly through the process of
It is important, therefore, to understand how the process of cell division
(i.e., mitosis) takes place.
When it comes time for the organism to reproduce itself as a whole entity, the
process is somewhat different and is called meiosis.
Here the goal is not to produce an
exact duplicate of the original organism, but to pass just one copy of the genetic material
on into the next generation.
In this lab, we will study the processes of mitosis and meiosis and begin to acquire
some of the language of genetics and heredity.
The cells of the body are of one of two types.
Most of the cells in the body are
The only cells which are not somatic cells are those involved in the
production of sex cells (aka, gametes).
When somatic cells reproduce, it is necessary
for them to produce an exact duplicate of the original cell.
The life of the somatic cell is divided up into several phases.
The vast majority of
the cell's life is spent in
This is the phase in which the cell carries out its
primary functions, e.g., as an epithelial cell in the skin, or a smooth muscle fiber in the
Interphase can be further subdivided.
is where the cell carries
out its specialized function.
, the cell is preparing for cell division;
manufacture of organelles outside the nucleus is increased to provide enough for two
phase is followed by the
, where the chromosomes within the
nucleus are duplicated, preparatory to cell division.
finishes up the
preparations for cell division, being devoted to last-minute protein synthesis and the
completion of centriole
The process of mitosis is also broken down into several phases, beginning with
During prophase, the duplicated chromosomes condense out of the
chromatin, becoming visible under the light microscope.
As the result of chromosome
duplication in the S phase, there are now two copies of each chromosome, held together
by a centromere
; each copy is referred to as a chromatid
, until it is separated from its
duplicate later in the process.
The two pairs of centrioles, produced at the end of the G