Meiosis
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Meiosis
is the process in which gametes, or eggs and sperm, are created. This process varies from mitosis in a few
ways, most notably the fact that exact replicates of the original cell are
not created. From meiosis comes four
new cells, each with a haploid or monoploid number of chromosomes. The processes of spermatogenesis and
oogenesis are what create the sperm and eggs. |
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In
the testes, there is a primary sex cell with a diploid number of
chromosomes. When the primary cell
has matured, the homologous chromosomes come together in pairs in a process
called synapsis. It is during
synapsis that the exchange of genetic material between homologous chromosomes
known as crossing over occurs. The
chromosomes then replicate and divide into two monoploid cells through
reduction-division. These cells then
divide mitotically to give two pairs of cells that reorganize most of their
cytoplasm into tails, thus creating sperm. |
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In
the ovaries, the same process occurs until the reduction-division phase. When the cell divides, more cytoplasm goes
into one cell than the other. This occurs
again when those two cells divide mitotically. This produces one monoploid mature egg cell, and three useless
smaller cells known as polar bodies.
The polar bodies eventually disintegrate. |
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When
two monoploid gametes come together, they form one diploid cell with half a
set of chromosomes from each parent.
It is from this union that a new organism develops. |
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