Nucleolus
The
nucleolus
is
an
approximately
spherical
region
within
the
nucleus
of
eukaryotic
cells.
It
consists
of
nucleolar
organizers
and
ribosomal
subunits.
Nucleolar
organizers
are
special
regions
on
some
chromosomes
that
contain
multiple
copies
of
the
genes
encoding
for
rRNA
the
ribosomes
which
are
involved
in
protein
biosynthesis.
Following
synthesis,
the
rRNA
is
attached
to
the
ribosomal
subunits
in
the
nucleus
before
transport
through
the
nuclear
pores
into
the
cytosol.