RAPID
METHODS
FOR
SEAFOOD
INDUSTRY
97
The colored spots correspond
to
the colonies
of
the target microorganism
on
the
master
plate.
Gene
Probes,
DNA/RNA
Hybridization
A gene
probe
is a
short length of
nucleic acid
(DNA
or
RNA)
which
consists
of
either an entire
gene
or
a fragment
of
a
gene.
Both
DNA and
RNA
probes are
used
to detect
complementary
DNA
or
RNA
of
target microorgan-
isms in foods. Gene probes
will
pair with
complementary
sequences
of
single-
stranded
DNA
extracted from bacterial cultures.
Gene
probes have regions
of
homology
with specific
sequences in
the
DNA of
the targeted organism
and
will
pair
with
these
complementary sequences
to form
a
hybrid double helix. The
gene probe carries
a label which
facilitates the detection
of
the hybridization
product.
When targeted
DNA
is
absent,
no
hybridization occurs.
DNA
target
sequences most
often are
double-stranded
and must
be denatured before the
hybridization process.
RNA
target sequences
are
usually
single-stranded
and
do
not
need
to
be
denatured. Additionally, probes
can
be targeted
against
either
DNA
or
RNA
of
bacteria.
A
number
of
commercially
available gene probes are
RNA probes,
enzymatically
or
radioactively labeled and
are
targeted to bacterial
ribosomal RNA
(rRNA).
Ribosomal RNA is present
in multiple copies
(about
1,OOO)
in
the bacterial cell
whereas
DNA
is present
in
a
single copy.
By
using
rRNA
as
a
target, the sensitivity
of
the
assays
increases.
RAPID METHODS FOR SEAFOOD INDUSTRY 97 The colored spots correspond to the colonies of the target microorganism on the master plate. Gene Probes, DNA/RNA Hybridization A gene probe is a short length of nucleic acid (DNA or RNA) which consists of either an entire gene or a fragment of a gene. Both DNA and RNA probes are used to detect complementary DNA or RNA of target microorgan- isms in foods. Gene probes will pair with complementary sequences of single- stranded DNA extracted from bacterial cultures. Gene probes have regions of homology with specific sequences in the DNA of the targeted organism and will pair with these complementary sequences to form a hybrid double helix. The gene probe carries a label which facilitates the detection of the hybridization product. When targeted DNA is absent, no hybridization occurs. DNA target sequences most often are double-stranded and must be denatured before the hybridization process. RNA target sequences are usually single-stranded and do not need to be denatured. Additionally, probes can be targeted against either DNA or RNA of bacteria. A number of commercially available gene probes are RNA probes, enzymatically or radioactively labeled and are targeted to bacterial ribosomal RNA (rRNA). Ribosomal RNA is present in multiple copies (about 1,OOO) in the bacterial cell whereas DNA is present in a single copy. By using rRNA as a target, the sensitivity of the assays increases.
การแปล กรุณารอสักครู่..