<< Chapter < Page Chapter >> Page >

To screen a genomic library for a particular gene or sequence of interest, researchers must know something about that gene. If researchers have a portion of the sequence of DNA for the gene of interest, they can design a DNA probe , a single-stranded DNA fragment that is complementary to part of the gene of interest and different from other DNA sequences in the sample. The DNA probe may be synthesized chemically by commercial laboratories, or it may be created by cloning, isolating, and denaturing a DNA fragment from a living organism. In either case, the DNA probe must be labeled with a molecular tag or beacon, such as a radioactive phosphorus atom (as is used for autoradiography ) or a fluorescent dye (as is used in fluorescent in situ hybridization, or FISH), so that the probe and the DNA it binds to can be seen ( [link] ). The DNA sample being probed must also be denatured to make it single-stranded so that the single-stranded DNA probe can anneal to the single-stranded DNA sample at locations where their sequences are complementary. While these techniques are valuable for diagnosis, their direct use on sputum and other bodily samples may be problematic due to the complex nature of these samples. DNA often must first be isolated from bodily samples through chemical extraction methods before a DNA probe can be used to identify pathogens.

A diagram of DNA probe. First a gene of interest is identified and cloned. Then single stranded probes are labeled with a molecular beacon. Finally, the DNA probe binds to complementary sequences in a DNA sample. The complementary sequences are single stranded DNA. The probe only attaches to one of the ssDNA sequences since it has the gene of interest in it
DNA probes can be used to confirm the presence of a suspected pathogen in patient samples. This diagram illustrates how a DNA probe can be used to search for a gene of interest associated with the suspected pathogen.

Part 2

The mild, flu-like symptoms that Kayla is experiencing could be caused by any number of infectious agents. In addition, several non-infectious autoimmune conditions, such as multiple sclerosis, systemic lupus erythematosus (SLE), and amyotrophic lateral sclerosis (ALS), also have symptoms that are consistent with Kayla’s early symptoms. However, over the course of several weeks, Kayla’s symptoms worsened. She began to experience joint pain in her knees, heart palpitations, and a strange limpness in her facial muscles. In addition, she suffered from a stiff neck and painful headaches. Reluctantly, she decided it was time to seek medical attention.

  • Do Kayla’s new symptoms provide any clues as to what type of infection or other medical condition she may have?
  • What tests or tools might a health-care provider use to pinpoint the pathogen causing Kayla’s symptoms?

Jump to the next Clinical Focus box. Go back to the previous Clinical Focus box.

Agarose gel electrophoresis

There are a number of situations in which a researcher might want to physically separate a collection of DNA fragments of different sizes. A researcher may also digest a DNA sample with a restriction enzyme to form fragments. The resulting size and fragment distribution pattern can often yield useful information about the sequence of DNA bases that can be used, much like a bar-code scan, to identify the individual or species to which the DNA belongs.

Gel electrophoresis is a technique commonly used to separate biological molecules based on size and biochemical characteristics, such as charge and polarity. Agarose gel electrophoresis is widely used to separate DNA (or RNA) of varying sizes that may be generated by restriction enzyme digestion or by other means, such as the PCR ( [link] ).

Questions & Answers

what is cell
Avi Reply
is unit of life
Kamaluddeen
Ok
mohamed
who is an industrial microbiologist
Cynthia Reply
I want to know the biochemical composition of bacteria
Josh Reply
It contains peptidoglcon, DNA nd RNA
Asiya
bacteriophage disadvantage
Momina Reply
disease due to __________ abnormalities are termed primary immunodeficiencies
Tayee Reply
Some primary immunodeficiencies are due to a defect of a single cellular or humoral component of the immune system.
Prince
Examples of primary immunodeficiencies include: chronic granulomatous disease, X-linked agammaglobulinemia, selective IgA deficiency etc
Prince
thank you
Nana
explain microbial mutation
Emerald
what is mutation
Cynthia Reply
alteration in genetic makeup
UDEME
Hi, I'm new here. I'm Bello Abdul Hakeem from Nigeria.
BELLO Reply
welcome on board
Kamaluddeen
Thanks brother I'm an undergraduate. I hope to study for MBBS.
BELLO
pls guys help me out
Linda
what is limitation of plate
Linda
limitation of plate load test . there are some that should be considered while performing load test which are given below, this test is usually performed on relatively similar plate ,usually 1 or 2 square foot area the reason is that the plate of greater are the economically not feasible
yemi
iam new here my name shafiu umar from Nigeria
Shafiu
thanks shafiu
gambo
how to differentiate Gram positive from Gram negative bacteria?
Faheem
by the cell membrane
Tim
with gram staining which has 4 steps
Freedom
Mechanism of bacterial pathogenicity
rashida Reply
Toxicity
Ibrahim
write a short note on Algea
najaatu Reply
green minutes plants organisms that are produced in turf.
Prince
Algae is a kind of a photosynthetic organism, which is usually grown in the moist areas. These are usually the simple plants that grow near to the water bodies. It contains a kind of chlorophyll pigments that act as a primary coloring agent.
Avi
they are eukaryotic and most lived in fresh water. they are photosynthetic that's, they contain chlorophyll and store starch in discrete chloroplast.
Prince
are bacteria important to man
just Reply
yes, depending on the type of bacteria .eg the normal florals, the latic acid batteries etc are important to man
Lois
I mean latic acid bacterial
Lois
I don't understand this topic
Jane Reply
what topic is that
Rose
sahi kon hai bhosri ke
saurabh Reply
define metabolism of carbohydrates with example
Thavasi Reply
what is sterilization a
Sani
the process of keep equipment free from bacteria
shar
is it only bacteria?
Lois
no undesirable fungi and contamination also.
Khushbu
what is streak plate method
Offikwu
what is the biofilm
Dimingu
metabolism is the sum of all the biochemical reaction required for energy generation and use of that energy to synthesize cell materials from small molecules in environment.
Alex
boclenia
Pooja
what are granulocytes
Shawnitta Reply
e.coli
Sukhdeep
granulocytes are type of WBCs which contains granules in the cytoplasm
Owili
what is mutation
Cynthia
it is the interchange of genes from their normal sequence
Esther
is an heritable change of the base-pair sequence of genetic material
Elizabeth
suitable example for prokaryotes
Suvetha Reply
one of the possible early sources of energy was
Suvetha
uv radiation and lighting
Anisha
e coli is the example of prokaryotes
Sukhdeep
archaea too
Noel

Get the best Microbiology course in your pocket!





Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Microbiology' conversation and receive update notifications?

Ask