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In the northern blot , another variation of the Southern blot, RNA (not DNA) is immobilized on the membrane and probed. Northern blots are typically used to detect the amount of mRNA made through gene expression within a tissue or organism sample.

Microarray analysis

Another technique that capitalizes on the hybridization between complementary nucleic acid sequences is called microarray analysis . Microarray analysis is useful for the comparison of gene-expression patterns between different cell types—for example, cells infected with a virus versus uninfected cells, or cancerous cells versus healthy cells ( [link] ).

Typically, DNA or cDNA from an experimental sample is deposited on a glass slide alongside known DNA sequences. Each slide can hold more than 30,000 different DNA fragment types. Distinct DNA fragments (encompassing an organism’s entire genomic library) or cDNA fragments (corresponding to an organism’s full complement of expressed genes) can be individually spotted on a glass slide.

Once deposited on the slide, genomic DNA or mRNA can be isolated from the two samples for comparison. If mRNA is isolated, it is reverse-transcribed to cDNA using reverse transcriptase. Then the two samples of genomic DNA or cDNA are labeled with different fluorescent dyes (typically red and green). The labeled genomic DNA samples are then combined in equal amounts, added to the microarray chip, and allowed to hybridize to complementary spots on the microarray.

Hybridization of sample genomic DNA molecules can be monitored by measuring the intensity of fluorescence at particular spots on the microarray. Differences in the amount of hybridization between the samples can be readily observed. If only one sample’s nucleic acids hybridize to a particular spot on the microarray, then that spot will appear either green or red. However, if both samples’ nucleic acids hybridize, then the spot will appear yellow due to the combination of the red and green dyes.

Although microarray technology allows for a holistic comparison between two samples in a short time, it requires sophisticated (and expensive) detection equipment and analysis software. Because of the expense, this technology is typically limited to research settings. Researchers have used microarray analysis to study how gene expression is affected in organisms that are infected by bacteria or viruses or subjected to certain chemical treatments.

a) A diagram of a microarray. First two different cells are grown in culture – in this case cancerous and healthy cells. Then RNA is isolated from each culture. Then reverse transciptase labeling produces cDNA with either a red fluorescent probe or a green fluorescent probe. In this case the cDNA from the cancerous cells is produced using red fluorescent probes and the cDNA from healthy cells is produced using green fluorescent probes. These are then hybridized onto a microarray – which looks like a glass slide with many etchings. B) The result on a computer compares all the genes that are active in the cells. Green regions indicate genes that are only expressed in heathy cells, red regions indicate genes that are only expressed in cancerous cells, yellow regions indicate genes that are expressed in both cancerous and healthy cells, and black regions indicate genes that are not expressed in either cell type.
(a) The steps in microarray analysis are illustrated. Here, gene expression patterns are compared between cancerous cells and healthy cells. (b) Microarray information can be expressed as a heat map. Genes are shown on the left side; different samples are shown across the bottom. Genes expressed only in cancer cells are shown in varying shades of red; genes expressed only in normal cells are shown in varying shades of green. Genes that are expressed in both cancerous and normal cells are shown in yellow.
  • What does a DNA probe consist of?
  • Why is a Southern blot used after gel electrophoresis of a DNA digest?

Questions & Answers

what is prokaryotes
PRALHAD Reply
are micro-organisms that have no nucleus e.g bacteria
Foster
and they do not possess membrane bound organelles e.g mitochondria
Bharat
yes
Foster
they are single cellular organisms,
Rajasekhar
all the organelles are embedded in cytoplasm of the cell
Rajasekhar
They don't possess true nucleus
PREMI
they're unicellular organisms
Kamaluddeen
they are classified as bacteria and. archaea. bacteria have a cell membrane conposed of peptidoglycan and archaea is composed of psuedomu
Tara
pseudomurein
Tara
organelles are non membraneous as the nucleus
Tara
What is the biosynthesis of a bacteria cell
Adesina Reply
biosynthesis is multiple step enzymes catalyze process which occur in bacterial cell
Jayeeta
biological way of manufacturing food and utilizes it for growth, multiplication and development
Kamaluddeen
prokaryot
PRALHAD
what is microbiology
Kiirya Reply
which organism can not be seen necked eyes is knowm as microbiology
meet
microorganisms
Jayeeta
micro can be define as d smallest living organisms dat can not be see wit naked eyes only with the aid of a microscope 🔬
muhammed
bio means life logy means study
muhammed
biology can b define as the systematic study of living things
muhammed
microbiology can be define as the study of tiny organisms, that's according to my understanding
muhammed
Microbiology is the study of living organisms which cannot be seen by the naked eye but only with the aid of a microscope. These microorganisms can be classified as bacteria, fungi, micro-algae, protozoa and virus.
Tatz
microbes that can't seen in naked eyes. upto 100micrometer we can see in naked eyes but 1 microns or nanometers are invisible in naked eye.
Jayeeta
what is a cell
Oteri Reply
cell can be define as smallest indivisible organism in the body
muhammed
cell is the smallest unit which makes up the whole body
Yue
cell is smallest unit and there are two types prokaryotic cell and eukaryote cell. bacteria a prokaryotic cell which works independently.
Jayeeta
nice forum
muhammed
Which parasite competes with the host for vitamin B12 to cause pernicious anaemia
Abubakar
Diphyllobothrium latum for vit B12
Jayeeta
it is also fish tapeworm
Jayeeta
Diphyllobothrium sp feed vitB 12
Jayeeta
recent trends in microbiology of biofertilizer
Ykomalipriya Reply
using nano technology
Jayeeta
what is transposors
EMMANUEL Reply
Junk DNA, jumping gene.
Pradeep
transposon elements are jumping gene as DNA sequence move from one location to anothet
Jayeeta
Yes
Pradeep
what is microbiology
Usama Reply
Microbiology is the study of organisms, most of which are too small to be seen with the naked eye, including bacteria, algae, protozoa, and fungi, as well as acellular agents, such as viruses and prions.
digvijaya
what is gram +ve and gram - ve bacteria?
Sharma
gm- contain lipid layer so it take counter stain during gram staining and pink or red in color but gm + does have thick LPS layer.
Jayeeta
what year microbiology started
Kartik
Robert Koch was the first to detect microorganisms
Jayeeta
what appears microorganisms
Kartik
clear the questions please
Jayeeta
was it robert koch or robert hooke?
digvijaya
microbiology word came from microns. study microbes that not recognize in naked eyes.
Jayeeta
what are the branch of microbiology
Oyemade Reply
We can basically classify into pure and applied microbiology
Ozzie
what is arabinose operon and it's stucture
Pooja Reply
The L-arabinose operon, also called the ara or araBAD operon, is an operon required for the breakdown of the five-carbon sugar, L-arabinose, in Escherichia coli
Tharra
kya hum operon ko divide kar skate hain
Kartik
reactions if viruses to physical and chemical agents?
VICTOR Reply
All viruses contain the following two components: 1) a nucleic acid genome and 2) a protein capsid that covers the genome. Together this is called the nucleocapsid. In addition, many animal viruses contain a 3) lipid envelope. The entire intact virus is called the virion.
Asali
assume you have performed a gram stain on a sample of pus from a patients urethra. you see red, nucleated cells and purple rods. what can you conclude
Petty Reply
bacteria
ABUBAKAR
gram negative bacteria hence gonococcal infection
Kiirya
Study of micro organisation which we cannot see with naked eye...
shyam Reply
Despite their bad reputation, microbes are mostly beneficial or have a neutral effect on our lives. Microbiology is the scientific study of these microorganisms. Microorganisms are those organisms that are too small to see with the naked eye and include things like bacteria, fungi, and viruses.
Asali
yes
Dhirender
not 'things'...'organisms' like bacterias, viruses and fungi
Sinmi
simi, it's not bacterias but bacteria which is the plural form of the word while bacterium is the singular of it
Richard
bacterium is obvio in a singular form but plural of bacterium is bacterias
Sinmi
Richard is right it's bacterium which is the singular form and plural is bacteria. *Bacterias* doesn't exist.
Aakriti
that is microbiology which is deals with microbes only their structure
Kiirya
what is microbiology?
Sandeep Reply
what is microbiology
Glory
is the study of small microorganisms that can't be viewed by our naked eyes under a microscope
Nabukwasi
it's the study of microbes their classification, diversity, their cellular structure and processes, their applications and interaction with other organisms.
Chaitanya
what is EMP pathway
rajesh
which organism is implicated in meningoencephalitis
Peter Reply
Herpes virus
Carlos
Yeah
Laxmi
which mold is called dairy mold?
Gopinath
mushroomm
Top
Geotrichum candidum
Gopinath
hi
bio
Hlw
Laxmi
which infectious agent is the smallest
Sinmi
spore or virus
Anushree
prion ....it is a single protein in a misfolded form..there is also a theory based on it
Sinmi
yup...m sry
Anushree
yes it can be turned as a virus
Sinmi
which gram positive bacteria is responsible for food poisoning?
Sinmi
prion is not a living organism yet it is infectoois why
Jeevan
prions are virus like organism. and it is a misfolded protein that may cause disease to us.
Tharra
Clostridium perfringens, B.cereus
Sneha
Who is the father of the biology
Dhirender
I have one more question. . that who is the father of botany and medicine? ? can any one tell
Dhirender
define polar bond in simple way
Rashmi Reply
when there is formation of positive and negative poles i.e. one atom is +ve and other is -ve which further results in the dipole moment. Such bond is know as polar bond. It is a convalent bond only.
Aakriti

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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