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This illustration shows the four main steps of DNA extraction. In the first step, cells in a test tube are lysed using a detergent that disrupts the plasma membrane. In the second step, cell contents are treated with protease to destroy protein, and RNAase to destroy RNA. The resulting slurry is centrifuged to pellet the cell debris. The supernatant, or liquid, containing the DNA is then transferred to a clean test tube. The DNA is precipitated with ethanol. It forms viscous, mucous-like strands that can be spooled on a glass rod
This diagram shows the basic method used for extraction of DNA.

RNA analysis is performed to study gene expression patterns in cells. RNA is naturally very unstable because RNAses are commonly present in nature and very difficult to inactivate. Similar to DNA, RNA extraction involves the use of various buffers and enzymes to inactivate macromolecules and preserve the RNA.

Gel electrophoresis

Because nucleic acids are negatively charged ions at neutral or basic pH in an aqueous environment, they can be mobilized by an electric field. Gel electrophoresis is a technique used to separate molecules on the basis of size, using this charge. The nucleic acids can be separated as whole chromosomes or fragments. The nucleic acids are loaded into a slot near the negative electrode of a semisolid, porous gel matrix and pulled toward the positive electrode at the opposite end of the gel. Smaller molecules move through the pores in the gel faster than larger molecules; this difference in the rate of migration separates the fragments on the basis of size. There are molecular weight standard samples that can be run alongside the molecules to provide a size comparison. Nucleic acids in a gel matrix can be observed using various fluorescent or colored dyes. Distinct nucleic acid fragments appear as bands at specific distances from the top of the gel (the negative electrode end) on the basis of their size ( [link] ). A mixture of genomic DNA fragments of varying sizes appear as a long smear, whereas uncut genomic DNA is usually too large to run through the gel and forms a single large band at the top of the gel.

Photo shows an agarose gel illuminated under UV light. The gel contains nine lanes from left to right. Each lane was loaded with a sample containing DNA fragments of differing size that separated as they travelled through the gel from top to bottom. The DNA appears as thin, white bands on a black background. Lanes one and nine contain many bands from a DNA standard. These bands are closely spaced toward the top, and spaced farther apart further down the gel. Lanes two through eight contain one or two bands each. Some of these bands are identical in size and run the same distance into the gel. Others run a slightly different distance, indicating a small difference in size.
Shown are DNA fragments from seven samples run on a gel, stained with a fluorescent dye, and viewed under UV light. (credit: James Jacob, Tompkins Cortland Community College)

Amplification of nucleic acid fragments by polymerase chain reaction

Although genomic DNA is visible to the naked eye when it is extracted in bulk, DNA analysis often requires focusing on one or more specific regions of the genome. Polymerase chain reaction ( PCR ) is a technique used to amplify specific regions of DNA for further analysis ( [link] ). PCR is used for many purposes in laboratories, such as the cloning of gene fragments to analyze genetic diseases, identification of contaminant foreign DNA in a sample, and the amplification of DNA for sequencing. More practical applications include the determination of paternity and detection of genetic diseases.

Illustration shows the amplification of a DNA sequence by the polymerase chain reaction. PCR consists of three steps—denaturation, annealing, and DNA synthesis—that occur at high, low, and intermediate temperatures. In step 1, the denaturation step, the sample is heated to a high temperature so the DNA strands separate. In step 2, annealing, the sample is cooled so two primers can anneal to the two strands of DNA. The primers are spaced such that the sequence of interest between them will be amplified. In step 3, DNA synthesis, the sample is warmed to the optimal temperature for Taq polymerase, which synthesizes the complementary strand from the primer to the 3' end of the molecule. This cycle is repeated again and again. Each time, the newly synthesized strands serve as templates so that the amount of DNA doubles with each cycle. As the cycles continue, more and more strands are the size of the distance between the two primers; in the end, the vast majority of strands are this size.
Polymerase chain reaction, or PCR, is used to amplify a specific sequence of DNA. Primers—short pieces of DNA complementary to each end of the target sequence—are combined with genomic DNA, Taq polymerase, and deoxynucleotides. Taq polymerase is a DNA polymerase isolated from the thermostable bacterium Thermus aquaticus that is able to withstand the high temperatures used in PCR. Thermus aquaticus grows in the Lower Geyser Basin of Yellowstone National Park. Reverse transcriptase PCR (RT-PCR) is similar to PCR, but cDNA is made from an RNA template before PCR begins.

Questions & Answers

what is biology mean?
Nickey Reply
bio means life logy means study . study about life . physiology. morphology . anatomy and others organisms related topics is termed as biology
Darshan
Biology is the study life. that the study about living organism
SIRAJO
what is oxidation?
Rose Reply
 the state or result of being oxidized
Emmanuel
hahahaha thanks, but my teachers requires a thorough meaning about that
Rose
Is the process of oxidizing ,the addition of oxygen to a compound with a loss of electrons, always accompanied by reduction
Korletey
loss of electron....
Anwar
thank you. 😊
Rose
thank you. 😊
Rose
thank you. 😊
Rose
what is oxidized
Oyebanji
the process or result of oxidizing or being oxidized.
Jersey
my pleasure
Anwar
Google itttt.....if need explanation
Anwar
to rose...
Anwar
oxidation is the removal of oxygen addition of hydrogen
SIRAJO
what is genetic
Chibawa Reply
name the enzymes that i found in the saliva
Valuables Reply
draw a bacterium cell and label
Kadijah Reply
What are the osmoregulatory functions of the kidney?
bisi Reply
filter
Meenu
What is ecology
Hebert Reply
what is cell
Etama Reply
cell is the basic unit of life
Asiatou
cell is the basic structural and functional unit of an living organism
Darshan
a cell is the smallest and most basic unit of a living thing
John
cell is the basic unit of life. we are made up of 60,000 billions of cells.Each cell carry out a specific function in the body.
Pallavi
A cell is the smallest basic functioning unit of life.
Ali
where is the pectoral gridle located?
Tiania Reply
What is hypotonic
Bright Reply
what is hypotonic
Dangaya
Hypotonic means weak solution
Ali
the difference between the two cells
Obeng Reply
explain the courses and the correction of lon term sightedness and short term sightedness
Isaac Reply
long sightedness is said to be like someone that can see far object clearly why short sightedness is someone that only can see near obect
SHEDRACK
why drinking excess alcohol causes thirst and dehydration
uwikuzo Reply
Can we chat about nutrition please?
Elia
yes
Uzair
sure
Uzair
Uhm why is it so important to follow the nutritional process?
Elia
BC it contribute to the source of life
SHEDRACK
what is reproduction
smart Reply
it is d act of bringing young ones to life
Oyebanji
to ensure survival of a species🚴‍♀️
Michelle
what is a genotype
Collins
what is hazardous
smart
a cell is the smallest unit of a living thing. so we all have cell
smart
It is the formation of a zygote resulting from the fusion of the sperm cell with the ovum.Thus,this results in the production of new species which are genetically dissimilar from their parent cells.
Pallavi
yes we all have cell round our body without the existances of cell them they will be no life in us as human
SHEDRACK
what is size of cell
Mohd Reply
what is size of Hart
Mohd
nanometers=um sign thingie
Michelle
microns=nanometers
Michelle

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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