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By the end of this section, you will be able to:
  • Describe gel electrophoresis
  • Explain molecular and reproductive cloning
  • Describe uses of biotechnology in medicine and agriculture

Biotechnology is the use of biological agents for technological advancement. Biotechnology was used for breeding livestock and crops long before the scientific basis of these techniques was understood. Since the discovery of the structure of DNA in 1953, the field of biotechnology has grown rapidly through both academic research and private companies. The primary applications of this technology are in medicine (production of vaccines and antibiotics) and agriculture (genetic modification of crops, such as to increase yields). Biotechnology also has many industrial applications, such as fermentation, the treatment of oil spills, and the production of biofuels ( [link] ).

The left side of this image is an old black and white photo of a mailbox plastered with an advertisement reading “Penicillin cures gonorrhea in four hours. See your doctor today.” The right side of the image shows a petri dish streaked with bacteria. Bacteria grow everywhere on the plate except where discs containing antibiotic have been placed. These areas are completely devoid of bacterial growth
Antibiotics are chemicals produced by fungi, bacteria, and other organisms that have antimicrobial properties. The first antibiotic discovered was penicillin. Antibiotics are now commercially produced and tested for their potential to inhibit bacterial growth. (credit "advertisement": modification of work by NIH; credit "test plate": modification of work by Don Stalons/CDC; scale-bar data from Matt Russell)

16.1a basic techniques to manipulate genetic material (dna and rna)

Dna and rna extraction

To study or manipulate nucleic acids, the DNA or RNA must first be isolated (extracted) from the cells. Various techniques are used to extract different types of DNA ( [link] ). Most nucleic acid extraction techniques involve steps to break open the cell and use enzymatic reactions to destroy all macromolecules that are not desired (such as degradation of unwanted molecules and separation from the DNA sample). Cells are broken using a lysis buffer     (a solution which is mostly a detergent); lysis means “to split.” These enzymes break apart lipid molecules in the cell membranes and nuclear membranes. Macromolecules are inactivated using enzymes such as proteases     that break down proteins, and ribonucleases     (RNAses) that break down RNA. The DNA is then precipitated using alcohol. Human genomic DNA is usually visible as a gelatinous, white mass. The DNA samples can be stored frozen at –80°C for several years.

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.

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.

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Source:  OpenStax, General biology part i - mixed majors. OpenStax CNX. May 16, 2016 Download for free at http://legacy.cnx.org/content/col11749/1.5
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