Studying and Manipulating Genomes
In 1953, the invention of the structure of DNA stimulated intense interest in inventing technologies to manipulate that structure. The whole human genome had been sequenced 50 years later. DNA can be cut by restriction enzymes and the fragments combined to form recombination DNA. Copies of DNA can be produced inside living cells or by using PCR, or the polymerase chain reaction. Variations in DNA sequences can be judged by DNA fingerprinting and by automated DNA sequencing. Typical or converted genes can be inserted into organisms for research and practical applications. Genetically converted and "transgenic" organisms are used to produce food, bio-materials, and pharmaceuticals. Information about the human genome is being worn for gene therapy and other applications. Many ethical and social issues remain a mystery and objections to the use of genetic engineering persist.
Cloning a Gene in Bacteria
We can use the processes of DNA technology to recombine and copy genes. A restriction enzyme is used to cut open a plasmid, a small circular DNA molecule obtained from a bacterium. The plasmid provides as a cloning vector. The restriction enzyme cuts only at a certain DNA base sequence, called a restriction site. The same enzyme is used to cut up DNA obtained from a human cell. The restriction enzyme makes DNA fragments that have identical sticky ends that connect by complementary base pairing. An enzyme called DNA ligase forges covalent bonds that connect human and plasmid DNA, forming recombinant DNA. The human gene is placed in the middle of the plasmid lacZ gene. The plasmid carries a gene for resistance to the antibiotic ampicillin. The human gene must be cloned to makes copies for use or study. A bacterium is convinced to carry on the recombinant plasmid from the surrounding solution in a process called transformation. A bacterium is left on a growth medium. It replicates the plasmid at the same times as its own DNA. Its products form a clone of bacteria that all have copies of the recombinant plasmid. The ampicillin in the medium shortens growth only to plasmid-containing cells. Bacteria without human genes have intact lacZ genes; this allows them to break down a substance in the medium that strains their colonies blue. The bacteria with human genes are in the colorless colonies.
Recombinant DNA Technology: Introducing a Gene into a Cell
DNA is found within the nucleus of most type of cells. It holds the instructions for a cell and determines what an organism looks like and how it processes. A member of DNA that codes for a certain trait or characteristic is called gene. A gene consists of chemical bases, or nucleotides, with 4 possible ones. They are Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). Their order in the DNA is what codes for the information. A always pair with T and C with G because they have specific shapes. In order to isolate a gene, extract the cell's DNA. A gene can be introduced into a cell using a vector. A plasmid can be used as a vector. The plasmid has to be extracted from the bacterium before you can use it as a vector. Now, isolate the gene that we want from the DNA and use restriction enzymes. The plasmid must be exposed to the same restriction enzyme, so that a gap in the circular DNA opens to get together with a new piece of DNA. The restriction enzyme cuts the same area on both molecules. Each end has a single-stranded DNA, called "sticky ends." Now, recombine the plasmid and the gene. The "sticky ends" base pair with any DNA molecule with complimentary "sticky ends." Ligase links the two into a molecule of recombinant DNA. The recombinant DNA piece contains the new gene, which is introduces into a plant cell. The process is called transformation, which has several transnational methods that can be used to meet a gene into a cell. When the desired gene is transferred into the cell, it replicates and divides. The new cells contain the inserted gene.