DNA Manipulation and Biotechnology Techniques

How Scientists Work with DNA

It always starts with the sequence. Once the sequence is known, specific regions can be isolated, cloned, amplified, and then used to help us.

Biotechnology Methods and Applications

Biotechnology is the use of technology to change the genetic makeup of living things for human purposes. Generally, the purpose of biotechnology is to create organisms that are useful to humans or to cure genetic disorders.

Biotechnology uses a variety of techniques to achieve its aims. Two commonly used techniques are gene cloning and the polymerase chain reaction.

The Four Steps of Gene Cloning

Gene cloning is the process of isolating and making copies of a gene. Gene cloning involves four essential steps:

1. Isolation: In isolation, an enzyme is used to break DNA at a specific base sequence. This is done to isolate a gene.
2. Ligation: During ligation, the enzyme DNA ligase combines the isolated gene with plasmid DNA from bacteria. (A plasmid is circular DNA that is not part of a chromosome and can replicate independently.) The DNA that results is called recombinant DNA.
3. Transformation: In transformation, the recombinant DNA is inserted into a living cell, usually a bacterial cell. Changing an organism in this way is also called genetic engineering.
4. Selection: Selection involves growing transformed bacteria to make sure they have the recombinant DNA. This is a necessary step because transformation is not always successful. Only bacteria that contain the recombinant DNA are selected for further use.

Polymerase Chain Reaction (PCR)

The Polymerase Chain Reaction (PCR) makes many copies of a gene or other DNA segment. This might be done in order to make large quantities of a gene for genetic testing. PCR involves three steps:

1. Denaturing: Denaturing involves heating DNA to break the bonds holding together the two DNA strands. This leaves two single strands of DNA.
2. Annealing: Annealing involves cooling the single strands of DNA and mixing them with short DNA segments called primers. Primers have base sequences that are complementary to segments of the single DNA strands. As a result, bonds form between the DNA strands and primers.
3. Extension: Extension occurs when an enzyme (Taq polymerase or Taq DNA polymerase) adds nucleotides to the primers. This produces new DNA molecules, each incorporating one of the original DNA strands.