ASSIGNMENT 1: PROPERTIES OF DNA/RNA

Introduction:

The polymerase chain reaction is an innovative technology, which amplifies a single piece of DNA across several orders of magnitude. The end result is the creation of thousands to millions of copies of a particular DNA sequence.

PCR is closely patterned after the natural principle of DNA replication. It is a three-step process, referred to as a cycle, that is repeated a specified number of times. One PCR cycle consists of the following steps:

* Denaturation * Annealing * Extension

This process takes place in a thermal cycles, usually between 30 and 40 cycles.

In the initial step, heat (usually hotter than 90 degrees Celsius) separates double-stranded DNA into two single strands. This process is called "denaturation." Denaturation is possible because the hydrogen bonds linking the bases to one another are weak. The hydrogen bonds break at high temperatures, whereas the bonds between deoxyribose and phosphates, which are stronger covalent bonds, remain intact.

The goal of PCR is not to replicate the entire strand of DNA but to replicate a target sequence of approximately 100-600 base pairs unique to the organism being studied.

Targeting the sequence is achieved by using primers. They are specific for the target region of the organism.

Two primers are included in the PCR, one for each of the complementary single DNA strands that was produced during denaturation. The primers that anneal or in other words bind to the complementary sequence mark the beginning of the DNA target sequence of interest. With regard to temperature, annealing usually takes place between 40 degrees Celsius and 65 degrees Celsius, depending on the length and base sequence of the primers. This allows the primers to anneal to the target sequence with high specificity.

Once the primers anneal to the