Nucleic acid hybridisation and Nucleic acid probes Essay

Nucleic acid hybridisation and Nucleic acid probes - Essay Example For instance, if a DNA strand with a desired nucleotide sequence is to be detected from a mixture of many other strands, an oligonucleotide containing a few complementary bases to the desired sequence can be prepared and attached to an anchor such as a membrane or a paper. When soaked in a solution having a mixture of many strands, the one, which is complementary to the oligonucleotide, will bind to it through complementary base pairing, also known as â€Å"zippering† (Lodish et al, 2004, p. 11). When double stranded DNA is heated in a dilute salt solution, its two strands separate because of the breakdown of complementary base pairing (melting). This strand separation is called denaturation. The temperature at which the two complementary strands separate is called the melting temperature ‘Tm’, and is affected by the percentage of G.C base pairs, ion concentration of the solution, presence of destabilising compounds like urea, and the pH of the solution (Lodish et al, 2004, p. 105). A particular fragment of DNA or RNA whose nucleotide sequence is complementary to a gene or nucleotide of interest is called a nucleic acid probe. A nucleic acid probe has to be designed in such a way that it hybridises through complementary base pairing to the target DNA or RNA that has to be detected. It should be long enough (about 20 nucleotide long) to pair exclusively to the target nucleotide sequence. Probes are labeled with radioactive tracers, histochemical compounds or fluorescent dyes to enable their detection from a heterogeneous mixture of nucleic acids (Nussbaum et al, 2004, p.41). For instance, 32P labeled probes are developed using polynucleotide kinase that transfers a