Triplex DNA, TFOs, PNAs, RNA-DNA Hybrids and dsRNA/RNAi
In Chapter, we discussed the use of DNA probes for recognition of homologous nucleic acid sequences. These DNA probes have proved to be a valuable tool in molecular biology studies involving (i) in-gel hybridization (particularly for oligonucleotide fingerprinting using synthetic SSRs), (ii) Southern blots (particularly for RELPs, etc.) and (iii) Northern blots (for mRNA analysis). These techniques involving nucleic acid hybridization for recognition of complementary nucleic acid sequence have been a central feature of biotechnology, during the last quarter of the 20th century (1975-2000).

Triplex DNA, triplex forming oligonucleotides (TFOs) peptide nucleic acids (PNAs), chimeric RNA-DNA molecules and double stranded RNA (dsRNA) are some of these altered forms of nucleic acids, which proved useful in biotechnology research. In particular, a novel approach representing a dramatic departure from standard oligonucleotide chemistry, involves the use of peptide nucleic acids (PNAs), which differ from DNA and RNA in having a pseudo-peptide backbone. These novel nucleic acid molecules and their uses in biotechnology will be discussed in this chapter.