The substem -virsen designates antiviral antisense oligonucleotides. Nucleic acids function to trap mRNA, DNA, rRNA, and other nucleic acids/oligonucleotides. The common stem for antisense oligonucleotides is -rsen. The maximum length of synthetic oligonucleotides hardly exceeds 200 nucleotide residues. In addition, recombination with single-strand oligonucleotides (oligos) was first shown in Saccharomyces cerevisiae. Synthetic biomolecules such as oligonucleotides may also be used as analytes. The maximum length of synthetic oligonucleotides hardly exceeds 200 nucleotide components. DNA microarrays are a useful analytical application of oligonucleotides. This involved two closely related methods that generated short oligonucleotides with defined 3' termini. Yet another technique termed molecular beacons makes use of synthetic fluorescein-labeled oligonucleotides. PS backbone modifications to oligonucleotides protects them against unwanted degradation by enzymes. The mutation problem could be solved by shorter oligonucleotides used to assemble the gene. Creating chemically stable short oligonucleotides was the earliest challenge in developing ASO therapies. Next the top strand of the gene is divided into small degenerate oligonucleotides. Synthesis of OPS is very similar to that of natural oligonucleotides.