Practice question

Nucleic acid probes must balance specificity, hybridization kinetics, and tissue penetration. Probes shorter than about 15 nucleotides lack sequence complexity and hybridize non-specifically to multiple sites, while excessively long probes exhibit slow reassociation, poor membrane transfer, and limited cellular penetration. Optimal oligonucleotide probes range approximately 20 to 100 nucleotides, providing sufficient uniqueness to recognize single-copy sequences in complex eukaryotic genomes while maintaining high melting temperature and stable duplex formation. This size range enables rapid hybridization, good signal-to-noise ratio, and compatibility with Southern blotting, Northern blotting, and fluorescence in situ hybridization.