A process for determining the sequence of nucleic acids of interest employs nucleotides or nucleotide analogs that have been made detectable by non-radioactive modifying or labeling. Such nucleotides or nucleotide analogs are modified on the sugar moieties, the phosphate moieties or the base moieties, including base analogs. Modified nucleotide analogs can be attached to or coupled to or incorporated into DNA or RNA. The modified or labeled nucleotides or nucleotide analogs are also useful in processes for detecting the presence of nucleic acids of interest and for characterizing chromosomal sequences. Detection processes using the modified or labeled nucleotides or nucleotide analogs extend to the use of a gel for separating or resolving hybrids formed between non-radioactively labeled oligonucleotides or polynucleotides and such nucleic acids of interest.