How to label oligonucleotides internally?

There are many ways to label or modify oligonucleotides. Sequence modifier molecules are designed for use in automated solid phase oligonucleotide synthesis. Amino-modifier can be added or placed within an oligonucleotide sequence as their phosphoramidites. After deprotection of the synthetic product, the primary amine on the modifier group can be labelled with various molecules, including fluroescent dyes or enzymes.

Oligonucleotides can be labeled or modified with a modifier moiety placed "in between" the sugar-phosphate backbone or by using a functional group already present "on the base" itself.

Dyes or other molecules, such as peptides, can be connected or conjugated to oligonucleotides containing the modifier moiety post-synthetically.