Search engine: A software program that searches a database and gathers and reports information that contains or is related to specified terms.

Similarity (homology) search: Given a newly sequenced gene, there are two main approaches to the prediction of structure and function from the amino acid sequence. Homology methods are the most powerful and are based on the detection of significant extended sequence similarity to a protein of known structure, or of a sequence pattern characteristic of a protein family. Statistical methods are less successful but more general and are based on the derivation of structural preference values for single residues, pairs of residues, short oligopeptides or short sequence patterns. The transfer of structure/function information to a potentially homologous protein is straightforward when the sequence similarity is high and extended in length, but the assessment of the structural significance of sequence similarity can be difficult when sequence similarity is weak or restricted to a short region.

Splicing: The joining together of separate DNA or RNA component parts. For example, RNA splicing in eukaryotes involves the removal of introns and the stitching together of the exons from the pre-mRNA transcript before maturation.

Selfish genetic element: A very diverse and common feature of eukaryotic genomes, such as transposons.

Self-splicing intron: An intron that can be cleaved out of the pre-mRNA without the aid of an internal catalyst.

Signal peptide: A short sequence at the N-terminus of some proteins that directs the protein across a membrane.

Splice junction mutation: A mutation that alters a junction between an intron and an exon so that it no longer functions properly.

Splice site: Location in the DNA sequence where RNA removes the noncoding areas to form a continuous gene transcript for translation into a protein.

Stop codon: One of the three codons that marks the position where translation of an mRNA should stop.

Structural domain: A segment of a polypeptide that folds independently of other segments.