Typically protein coding segments are found in the open reading frames of exons, though alternative splicing and other epigenetic modifications account for much of the complexity of the genome.
A gene class can be defined as a group of genes with related functions, or by biologically relevant information. For example, a class could be defined by a signal transduction or metabolic pathway, by the members of a protein complex, or by an enzymatic activity. So, a gene can be a member of any number of classes, and hundreds if not thousands of gene classes can be defined on the basis of function.
Class II genes code for proteins and are transcribed by RNA polymerase II. The promoter region of Class II genes often contains a TATA box, and their basal transcription requires formation of a preinitiation complex.
In general, a consensus sequence is that idealized sequence in which each position represents the base/amino acid most often found when many sequences are compared. A genetic consensus sequence is a sequence of nucleotides that is common to different genes or genomes. There may be some variations but such sequences show considerable similarity. So, a consensus sequence is the prototype sequence that most others approach.
See also: enhancer : exon : genome : gene regulation : genetic template : Group I and II introns : insulator : open reading frame : promoters : repressor : regulatory sequence : silencers : spliceosome : template :