[W]e are far from certain what a gene is... many of the confusions and misrepresentations of biology arise from mixing up different definitions of ge… - Denis Noble

In higher animals, the bits of DNA code that we lump together and call... a 'gene' are... broken up into segments... called 's'... separated by non-coding stretches of DNA, called 's'. The exon codes can be combined in various orders to produce a full protein code.

[T]here is no one-to-one correspondence between genes and biological functions. Strictly... to speak of a 'gene for x' is always incorrect.

[I]f a gene consists of three exons, a, b, and c, it could be read as a, b, c, ab, bc, ac, abc, and perhaps... as cba, ca, ba, each... code for a different protein. At present we do not know the rules...