Table 1.

Most frequent pairs of functional classes between adjacent genes within operons, and between those at transcription unit boundaries

Pairs in operons		Pairs not in operons
Functional classes	No. of pairs	Functional classes	No. of pairs
2.72/2.72	37	6/51	5
50.3/50.3	32	40.1/40.1	5
40.1/40.1	28	53/58.5	3
53/53	22	50.3/50.3	3
2.71/2.71	22	40.1/40.5	3
52/52	18	1.1/53	3
1.1/1.1	17	1.1/2.72	3
51/51	16	1.1/1.1	3
1.1/53	13	9.81/53	2
6/6	9	60.3/60.3	2

Functional classes have a designated number as provided by Monica Riley. The numbers in this table mean: 1.1, Carbon compounds; degradation of small molecules; metabolism of small molecules. 2.71, aerobic respiration; energy metabolism, carbon; metabolism of small molecules. 2.72, anaerobic respiration; energy metabolism, carbon; metabolism of small molecules. 6, global regulatory functions; global functions. 9.81, isoleucine; amino acid biosynthesis; metabolism of small molecules. 40.1, ribosomal proteins–synthesis, modification; ribosome constituents; structural elements. 40.5, DNA–replication, repair, restriction/modification; macromolecule synthesis, modification. 50.3, surface structures; cell exterior constituents; structural elements. 51, amino acids, amines; transport of small molecules; cell processes. 52, cations; transport of small molecules; cell processes. 53, carbohydrates, organic acids, alcohols; transport of small molecules; cell processes. 58.5, osmotic adaptation; adaptation; processes. 60.3, colicin-related functions; laterally acquired elements; elements of external origin.