Table 2. Architectural features of different species' sequences.

	G + C content*
Species	Total	Nonrepetitive sites	Synonymous 4D sites	Relative size†	Percentage repetitive‡
Human	0.384	0.369	0.432	NA	40.3
Cat	0.383	0.372	0.434	0.95	36.4
Pig	0.377	0.366	0.455	0.92	31.9
Mouse	0.401	0.391	0.479	0.90	32.6
N.A. opossum	0.358	0.358	0.415	1.17	43.2
S.A. opossum	0.358	0.358	0.380	0.99	34.2
Wallaby	0.373	0.374	0.412	1.15	37.0
Platypus	0.459	0.457	0.642	0.76	44.9
Chicken	0.412	0.407	0.423	0.44	6.0
Fugu	0.486	0.485	0.721	0.16	2.3

Boldface indicates the data for noneutherian mammals.

^*Fraction of G + C bases in the entire sequence (total), the nonrepetitive portion of sequence (i.e., sequence not masked by repeatmasker), and synonymous 4D sites (the third position of codons that can be any base and still code for the same amino acid)

^†Ratio of sequence length in each species to the amount of corresponding human sequence (as defined in Table 1)

^‡Percentage of sequence masked by repeatmasker