Chargaff's Rules

Source
mol % of bases
Ratios
%GC

A
T
G
C
A/T
G/C

PhiX-174
24.0
31.2
23.3
21.5
0.77 ¦
1.08
44.8

Maize
26.8
27.2
22.8
17.0 *
0.99
0.98
46.1

Octopus
33.2
31.6
17.6
17.6
1.05
1.00
35.2

Chicken
28.0
28.4
22.0
21.6
0.99
1.02
43.7

Rat
28.6
28.4
21.4
20.5
1.01
1.00
42.9

Human
29.3
30.0
20.7
20.0
0.98
1.04
40.7

* Plant DNA is an apparent exception to Chargaff's rules, however, plant DNA is often heavily methylated. As long as the amount of 5-methyl-cytosine is included in the total amount of cytosine, the rules are obeyed.

¦ Some bacteriophage DNA's (e.g. PhiX174) do not adhere to Chargaff's rules - these phages have single-stranded genomes and are therefore not constrained by the requirements of a double-stranded structure.

Adapted from http://www.mun.ca/biochem/courses/3107/Topics/DNA_history.html.

Source	mol % of bases				Ratios		%GC
Source	A	T	G	C	A/T	G/C	%GC
PhiX-174	24.0	31.2	23.3	21.5	0.77 ¦	1.08	44.8
Maize	26.8	27.2	22.8	17.0 *	0.99	0.98	46.1
Octopus	33.2	31.6	17.6	17.6	1.05	1.00	35.2
Chicken	28.0	28.4	22.0	21.6	0.99	1.02	43.7
Rat	28.6	28.4	21.4	20.5	1.01	1.00	42.9
Human	29.3	30.0	20.7	20.0	0.98	1.04	40.7