Table V.

Average GC levels and cesium chloride buoyant densities in maize, Arabidopsis, C. reinhardtii, and P. tricornutum

Species	CDS, GCs	CDS, GC1	CDS, GC2	CDS, GC3	Buoyant Density of DNA	Total DNA, GC
	%				g cm−3	%
C. reinhardtii	64.3	60	40	90	1.723a, 1.7218b	62.1c, 63.1d
Maize	60.3	60	40	70e	1.7021	47.0
P. tricornuum	53.7	55	40	65	1.7075	48.5
Arabidopsis	46.4	50	40	45	1.695	35.7

GC levels of total DNA were obtained by calculation of GC level at the peak of the cesium chloride profiles. In the case of maize, we used the value reported by Carels et al. (1995).

^a Buoyant densities from C. reinhardtii were taken from Chiang and Sueoka (1967). 

^b Buoyant densities from C. reinhardtii were taken from our results. 

^c Corresponding GC levels were taken from Sager and Ishida (1963). 

^d Corresponding GC levels were calculated from our measurements of the DNA buoyant density using Schildkraut's formula (Schildkraut et al., 1962). 

^e The average GC₃ level is inappropriate for comparison in maize because two classes of genes must be taken into consideration (Carels and Bernardi, 2000). The values previously reported are 68.6% for GC-poor genes and 89% for GC-rich genes. However, the value for GC-poor genes is biased by the small size of the sample and is more likely to be around 50% to 55% GC₃ (see Fig. 3).