Genome content estimation

The two ways genome content may be reported are in absolute amounts and in arbitrary units. When expressing genome size in absolute terms, various units may be employed. The most common unit is pico-grams (1 pg is equal to 10 12 g). Other units that may be used are daltons and nucleotide pairs. One is able to convert from one unit to another based on the following equations 1 nucleotide pair = 660 daltons, and 1 pg = 0.965 X 109 nucleotide pairs. It should be noted that these conversions are only estimates and should be considered accordingly. 

For theTrematoda and Cestoda, both reassociation kinetics/Cot analysis and direct measurement of the DNA content of Feulgen-stained nuclei have been used to estimate genome size. As relatively few taxa have been examined, it is difficult to draw any firm conclusions although the available data suggest much less extreme variation than in the Turbellaria and the absence of step-like intrageneric variation (Table 2.3). 

The scope of the PTG is best appreciated when juxtaposed to the contents of the entire human genome. To date, in addition to the two complementary versions of the genome published in 2001 [34, 35], completed sequence has been published to date for six of the autosomes [46, 54—58]. Current best estimates suggest that the human genome contains 35000 to 50000 genes. Our PTG, therefore, represents approximately 15% of all human genes. 

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