Genome Size or C Value

The C value is the amount of DNA in a haploid complement. Currently, the amount is reported as the total number of base pairs. Generally, more complex organisms have more DNA. For example, the haploid complement of Homo sapiens DNA contains between 3.12 and 3.2 gigabases (the prefix "giga" denotes billions), while the haploid complement of yeast (Saccha-romyces cerevisiae) DNA contains 12,057,500 base pairs.

Unexpected genomic sizes occur, however, in a condition called the C value paradox. Two closely related species can have widely divergent amounts of DNA. For example, Paramecium caudatum has a C value of 8,600,000 kilobases (where the prefix "kilo" denotes thousands) while its near relative P. aurelia has a C value of just 190,000 kilobases. Another paradoxical circumstance occurs when a simpler organism has a C value higher than a more complex organism. For example, Amphiuma means (a newt) and Amoeba dubia (an amoeba) have, respectively, C values that are 26 and 209 times the C value of humans.

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