Genomics
One of the most striking features is the large amount of cellular DNA that dinoflagellates contain. Most eukaryotic algae contain on average about 0.54 pg DNA/cell1, whereas estimates of dinoflagellate DNA content range from 3–250 pg/cell, corresponding to approximately 3000–215 000 Mb (in comparison, the haploid human genome is 3180 Mb and hexaploid Triticum wheat is 16 000 Mb). It has been suggested that polyploidy or polyteny may account for this large cellular DNA content, but studies of DNA reassociation kinetics do not support this hypothesis.
In addition to their disproportionately large genomes, dinoflagellate nuclei are unique in their morphology, regulation, and composition.
The dinoflagellates share an unusual mitochondrial genome organisation with their relatives, the Apicomplexa. Both groups have very reduced mitochondrial genomes (~6 kilobases in the Apicomplexa). The genes on the dinoflagellate genomes have undergone a number of reorganisations, including massive genome amplification and recombination which have resulted in multiple copies of each gene and gene fragments linked in numerous combinations. Loss of the standard stop codons, trans-splicing of mRNAs for the mRNA of cox3 and extensive RNA editing recoding of most genes has occurred. The reasons for this transformation are unknown.
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