Perry Marshall, Evolution 2.0, page 85
Research at the University of Colorado reports a fascinating discovery about protozoa. This is profound, almost miraculous: Starving male and female protozoans mate (pooling their poverty, apparently), and then completely restructure the genome to make a new nucleus, cutting DNA into 100,000 pieces, then splicing and rearranging the code (650). In other words, a protozoan reprograms its own DNA through a repeating, programmed response to stress—through thousands of simultaneous edits (613). They do this in response to heat shock, pollution, hazardous chemicals, absence of food, and presence of food they’re unable to digest (659). They do this in a few hours!
A cell editing its own DNA is like a writer with 20 Microsoft Word documents open all at the same time, rapidly shuffling pictures, words, and tables back and forth. That’s what’s happening when a protozoan splices its own DNA into 100,000 pieces and rearranges them. Linguistic analysis of the protozoan genome shows that only certain segments get cut and spliced, and apparently only certain arrangements are allowed.* Transposition is not only for bacteria and corn. A recent comparison of primate and human genomes (630) shows that mammals with placentas, including humans, share more than 280,000 transposable elements. Ever-expanding libraries of genome sequences infer that roughly 20 percent of differences between humans, primates, and related mammals vs. marsupials can be traced to massive rearrangements of blocks of data, via Transposition.
650 Prescott, D. M. (2000). “Genome Gymnastics: Unique Modes of DNA Evolution and Processing in Ciliates.” Nature Reviews Genetics, 1, 191–198.
613 Duharcourt, S., Lepère, G., & Meyer, E. (2009). “Developmental Genome Rearrangements in Ciliates: A Natural Genomic Subtraction Mediated by Non- Coding Transcripts.” Trends in Genetics, 25(, 344–350. Retrieved from
659 Shapiro, J. A. (2011). Evolution: A View from the 21st Century. Upper Saddle River, NJ: FT Press.
630 Lindblad-Toh, K., Garber, M., Zuk, O., Lin, M. F., Parker, B. J., Washietl, S., Kheradpour, P., … Kellis, M. (2011). “A High-Resolution Map of Human Evolutionary Constraint Using 29 Mammals.” Nature, 478, 476–482.