The model organism Tetrahymena thermopile carries two nuclei with distinct genomes: an unrearranged germline genome with five chromosomes, and a somatic genome reduced in size by a third and with 181 chromosomes.
The machinery that carries out programmed DNA rearrangements is composed of domesticated transposases. One is catalytically active, five play architectural function essential for the accuracy of the process.
Computer simulations reveal the potential and limitations of recently proposed CRISPR-based cell lineage recorders, and suggest how the recorders' design can be optimised to yield more accurate cell lineage trees.
Independent dating techniques have established that the H. naledi fossils are between 236 and 335 thousand years old, indicating that small-brained hominins with relatively primitive body shapes co-existed with our early ancestors in Africa.