Afrotheria genome; overestimation of genome size and distinct chromosome GC content revealed by flow karyotyping

•Genomic features in Afrotheria have been characterised by flow karyotyping.•Reassessment of genome sizes alters overestimations in the genome size database.•Chromosome profiles in aardvark, African elephant, golden mole and manatee are shown.•Small variance in chromosome GC content is observed in the aardvark and elephant.•Aardvark and elephant genomes could be close to an Afrotherian ancestor.

Afrotheria genome size is reported to be over 50% larger than that of human, but we show that this is a gross overestimate. Although genome sequencing in Afrotheria is not complete, extensive homology with human has been revealed by chromosome painting. We provide new data on chromosome size and GC content in four Afrotherian species using flow karyotyping. Genome sizes are 4.13 Gb in aardvark, 4.01 Gb in African elephant, 3.69 Gb in golden mole and 3.31 Gb in manatee, whereas published results show a mean of 5.18 Gb for Afrotheria. Genome GC content shows a negative correlation with size, indicating that this is due to differences in the amount of AT-rich sequences. Low genome GC content and small variance in chromosome GC content are characteristic of aardvark and elephant and may be associated with the high degree of conserved synteny, suggesting that these are features of the Afrotherian ancestral genome.