Meisel RP, Delclos PJ, Wexler JR.

BMC Biol. 2019 Dec 5;17(1):100. doi:10.1186/s12915-019-0721-x

The X chromosome of the German cockroach, Blattella germanica, is homologous to a fly X chromosome despite 400 million years divergence.

“We provide two lines of evidence that the X chromosome of the German cockroach, B. germanica, is homologous to Muller element F, which is X-linked in most flies. First, there is a reduced sequencing coverage of nearly half of the Muller element F homologs in male cockroach, consistent with a haploid dose of the X chromosome in males (Fig. 2). Second, there is a decreased heterozygosity of element F homologs in male cockroach, including those with reduced male sequencing coverage (Fig. 3). We therefore hypothesize that element F is an ancient X chromosome that was present in the most recent common ancestor (MRCA) of flies and cockroaches, and it has been conserved as an X chromosome in the German cockroach and many fly species.”