Patterns of genome size diversity in bats (order Chiroptera).

Despite being a group of particular interest in considering relationships between genome size and metabolic parameters, bats have not been well studied from this perspective. This study presents new estimates for 121 "microbat" species from 12 families and complements a previous study on members of the family Pteropodidae ("megabats"). The results confirm that diversity in genome size in bats is very limited even compared with other mammals, varying approximately 2-fold from 1.63 pg in Lophostoma carrikeri to 3.17 pg in Rhinopoma hardwickii and averaging only 2.35 pg ± 0.02 SE (versus 3.5 pg overall for mammals). However, contrary to some other vertebrate groups, and perhaps owing to the narrow range observed, genome size correlations were not apparent with any chromosomal, physiological, flight-related, developmental, or ecological characteristics within the order Chiroptera. Genome size is positively correlated with measures of body size in bats, though the strength of the relationships differs between pteropodids ("megabats") and nonpteropodids ("microbats").

The genome sizes of megabats (Chiroptera: Pteropodidae) are remarkably constrained.

It has long been recognized that bats and birds contain less DNA in their genomes than their non-flying relatives. It has been suggested that this relates to the high metabolic demands of powered flight, a notion that is supported by the fact that pterosaurs also appear to have exhibited small genomes. Given the long-standing interest in this question, it is surprising that almost no data have been presented regarding genome size diversity among megabats (family Pteropodidae). The present study provides genome size estimates for 43 species of megabats in an effort to fill this gap and to test the hypothesis that all bats, and not just microbats, possess small genomes. Intriguingly, megabats appear to be even more constrained in terms of genome size than the members of other bat families.

Analysis of spontaneous gene conversion tracts within and between mammalian chromosomes.

In the present study, we report the first characterization of gene conversion tract length, continuity and fidelity for pathways of gene targeting, ectopic and intrachromosomal homologous recombination using the same locus and mammalian somatic cell type. In this isogenic cell system, the vast majority of recombinants (>97%) are generated by homologous recombination and display a high degree of fidelity in the gene conversion process. Individual gene conversion tracts are highly likely to involve single, independent recombination events and proceed through a heteroduplex DNA intermediate. In all recombination pathways, gene conversion tracts are long, extending up to approximately 2 kb. Most gene conversion tracts are continuous in favor of donor region sequences, but in a small fraction of recombinants (15%), discontinuous gene conversion tracts are observed. In most cases, the recombination donor sequence is unaltered, although in two cases of intrachromosomal recombination, both recombination donor and recipient sequences bear gene conversion tracts. Overall, gene conversion events are similar, both qualitatively and quantitatively, for homologous recombination within and between mammalian chromosomes.