When speaking about chromosomal count, it is but an unusual event to have one species bearing more than once set of chromosomes. But through time and due to the development and diversion and converging of species, there are cases that chromosomal count may go beyond the normal. What's more interesting is that a new study found out about the "existence" of two extinct frog species' chromosomes found to be the structural make-up of one frog species--the African clawed frog!
"The most exciting finding from our study is that we can partition the current X. laevis genome into two distinct sets of chromosomes, each descended from a unique ancestral species. While plant studies have been able to show similar results using related species still in existence, this study is the first time this has been done with two extinct progenitor species," a statement from postdoctoral scholar Dr. Oleg Simakov of the Molecular Genetics Unit of the Okinawa Institute of Science and Technology referring to the discovery of the African clawed frog's chromosomes in ScienceDaily.
Being normally used on laboratory and experiments, the African clawed frog (Xenopus laevis) was found out to be containing almost two sets of chromosomes. The findings were given extra highlight on OIST News upon figuring out that the chromosomes that it beholds came from two extinct frog species believed to be its ancestors.
Based on previous studies on developmental biology, cases of having more than the usual number of chromosomes are already observed in fish and amphibians and even in some plants. This is due to the evolutionary processes claimed to be causing the polyploidy or the increase of chromosome copies through the divergence of species over millions of years.
The chromosomes of the X. laevis were hypothesized to be originating from one frog species millions and millions of years ago, which diverged into two different species and now converged again, creating the African clawed frog. Its relative, the western clawed frog (X. tropicalis), had chromosomes that when doubled, would roughly make up the chromosome count of the X. laevis.
The Okinawa Institute of Science and Technology (OIST) through Prof Daniel Rokshar, Prof. Masanori Taira of the University of Tokyo, and Prof. Richard M. Harland of the University of California, Berkely, spearheaded the study which was published in the journal Nature.