Wednesday, July 27, 2005

The wild "horse" and other knots   posted by Razib @ 7/27/2005 12:58:00 PM

Przewalski's Horse:

Some authorities believe the Przewalski is a direct ancestor of the modern day domesticated horse. Others contend this is not possible as the Przewalski is a different species having sixty-six chromosomes while the domestic horse carries sixty-four. It is possible to cross the Przewalski with the domestic horse, and the resulting hybrid is fertile; however this offspring has sixty-five chromosomes. When crossed again to the domestic horse, the new generation returns to sixty-four chromosomes and little influence of the Przewalski horse is evident.

Related to this, FISH analysis comparing genome organization in the domestic horse (Equus caballus) to that of the Mongolian wild horse (E. przewalskii):

...Previous studies of GTG-banded karyotypes suggested that the chromosomes of both equids were homologous and the difference in chromosome number was due to a Robertsonian event involving two pairs of acrocentric chromosomes in EPR and one pair of metacentric chromosomes in ECA (ECA5). To determine which EPR chromosomes were homologous to ECA5 and to confirm the predicted chromosome homologies based on GTG banding, we constructed a comparative gene map between ECA and EPR by FISH mapping 46 domestic horse-derived BAC clones containing genes previously mapped to ECA chromosomes. The results indicated that all ECA and EPR chromosomes were homologous as predicted by GTG banding, but provide new information in that the EPR acrocentric chromosomes EPR23 and EPR24 were shown to be homologues of the ECA metacentric chromosome ECA5.

Also, Invasive honeysuckle opens door for new hybrid insect species:

The animal family tree may not be filled just with forks, but may also contain knots: hybrid species with two different ancestors rather than one, according to a team of Penn State researchers.

"Hybrid" speciation is pretty common in plants from what I know, but the issues surrounding animals are sketchier....

Related: Breakin' free of biology?