Ben

There was a theory that a homozygous roan (RR) could be a lethal gene. This idea of "Lethal Roan Syndrome" was based primarily on a 1979 study.[2] This study examined the percentages of roan foals thrown by roan parents, and found fewer than expected. The study did not include direct genetic analysis, as such technology was not available at the time. Not finding large numbers of dead foals, the researchers concluded that any homozygous roan fetus was absorbed, thus preventing birth. This study and its conclusions popularized the idea of Lethal Roan Syndrome. This was consistent with the "dominant white" and "lethal white" studies available at the time; later study has shown that the dominant white or "W" gene in horses is lethal when homozygous (see White (horse), and there is a different, unrelated recessive condition called lethal white syndrome. Nonetheless, in the late 1970s, genetic science had not yet developed to provide a clear answer to the roan question.A more recent genetic study of roans by Dr. Ann Bowling refuted the lethal roan theory. Using modern genetic analysis techniques, Dr. Bowling found several homozygous roans and no evidence of a Lethal Roan Syndrome.