A genetic study of esterase activity in mules, hinnies and their backcross progeny

Abstract

Eight B1 progeny produced by backcrossing fertile female mules and hinmes with donkeys or horses, were assessed for levels of esterase isozyme in their sera. Four bands are found in horses, three fast moving (E3) and one slow (E1), while donkeys show only the slow E1 band. Mules and hinnies, the F1 hybrids of the horse and donkey, show both the E1 and E3 bands. Among the eight tested backcross (B1) progeny, a variety of different combinations are found, depending on whether or not the horse band (E3) has been trasmitted by the mule or hinny parent. The significance of this result is because it shows that irregular patterns of segregation of the horse and donkey chromosomes exist between different F1 hybrids, contrary to some hypotheses proposed previously.