1 Comment so far

1. Doctor on September 29, 2009 12:23 PM

   a mule is, it is a cross between a female horse (Mare) and a male donkey (Jack).
   horses have 32 pairs of chromosomes while donkeys have only 31 pairs. When a male donkey and a female horse mate, they produce a mule (a male horse with a female donkey produces a different creature called a hinny).
   Cross between a horse (with 64 chromosomes) to a Prezewalski’s (wild) horse (with 66 chromosomes) produces a hybrid with 65 chromosomes, which is normally fertile. Several domestic horse breeds have 65 chromosomes.
   Mules and hinny’s are infertile. You may have heard that this was because they have an odd number of chromosomes
   The best possible explanation for this is not due to excess chromosomes, but in how they pair up. Chromosomes come in different shapes and sizes, such as metacentric, submacentric, and acrocentric autosomes (non-sex chromosomes); the normal horse has 30 submetacentric and metacentric autosomes, and 32 acrocentric autosomes. The chromosomes in donkeys and horses don’t match in shape (a mule inherits 13 metacentric chromosomes from the mare and 19 from the Jack) this could affect what traits and genes are passed to the offspring, and is possibly the best explanation for their infertility. ..