What is the "lethal factor" in breeding White chinchillas with other white chinchillas or Velvet with Velvet?

Answer 1

LETHAL FACTOR - This term refers to the inability of certain genes to exist in the homozygous state. The two lethal genes for color involved in chinchillas are White and Velvet (also referred to as TOV - “Touch of Velvet” - or Black, not to be confused with Violet or Ebony). If a homozygous allele of White + White or Velvet + Velvet results from a breeding, the embryo will never develop but be reabsorbed by the mother. It has been said that this may result in a blocked uterine horn.

Answer 2

here is a good site that has that answer.

http://www.silverfallchinchilla.com/