Certain breeds of rabbit (Netherland Dwarf, Holland Lop, Mini Rex, etc) employ the dwarfing gene to get the compact, tiny animal that is described in their breed standards. Without the dwarfing gene, they would still be small, but they would be perhaps a pound heavier than the standard calls for and have slightly longer proportions (longer face, longer ears, longer limbs and body). The dwarfing gene is a dominant gene; if a bunny inherits it, you will see the result. Unfortunately, it is also a homozygous lethal gene. So,without the dwarfing gene, you get slightly oversized false dwarfs. With one copy of the dwarfing gene, you get correctly proportioned true dwarfs. Breed two true dwarfs together, and there's a chance that some of the offspring will inherit the dwarfing gene from both parents; those are what get referred to as peanuts. In addition to being only about 2/3 the size of their viable siblings, peanuts' hind ends are often rather pinched looking, and they may not have control of their hind legs. Though they may be born alive, most peanuts have incomplete digestive systems, so they typically die within 3 days of birth.
