Rp is autosomal dominant but when heterozygous (Rp/rp+) it may give incomplete penetration (in some cases).
Rumpless races misses 2 or more vertebrae, it's not recommended to breed rumpless X rumpless because it greatly reduced fertility !
Exist also a recessive rumpless (rp-2) but not in the hobby-breeding.
The Phoenix not have the Non-moulting (mt) but with the Longtail gene heterozygous (Gt/gt+ Mt+/Mt+) it already show the long tail.