Some examples of the Harlequin may share some physical characteristics with some Jungle Boas, but the gene acts moreso in an 'incomplete dominant' way, more like hypos.
Breeding the Harley to the Pastel should yield babies with outrageous color that will ALL have Harlequin blood. Maybe half or more, and possibly less, will display more Harlequin traits such as aberancies, striping, hypomelanism and ultra-pastel-like ground color.
If you take offspring from that litter that show aberrancies and more, you can more than likely produce more of the same. If you take offspring that are the 'normal' babies from the bunch, and breed them to a true normal/common, you will still potentially produce Harlequins, but probably not in extreme form.
I believe only few F3's and F4's exist, and Tim and Brendan are happily sitting on them.
I know i've seen some extreme examples, F3's and F4's, and they are simply unreal! Outrageous.
Because of this I believe this line to be far superior to many others out there, regarding potential.... it just needs to get out there and the work needs to be done! I'm trying to help some!
Take care, Joe

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Thanks and take care - Joe Rollo
'Tis not the stongest of the species that will eventually survive, nor the most intelligent, but the one most responsive to change' Charles Darwin