The S genes - known as
piebald
There are three genes at this locus,
S which is solid or nonspotted.
The sp gene which causes the normal spots on
cockers
and xsp which restricts color
to the extremes, such as only on the head and
around the tail.
The two genes sp and xsp work together always
producing a spotted dog.
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The S genes work like this:
S - non spotted dominant to sp and xsp (does nothing)
sp - recessive to S but dominant to xsp (normal
spotting)
xsp - recessive to S and sp (extreme spotting)
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