Coat Color and Pattern in English Shepherds

Solid Black
Solid black coloring may result from the cross between a black and white English Shepherd and a black and tan English Shepherd. The reason is simple, but requires some basic review of color genetics...

There are several different genes that interact to determine what color and pattern you see in a dog's coat. Three of these genes are involved in producing solid black in a purebred English Shepherd:

K -- Dominant black : dominant allele, causes black pigment to be produced throughout coat
A - Agouti : recessive tanpoint allele causes tan markings on black background (in typical pattern)
S - White spotting : recessive alleles produce non-pigmented (white) areas in coat

Black and tan dogs typically have the following genotype:
kk (two recessive alleles at the K locus -- meaning they produce BOTH black and tan pigment in coat)
a^t a^t (two recessive tanpoint alleles -- meaning black & tan are distributed in a "tanpoint" pattern)
SS or Ss (at least one dominant S allele, meaning there are few/ no unpigmented areas in coat)

Black and white dogs generally have the following genotype:
KK or Kk (at least one dominant K allele, meaning they produce black throughout their coat)
any agouti genes (doesn't matter what they carry here... it will be masked by black pigment)
ss (two recessive alleles for white markings)

The crossing of a black/tan and a black/white means that SOME offspring may inherit the following gene combination -- which will result in a solid black dog:
Kk (presence of dominant black allele means black pigment produced preferentially throughout coat)
Ss (presence of dominant S -- solid color -- allele means few or no unpigmented areas in coat)
Any agouti alleles...doesn't matter -- pattern will be masked by black pigment.