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Basic Color Genetics Primer...
The following pages are a very basic introduction to shetland colors and patterns. It has been designed with the beginner in mind. Only the more common patterns seen in North America are shown.
   Terms tend to differ by region and personal opinion. I hope you will find this information easy to understand and useful. 

   Commonly discussed genotypes: 
     Note: A locus is just a "location" or site, of certain genes, in this case, a color gene, on the chromosome that controls color.
"A" locus
Aa/Aa
"M" locus
MM or Mm
"B" locus
BB or Bb
"S" locus
SS or Ss
The A locus is where pattern genes are located.
See below for the different patterns.
The B locus is where the base color, either black or brown, is located.
The M locus is where the modified genes are located.
The S locus is where the spotting genes are located.
The beginning two letters are the phenotype, which is the color gene that has been expressed. The phenotype is the color the sheep looks like.
The second set of letters are the genotype, the recessive color gene that may or may not influence the color on the surface.
   A sheep inherits one color gene from each parent, for a total of two at each locus. One gene can be dominant to another gene, making it more likely to express, or the gene may be have incomplete dominance, where both genes express at the same time as they fail to mask each other.
    If the lamb inherits the same color genes from each parent, then the lamb is homozygous for that color. If the lamb inherits two different color genes, one from each parent, then the lamb is heterozygous for that color.  
  
Patterns at the A locus are as follows, listed from dominant to recessive:
Click on each for photos and more info.
Includes pheomelanin and breakthrough base color.
Click here to see shetland colors.
Awt-    White
Ag-   Agouti (fading gene)
Ab-  katmoget
Katmoget and gulmoget are co-dominant to each other.
At-  gulmoget
Aa-  Non-agouti
Other "colors" of interest:
-Iset

-Gulmoget-katmogets