Poodle Color Genetics
To understand coat color genetics, you must first understand how basic inheritance works. Some terms you will need to learn are:
Locus - the specific area of a chromosome where a gene or gene marker is located. Plural is loci. Each locus is given a letter to describe it such as the B locus (which contains the B and b alleles) or A locus (which contains the Ay, aw, at, and a alleles).
Gene - what carries the information that determines certain traits.
Allele - each gene has two alleles. The dog receives one from one parent and one from the other.
Homozygous - If a gene has two identical alleles, it is considered homozygous (for example, BB or ee).
Heterozygous - if a gene has two different alleles, it is considered heterozygous (for example Bb or Ee).
Genotype - what genes the dog has. It has nothing to do with their outward appearance.
Phenotype - what the dog looks like. It may not be the same as what genes they have.
Dominant - an allele that takes over another allele and will express the trait no matter what the other allele is. It is always written down as a capital letter (for example, E or B).
Recessive - an allele that will only affect the phenotype if it is homozygous. Recessive genes are always written with a lower case letter (for example, e or b).
Incompletely dominant - an allele that has an effect on the traits shown when there is either one copy or two. Often having only one copy will have a lesser effect and having two copies will have a stronger effect.
Untestable - a gene which has not been mapped yet and can't show up on a DNA test.
Punnet Square - a tool used to determine the chance of inheritance of certain traits from both parents.
* - unknown. Used when writing out gene combinations that are unknown, for example E* when it is unknown if a dog is EE or Ee. Usually only used with a dominant gene, as if the dog had two recessive genes there would be a visible effect.
E Locus - Recessive Red
This is the first locus to look at when determining a dog's color because it can mask all other colors and patterns except for parti. If a dog is ee, it removes the eumelanin in the coat which can hide other traits like merle and phantom. The shade of the dog will be determined by the I - locus and can be anywhere from deep red to white. There are three possible alleles: Em, E, and e.
Em - melanistic mask. Dog may have a darker mask (if kyky at the K locus).
E - normal (non-red). Will only allow red-based colors to show if kyky at K locus.
e - recessive red. Allows the dog to be red, apricot, cream, or white.
Em* - the mask gene is dominant to all the others and may cause a mask on a dog with an A - locus pattern. The degree of masking and whether it is there at all depends on other untestable genes.
EE - the dog is black (if no other modifiers) and cannot produce red / apricot / cream / white puppies.
Ee - the dog is black (if no other modifiers) and carries the recessive red gene. They have a chance to produce red / apricot / cream / white puppies when bred with a dog that is Ee or ee.
ee - the dog is red, apricot, cream, or white. What shade depends on the I - locus and other untestable genes.
K Locus - Dominant Black
The second most important locus to look at is the K locus. This is known as the dominant black locus but it is a bit of a misnomer as the dog will not necessarily be black based on this locus alone. This locus can deny or allow the expression of whatever is on the A locus. There are three possible alleles:
Kb - dominant black. Does not allow the A locus to show.
Kbr - brindle. This gene is untestable, and dogs with Kbr will often test as Kbky.
ky - allows the A locus to show.
KbKb - dominant black. The dog will be black unless other modifiers are present. Whatever patterning is on the A locus will not show.
KbKbr - dominant black carrying brindle. If bred to a dog carrying brindle or ky, it could produce brindle or brindlepoint puppies. This gene will usually test as Kbky even though the dog does not carry ky.
Kbky - dominant black carrying the gene that allows the A locus to show.
KbrKbr - depending on what is on the dog's A locus, the dog will be brindle (if Ay*) or brindlepoint (atat or ata).
Kbrky - depending on what is on the dog's A locus, the dog will be brindle (if Ay*) or brindlepoint (atat or ata).
A Locus - Patterns
The A locus will determine if a dog is patterned, however the dog MUST be kyky for these patterns to show through. If the dog is Kbrky or KbrKbr, the patterns will show but will be brindled. There are four possible alleles:
Ay - sable
aw - agouti
at - phantom (tan points)
a - recessive black (keep in mind while the gene is called recessive black, it is actually more correct that it will just not show a pattern. The dog may still be brown or parti, etc).
AyAy - the dog will be sable and will only produce sable puppies when bred to a dog that is kyky. If the dog is Kbrky or KbrKbr instead, it will be brindle.
Ayaw - the dog will be sable and is carrying agouti. If the dog is Kbrky or KbrKbr instead, it will be brindle.
Ayat - the dog will be sable and is carrying phantom. If the dog is Kbrky or KbrKbr instead, it will be brindle.
Aya - the dog will be sable and is carrying recessive black. If the dog is Kbrky or KbrKbr instead, it will be brindle.
awaw - the dog will be agouti
awat - the dog will be agouti and will carry the gene for phantom.
awa - the dog will be agouti and will carry the gene for recessive black.
atat - the dog will be phantom. If the dog is Kbrky or KbrKbr instead, it will be brindlepoint.
ata - the dog will be phantom and is carrying the gene for recessive black. If the dog is Kbrky or KbrKbr instead, it will be brindlepoint.
aa - the dog will not show any pattern but if it is kyky it will produce patterned dogs if bred to a carrier or patterned dog.
B Locus - Brown
This locus determines whether or not the dog will be brown. Keep in mind that there are several genes for brown so depending on what lab you use, a dog that is visually brown may come back Bb. If a dog is visually brown, count it as bb. There are two possible alleles:
B - black
b - brown
BB - the dog will be black and will not be capable of producing brown offspring
Bb - the dog will be black and will be able to produce brown when bred with another Bb or bb
bb - the dog will be brown
S Locus - White Spotting
This locus determines if a dog will have white spotting, known in poodles as parti. There are two known alleles:
S - no white
sp - white spotting (parti)
SS - no white spotting. The dog is not parti and will not be able to produce parti puppies*.
Ssp - not parti, but sometimes can have a bit of white on the chest, muzzle, toes, or tail tip.
spsp - parti. The dog will be at least 50% white.
*There are other genes that will add white markings to a dog, and most are untestable. These genes are generally known as irish white spotting or whitehead. It is possible for a dog that appears parti to test as SS.
This locus has not been identified yet so it has not been given a letter. For the purposes of this explanation we will be calling it G. There are two known alleles and the gene is incompletely dominant, meaning that only one copy will affect the dog and two copies will affect it more strongly. Puppies are born black or brown and with one copy they will fade slowly over 1-5 years and with two copies the fading will be apparent at 4-6 weeks and take a few years to fully clear.
G - no progressive greying
g - progressive greying
GG - no progressive greying.
Gg - one copy of progressive greying. A black dog will become blue and a brown dog will become cafe au lait. ee dogs and sable / agouti dogs will be unaffected.
gg - two copies of progressive greying. A black dog will become silver and a brown dog will become silver beige. ee dogs and sable / agouti dogs will be unaffected.
M Locus - Merle
Merle is not a color, but it is a pattern that can appear on black or brown based dogs. Merle can vary in its expression, sometimes only showing very little effect, sometimes a lot. Merle can cause a dog to have solid or partially blue eyes. Merle cannot visibly show up in dogs that are ee (red-based) and often fades out of fully patterned dogs (sable, brindle, etc). The only evidence of merle in a red-based dog would be if the dog has blue eyes or through a genetic test. Merle is an incompletely dominant gene so it cannot be carried. One parent must be merle for a merle puppy to be born. When a dog has two copies of the merle allele (MM) the dog will have white patches and can have a chance of visual and/or auditory defects. For this reason, two merles should not be bred together. There are two alleles on this locus:
M - merle. Dominant gene.
m - non-merle
MM - double merle. The dog will be merle and will have white patches and possibly visual or auditory defects.
Mm - merle. The dog will be merle and will carry the gene for non-merle.
mm - non-merle.
Merle is a complicated gene, and while the incompletely dominant factor of merle is generally easily understood, there is the more complicated matter of the length of the merle allele which is expressed as a number. With some very short merle lengths, a dog that has a merle gene will not show any visible merle markings on its body. This is known as cryptic merle. Care should always be taken when breeding merle as it is impossible to tell if a dog is non-merle by looking at them. We highly recommend you join the Facebook group Merle - SINE Insertion from Mc to Mh - The Incredible Story of Merle if you are interested in learning more about the merle gene.