AOAC: COLOR BREEDING IN THE GREAT DANE
Below is a listing with schematics of the outcomes in AOAC (color) breeding in the Great Dane where questions
often arise. Those familiar with "Genetics 101" will recognize these as Punnett
squares. The idea here is to show some simple diagrams for what can be "hidden" under solid coats
like black or blue, as well as to show "what lies beneath" some of the more "dominant" coat
colors in the Harlequin family of Danes. This is by no means intended to sanction the breeding of any particular
color or combination, and deliberately in fact avoids any discussion of the ethics of breeding involved. That discussion
is certainly pertinent to breeders, but is beyond the scope of this article. Please refer to the publications at
breed guardian organizations like the Great Dane Club Of America for information
and guidance as to the multiple issues involved in ethically breeding Great Danes. The below is intended merely
to instruct breeders as to the facts of interaction between phenotype (what a dog looks like) and genotype (what
a dog breeds like). Please refer to the websites of such companies as Health
Gene, VetGen, UCDAVIS
& DDC for information on testing
your dogs for these potential hidden pigments and patterns. For most all of the colors discussed there are now
gene-level tests commercially available. Read also Dr. Schmutz' Genetics
of Coat Color in Dogs regularly for updates.
PLEASE REMEMBER WHEN REVIEWING THESE CHARTS, COMPARING THEM TO YOUR LITTER RESULTS, THESE CHARTS REPRESENT STATISTICAL
AVERAGES, NOT NECESSARILY WHAT IS SEEN IN INDIVIDUAL LITTERS: only over time and with increased numbers are exact
results as shown to be expected--this is called the Law of Large Numbers--and means the "odds" only work
over a long series of rolls of the dice. That does not mean, for example, that getting only one blue puppy in a
litter of eight means the breeder's situation is outside of the facts illustrated below--it will balance out when
the numbers are increased. Color here functions on the same principle as sex in a litter: getting 7 males in a
litter of 8 could easily be "balanced" with getting 6 girls next time, and so getting only one blue when
expecting 4 out of 8 could well, even on rebreeding the same pair, result in a whole litter of blues next time.
In other words, the rules here still apply even when you don't see them in action: mathematicians would tell us
all that there is no law of small numbers.
So while individual results will vary, pooled results will confirm the below is how color genetics do work (i.e
it's not "a crap shoot" as some say, but actually a very predicable set of results if you know what's
what); and so you can use these charts to know what the possibilities are as to color and carrier. Blacks are covered
first: go the the second half of this article (Section B) if interested only in outcomes involving the harlequin
gene. Harlequin breeders do need to bear in mind that even in "color pure" pedigrees every typical member
of the Harlequin family (be it merle, mantle, etc.) can all carry and produce all the variations that are discussed
in the section on blacks. So this first section is also relevant to Harlequin family genetics. Harlequin genetics
are distinctly difficult to manage as they involve so many genes that vary between the heterozygote and the homozygote,
so are quite complex: no color family in all of dogdom is arguably more difficult to understand.
SECTION A. BLACKS & THE RECESSIVES BLACK CAN CARRY:
This first set of diagrams deals with blacks and what colors they can carry sight unseen. These colors include
blue, fawn, brindle and chocolate (they can also include piebald in certain circumstances, but that fact is ignored
in this portion of the discussion for clarity's sake. Piebald or "excessive white" as the geneticist
term it, is covered under the section below that discusses Harlequin genetics & elsewhere.) Any individual
black Dane can carry none, one or more of these recessives, up to all of the four recessives mentioned, and all
four can combine in the offspring in various combinations. For example, a black carrying blue bred to a black carrying
blue and fawn will produce not only black and blue puppies, but black and blue puppies carrying fawn (sight unseen),
and such puppies down the line can produce not only blue and fawn, but also blue fawn. The below diagrams outline
all the possible combinations and outcomes of black, fawn and blue. The same sort of results are possible for also
brindle and brown (called chocolate by many in Danes). But for the sake of brevity & clarity, only the black-blue-fawn
(the most common set of recessives) is shown. But any breeder needing to can simply substitute brown and/or brindle
where blue and fawn are now shown. Of course ALL of these can also be combined, that is not shown, simply as it
involves a very large Punnett square and is a rare enough occurrence in Danes to deal with on an individual basis.
If you only want some "bullets" and avoid a lenghty explanation, click here
for a short "rough draft" of color issues in solid Danes.
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This first chart shows at the top four black Danes all of whom have different genotypes, despite looking exactly
alike. The DDKK Dane is the non-carrier black, the DdKK Dane is the black-carrying-blue, the DDKk Dane is the black-carrying-fawn,
and the DdKk Dane is the black-dual-carrier (carries for both blue and fawn).
The bottom of this first chart shows a blue Dane, a normal fawn Dane and a blue-masked fawn. The blue Dane and
the normal fawn Dane can actually have two genotypes: ddKK is the non-carrier blue, ddKk is the blue-carrying-fawn,
DDkk is the homozygous fawn, Ddkk is the fawn-carrying blue. A blue fawn is ddkk in genotype. Note such a dog could
still carry brown (chocolate) sight unseen.
If non-carrier is bred to non-carrier, all offspring are also non-carriers. If a non-carrier black is bred to a
"simple" carrier (has one recessive, either blue or fawn), all offspring are still black, but 50% are
(statistically) carriers. If a non-carrier black is bred to a "complex" carrier (has two recessives)
then the litter is still all black, however 3 out of 4 puppies will be carriers, one of them for both recessives.
If two black "simple" carriers with the same recessive are bred to each other, then 75% black is expected,
25% of the carrier color (blue, fawn), AND 2 of the 3 blacks will be carriers just as the parents were. When a
simple carrier is bred to a complex carrier, the carrier state of the shared recessive is exposed & carrier
status in the litter is increased over that of the simple carrier parent. If a complex carrier was bred to another
like dog, then both fawns and blues, as well as blue fawns would appear. Look at the diagrams below to visual these
various combinations. |
A NOTE ON THE NOTATIONS USED: for all there are more technically correct ways of identifying various genes, the
old "Little system" so familiar to most breeders is what is used here below, to wit:
K Locus: Dominant K=solid color (black or blue); recessive kk=fawn(brindle) coat.
D Locus: Dominant D=black coat or black mask (stripes); recessive dd=blue coat (mask, stripes)
B Locus: Dominant B=black (chocolate) coat or black mask (stripes); recessive bb=brown coat (mask, stripes)
1. DDKK x DDKK=Non-carrier black to non-carrier black=All non-carrier black offspring:
2. DDKK x DdKK=Non-carrier black to black-carrying-blue=All black offspring, but 50% blue carriers:
3. DDKK x DDKk=Non-carrier black to black-carrying-fawn=All black offspring, but 50% fawn carriers:
4. DDKK x DdKk=Non-carrier black to dual-carrier black=All black litter, but 75% carrier pups, 25% dual carrier
pups:
5. DdKK x DdKK=Black-carrying-blue to black-carrying-blue=50/50 black/blue puppies:
6. DDKk x DDKk=Black-carrying-fawn to black-carrying-fawn=50/50 black/fawn puppies:
7. DdKK x DdKk=Black-carrying-blue to dual-carrier black=75% black (5/6 carriers) & 25% blue (1/2 fawn carriers)--offspring
shown:
8. DDKk x DdKk=Black-carrying-fawn to dual-carrier black=75% black (5/6 carriers) & 25% fawn (1/2 blue carriers)--offspring
shown:
9. DdKk x DdKk=Dual-carrier-black to dual-carrier-black=56.25% black (8/9 carriers), 18.75% blue (2/3 fawn carriers),
18.75% fawn (2/3) blue carriers & 1 puppy in 16 will be a blue-fawn puppy---offspring shown:
SECTION B:. HARLEQUIN FAMILY DANES: SOME BASIC PHENOTYPES & GENOTYPES:
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Harlequin family genetics is a complex situation. The chart to the left shows only some of the broader categories
and very basic phenotypes seen in this family of dogs. Harlequin breeding should not be embarked upon by the beginner
in dogs or Danes, nor the individual who has difficulty understanding the simplified diagrams offered here. Not
only is Harlequin family color difficult to control, and these charts leave out many potentially impacting genes
on color, there are lethals and semi-lethal genes involved here, so breeding harls is nothing to play at. Click
here for another article that discusses variations seen in "show marked"
Harlequin & Mantle Danes, click here for an article that discusses the S locus & the
impact of the piebald gene on basic color, and click here for how the above
colors shown for black danes can also affect harl-family genetics. Click here for a discussion of the genetics
of Mantle.
The dog top left is a Mantle, so necessarily a recessive mm dog. However some Mantles can carry the harl gene,
so for all there is no visual difference, some Mantles are mmHh (harl carriers) and some are non (mmhh)--so there
are actually 6 basic genotypes, if only 5 basic phenotypes. A mantled Merle is shown top right: all normal merles
are the same genotype: Mmhh--they cannot carry the harl gene by definition--if they did they would be Harlequins,
both visually and genetically. A Harlequin is shown next, center left: all normal Harlequins are "dual heterozygotes"
<MmHh> & carry one copy of the merle gene, one copy of the harl gene. To the right of the Harlequin in
the center is a "merlikin": a "double merle" without the harl gene: MMhh. At the bottom is
a "true white" Dane: again a "double merle," but this time a dog with the harl gene: MMHh.
Note that genetic white Danes are not necessarily white, and tradition put whites and merlikins in the same category
as both are "double merles" so can appear similar. Also the S locus recessive (piebald) can make identifiy
correct phenotype difficut when it comes to mostly white Danes. |
A NOTE ON THE NOTATIONS USED: for all there are more technically correct ways of identifying various genes,
the old "Little system" so familiar to most breeders is what is used here below, to wit:
H Locus: Dominant H=Lethal to the embryo in the homozygous state & so noted below (no such puppy will be
born). Heterozygous harlequin carriers will appear a Harlequin if the merle gene is present, otherwise the harl
gene is carried sight unseen and so typically appear black/mantle. Recessive hh genotype is the non-harl-carrier--can
also be black/mantle, but all merles are also hh genotype. Note that any dog not carrying the merle gene can carry
the harl gene without expressing it (because harl cannot express unless in the presence of merle). Mantles carrying
the harl gene (mmHh) are noted as "MANTLE1" & Mantles that are harl gene free (mmhh) are
noted as "MANTLE0" below.
M Locus: Dominant M=Homozygous dog will appear as a "white" or merlikin" Dane and all such "double
merles" are at high-risk for having sensory defects (i.e. they are nearly all going to be hearing and/or sight
impaired in some way). Traditional ethics in animal husbandry required that such animals were humanely euthanized
at birth because of this, and for all that's now an area of controversy & contrasting opinion, because of their
management issues "MM=white merles" are noted below as "semi-lethals" by a gray contrasting
background color. The heterozygous merle-bearing dog will be a normal merle if it lacks the harl gene (Mmhh) &
a normal Harlequin if it has the harl gene (MmHh). The recessive non-merle-bearin <mm> dog is the non-merle
carrier and will appear typically as a black or Mantle, but can be any Dane color other than merle, harl, white
or merlikin.
HETEROZYGOTIC ADVANTAGE: At least a short
comment must be made about the potential for heterozygotic advantage (also called heterozygotic superiority) when
discussing genes like harl and merle. The notion here is the the heterozygote, the hybrid (with two dissemilar
genes) has an evolutionary advantage over either homozygote. So here a merle or a harlequin would, in theory, hold
some selection advantage over the <mm/hh> black/mantle dog just as it obviously does over the lethals and
semi-lethals that occur when the dog is <MM/HH> in genotype. This theory is offered when, as in the case
with the merle and harl genes, you have an ancient gene that obviously confers dissadvantage but still manages
to survive. The sickle cell allele is such a gene: if a child inherits two copies s/he will have Sickle Cell Anemia,
but if the child inherits no copy at all, they will be susceptible to malaria. So the individuals with one copy
of the sickle cell anemia gene and one normal (non-sickle cell) gene has the advantage in certain environments,
so the gene remains in the population, despite the fact 1/4 of the children here will fall ill, because 1/2 of
them from the same parents will then survive malaria. The same argument is put forward for various other human
diseases, and there is also a recognition by ecologists and geneticists of general heterozygotic advantage, sometimes
called "hybrid vigor." There has been no work done on the potential heterozygotic advantage to merle
or harl, so any usefulness is mere speculation, and it may be nothing more than human preference for "exotic"
color that has perpetuated such genes. However merle is known to be a very ancient gene and the Harlequin phenotype
is documented back to classical Greece and even ancient Egypt, so these patterns may have at one time had some
value _as_ patterns, and/or there may be unknown value to such genes, given they both do have effects on the individual
beyond color.
S Locus: Dominant S=SS homozygote will be a solid dog, Ss heterozygote will show some white markings; recessive
ss=piebald or "excessive white" dog. Note that the normal "irish" pattern preferred in the
Great Dane breed can be produced at time by an Ss heterozygote, but this dog then will not breed true. There are
"irish true breeding" (homozygous) Mantle and Harlequins that can consistently produce the Mantle pattern.
But this "true irish" gene is NOT found at the S locus. This S locus recessive (the piebald gene) is
ignored in the Punnett squares below. When it occurs, confusion can result, because it produces puppies with "extra"
white markings. It can therefore be hard to sort genetic merles, merlikins, harlequins, whites from various forms
of piebald. Note that merlikins and whites cannot occur when a Mantle is one of the breeding pair, so any mostly
white animals born to such a breeding are likely some form of piebald. To read more on
piebald, click here. To read about Mantle Genetics, click here.
PUNNETT SQUARES below show the outcome of various breedings using all the typical members found in the Harlequin
family. The convention used below is that all the animals are SS dominant homozygotes and also "true irish"
Mantles. In other words, the issue of piebald is ignored, but as already noted can result in confusion because
this is a recessive gene for "excessive white" that can both mimic the Mantle pattern, and as a homozygote
produces an over-white animal regardless of the dog's other genes. The results below will not vary if pigment color
changes from traditional black to blue, fawn, brindle or chocolate. It might however be more difficult for many
to identify the proper phenotype for the puppies when black pigment isn't present (which is likely why genes like
merle and harl are traditionally restricted to black pigmented dogs). If you want to just see the expected outcome
percentages for puppies by color, see the 2000 O'Sullivan article.
1. HARL X HARL=MmHh x MmHh:
2. HARL X MANTLE1=MmHh x mmHh:
3. HARL X MANTLE0=MmHh x mmhh:
4. HARL X MERLE=MmHh x Mmhh:
5. HARL X MERLIKIN=MmHh x MMhh:
6. HARL X WHITE=MmHh x MMHh:
7. MANTLE1 X WHITE=mmHh x MMHh:
8. MANTLE0 X WHITE=mmhh x MMHh:
9. MANTLE1 X MERLE=mmHh x Mmhh:
10. MANTLE0 X MERLE=mmhh x Mmhh:
11. MANTLE1 X MERLIKIN=mmHh x MMhh:
12. MANTLE0 X MERLIKIN=mmhh x MMhh:
This message prepared by JP YOUSHA (2009) for educational purposes. Written permission can be obtained to disseminate
this message for that purpose & that purpose only. All copyrights & author's rights are to be respected.
For further information contact: jpy@chromadane.com
