Genetics Over Simplified
Jelly Bean Genetics 101
(c) Chris Jones
This is going to easy to understand and you won't have any excuse to think differently!
Let's start with the assumption that your stud dog is genetically a big bag of jellybeans.
Your bitch is an equally big bag of jellybeans. In real life each parent would of course
have many, many more possible genetic combinations than those represented by a
colored jellybean. Just as in real life, both the sire and dam have many of the same color
jellybeans (genes) which represent the same breed traits. She and he have different color
beans and different possible combinations in some areas. These represent the individual
and familial characteristics and their variants, including sex-linked traits. (Those
commonly associated with only one sex. This can be a matter of expression only as in an
undecended testicle for example. Obviously the female who may carry a gene for this can
not express it.) Random occurrences may also happen within the breed. These can result
in mutations. Some will be selected as desirable and others will be unsolicited as
undesirable.
If you would like, you can make this a very graphic lesson by actually buying two bags of
jellybeans to try out this over simplified genetic study. Mark one bag “dog” and one bag
“bitch”. Set out 6 small bowls. Without thought as to possible color matches pour a
dozen from each bag into each bowl. Each small bowl represents a possible puppy and
it's possible genetic components. This experiment should give you some idea of possible
random combinations that produce certain traits. You may decide to actually work out
your own hypothetical study on paper using this method if you like.
Let's start with this example, to keep it super simple, red jellybeans are red coat color.
Pink beans represent a dilution gene. When both appear in the same bowl (puppy) those
reds will fade. See which puppies will stay red and which ones will fade by checking
each bowl. Two pink jellybeans mean whatever color the puppy is now, the puppy will
fade to a pastel shade of that color by adulthood. A pink with an orange means only
slight fading. A pink with a white bean means a cream colored pastel will be the final
color. A pink with a purple bean will mean the color will darken with age in all colors.
Keeping to coat color as a possible representation of the jelly beans; Say black beans are
black coat color. Right now there probably aren't very many black beans. Let's say you
decide you would like a black dog. You would choose carefully each time you choose
big bags (sire/dam) to get as many black beans as possible in one certain bowl. Whether
or not you could ever have a black dog would depend on whether or not the big bags
representing the sire and dam have any black jellybeans. If they don't, no matter how
much you want one, you are out of luck. If they have some, you can work at it until you
manipulate the beans until your odds look better. You may be able to carefully pour
black beans into the bowls. This represents selecting the genes for black coat color. You
may not achieve the results you desire in the first batch of pourings, which represent the
first generation. You find that after a while where the concentration of black beans are.
You use these bowls to produce your black dog. After that it is easy to combine the
bowls with predominantly black beans which represent a subsequent generation of
breeding. Then that bowl, or dog, will be dominant for black coat color. In breeding
people often short cut, especially in color breeding. They find a dog dominant for a
particular color and then they know that some of their puppies will probably be that color,
if their bitch carries a recessive gene. (Her “bag” or genetic ability has the capability of
producing the trait even though she herself doesn’t express it.) If the stud dog himself is
dominant for a certain color and if their bitch is carrying any recessives for it, she may
produce it with that dog. (She probably will produce it unless the sample size is too small.
For example she only has one or two puppies and both only inherit recessives for the
color.) We have found that with color breeding in the Shih Tzu, blacks, black and whites,
reds and brindles, parti-colors, solids, patterns, etc. all may be introduced by one
dominant parent into any litter or line which formally did not exhibit that color gene
previously. The recessive genes were there just as color jelly beans but unseen by the
eye, the actual color genes went along generation to generation before they were
combined with a like color code to expose them. This explains color assortment in some
litters and should explain why some colors are hard to produce for some lines. An
example would be the pastel dog/bitch could carry a red gene and surprise a novice
breeder by producing deep red. The brindle littermate bred to a deep red may never
produce red no matter if he is bred to red. (Please keep in mind that coat color and skin
pigment genes are not the same. Some people falsely believe you must have a liver
(pigment) gene to produce red coat color. You can but it is not necessary.) Just as short
but breeding exists in this experiment you can see the effect by adding a bag of black
jellybeans. The odds are up considerably to produce a black puppy. Add a bag of pink
(fading color) red jellybeans and the same thing happens. This is concentration also
called gene frequency. If certain genes are present more commonly in the gene pool then
the traits for these genes will be more frequently expressed. This applies equally to coat
color, temperament, structure or any other genes.
Let's say, that there are other things the breeder wants to produce such as good bites, and
they are represented by lavender beans. Let's say we have found from previous bowl
tests that lavender beans seldom go with black beans. After a while we will have to
either go with the black beans or the lavender. We can look for bowls with more lavender
beans but since rarely does the bowl with black contain a lavender, this will be a harder
accomplishment. We can select for a bowl with as many of these colors or traits as
possible and keep trying until we get a mix that produces everything we like and still
gives us the black and the bite. We may find to get the lavender and black we have to
give up other color jellybeans (representing traits) that we desire. We may decide that
we must go to another dog, who is represented by a bag of jelly beans already loaded the
way we need (with possible combinations for the traits we desire) to achieve the preferred
results. (This would be a stud dog or bitch known for the propensity for producing the
traits desired.) For instance if we already have a nice bite and conformation we desire,
perhaps we would go for the black color to help our fading colors and pigments. If we
need a better bite and one black dog has it and another doesn’t we might consider again.
Even better still try to see as many of the progeny of each dog as possible. Some dogs
consistently produce better results than even their own littermates. This is the term
“genotype” this is what the dog is and what he can produce. (some people use the term
“throw”.) The phenotype is what he is – how he looks and how his gene map worked out
on him. This is not always consistent with what you will get with your bitch. Look to
improve her flaws and faults. He can only do that if he is strong in those areas both
phenotypically (he must at least have those genes for them to be expressed.) and
Genotypically – this can only be told by his progeny. What can he produce with what he
has been given?
Let's get away from coat color and say that a color match in jelly beans (which are
representing actual gene combinations, here) doesn't necessarily guarantee a dominant
gene combination. For example two green jellybeans can mean a short nose but ONLY if
there is also a yellow and orange that go along with the green. If not, your bowl or puppy
will only be recessive for the shorter nose. The similarity of color patterns doesn't
necessarily mean an absolute match. This is because some colors run in sets or patterns.
These will represent your "poly-genetic traits". For starters, to get a longer leg length
you must have red, white and blue in that combination. But if you get two blues in a row,
you can get a deformity of the femur head called Legge Perthes disease which is the
name of the crippling defect, deformed femur heads. So, by carefully watching your
pourings in each bowl, (which represents your monitored, selective matings) you can
select the beans by colors and patterns desired so you will be less likely to double up on
excessive blue beans. In reality, this represents the fact that you have your dogs X rayed
to check femur head conformation. You do this because real life isn't a bag of jellybeans
and you can't see the genes or the femur heads. You must have some way to confirm and
predict the presence vs. absence of this genetic problem.
It has been said that; "Any dog can produce any thing.", meaning any genetic or acquired
trait. That is only true as far as it goes. An unknown (untested) dog is like a random
unopened bag of jellybeans. No one can yet predict what combinations he will produce.
If this dog’s pedigree confirms that he has a completely out-crossed gene pool then the
possibilities are much more open to variety. Let's say the average dog has been bred to
several linebred and out-crossed bitches. Then the breeder would have some idea of what
the dog can do. The breeder may be surprised when suddenly he is confronted with
several problems he had no idea existed. The random combinations were limited by the
number of breedings but as more combinations result (puppies) more traits are expressed.
(This includes undesirable traits as well.) One reason for this is limited sample. For
example in toy breeds the litter sizes are small so the sample size is very limited. In larger
breeds the sample size is larger making it easier to determine patterns and expression of
traits. Now, if this same dog had been tested for certain traits and if his parents and
grandparents had been tested. It might be known that the dog is free from the ability to
produce these undesirable traits. (Say, PRA for example) Let's say too that he and his
parents are X-rayed clear for good femur head conformation. They are now known to
have only sound, solid femur head formation. The breeder can better predict sound femur
heads. It's now quite unlikely that he will be able to pass Legge Perthes disease. On the
other hand if the female line has a history of passing lots of blue jelly beans, sooner or
later, even if the male doesn't throw as many blues, the double blue combination could
possibly still come up. Only if our dog has no excess blues beans because the bowls have
been filled each generation by carefully selecting for non-blue jellybeans – can you be
certain no matches (carriers) can connect. This means you have successfully controlled
this undesirable trait from being expressed by selective breeding the same as you control
the filling of the bowls. The bowls represents manipulation of the genes to only contain
sets with one blue jelly bean, will it make it impossible for the stud dog to produce the
double blue that produces the Legge Perthes problem for example. By carefully selecting
and limiting the possibilities with the jelly beans (genes) this dog can not produce
"anything". He is now limited to the specifically defined and developed trait, in this case;
normal femur head formation. With each successive trait that is selected for, a dog may
become more and more dominant for or against that certain trait. For example, this dog is
confirmed free of PRA. He is free of Legge Perthes, and now we find he is clear (and
several generations behind him are confirmed, to be clear) he has no genes for liver or
bleeding disorders This dog can not produce “anything” with any bitch. He, like his
jellybean bag equivalent, is loaded with the desirable beans and will dilute the other bags
he is combined with. He can be "hot", or loaded for any undesirable trait in this same
fashion. By inadvertently “loading up” on undesirable genes, he can then only express
them. This means he produces them to a much greater degree than would otherwise be
normal. This would be the opposite effect of genetic selection. It would be the result of
indiscriminate breeding or just breeding to make money or as a “hobby” with no
responsibility.
When traits are visible to the naked eye, are easily demonstrated and benign, all is well,
everything is fine. When these traits are more complex and potentially harmful, things
become rather complicated, both genetically and ethically.
An out-crossed dog may inadvertently become dominant for a certain trait or set of traits
by virtue of "random selection". This is why sometimes-good accidents and bad
accidents happen. You hear people say it just depends on the roll of the dice. That is
only true as long as no regulated or controlled selection is going on. Breeders make
selections for coat color, color patterns and/or coat volume all the time for instance. This
is not hard to imagine by virtue of the fact that these are easy to see, define and control.
Many dogs then become strong (dominant) for these traits. How many dogs are
substantiated as dominant for healthy eyes, kidney function, or hip and femur
conformation? How many breeders look for these traits as well as just traits to create a
pretty picture in the conformation ring? Not many, unfortunately. It's a lot more "fun"
breeding for coat and color and "show". Judges don't require an OFA number and many
are not even aware of problems in the breed, like Legge Perthes. Many dog show judges
inadvertently award/reward the most crippled but most cosmetically beautiful specimen
of the breed. In this way dog show breeding can be diametrically opposed to
conscientious breeding.
Don't blame it all on judges, it is not their responsibility or their job to control or even
evaluate breed health issues Unless of course it would make the dog unable to compete
or compromises the integrity of that breed's standard to an obvious degree. By this I
mean Champions can and do have and produce hip dysplasia for example but if these
dogs were unable to walk or stand for examination, they might not become a Champion.
So the degree of the fault and the ability to disguise that fault are what determines the
dog's title, not the Xray or gene pool for that dog. The judge might not have apracticed
eye or even check the rear legs in some cases. This is course perpetuates the deterioration
of the dogs as time goes by and other judges and breeders do the same thing. (Ignoring
real structural faults in order to showcase a glamorous appearance for example.) It is the
breeder’s responsibility to care enough not to allow this to happen and to produce the best
possible representatives of his chosen breed. How many would admit a problem? How
many would do something about it? How many just bury their heads in the sand? How
many sell their problems to someone else? Well, I’ll let you be their judge. . . . .
You can't judge a book by the cover is certainly an apt expression here. Likewise you can
not afford to judge a dog by his title. If your dog is lovely and dripping in coat,
photogenic and about to become a Champion producer, would you think twice about
checking his jelly beans? (I.e., genes, his genetic potential for producing good and/or bad
known traits) If your dog is a "winner" you are "in". No one cares what your jelly beans
look like, do you?
Knowledgeable, ethical, dog breeder's can and do control serious, crippling defects in
their own kennels. It's not that hard to do. It does take a financial commitment and a true
dedication to test and eliminate from breeding dogs that constitute unwise choices. These
are the dogs who by virtue of their health/temperament or structural status compromise
breed integrity. This could mean giving away the bags and/or bowls of jelly beans that
don't make it possible to get the desirable combinations necessary for health and
conformation. It could mean the sealing of bags so no further pouring would be done.
(Equate this to neutering.) This could mean the buying of new foundation jellybean
bags/bowls. It could mean finding a way to select better matches for their jellybean bags.
(Sire/dam) This means, finding dogs certified and/or tested already to help discontinue a
downhill path. By planning, testing, X raying and carefully selecting, the breeder has
tools to identify and define possible eventualities and will not get surprises or at least not
as many of them! After several generations of such selection, the effort is rewarded in
consistence of health and quality. As the desirable genes and gene sequences become
more concentrated, the results will be more predictable and pleasing.
Let's get just a little deeper, say eye stripes require 2 black beans, and 2 blues in sequence
to produce dark black eye stripes on face markings. The fact that that combination is
there for pretty head markings, makes it possible and much more likely, to produce the
double (2) blue if a red, white and blue combination turns up in that bowl or that puppy.
When it does, you get the beautiful dark black eye stripe but also Legge Perthes disease.
We see the risk is then much greater for any dog that carries double blue pairs. This is
an example to give you an idea what happens when we make certain choices. In our
experiment of jellybeans in the bowls, we can SEE and control the results. With the
genes in our dogs, we can only control them to the degree that we KNOW them.
We can't tell what we are producing until we see the actual results. The only way we can
make a reasonably educated guess about certain physical traits is evaluating past
performance and/or screening for or against that respective trait. Since we can't "eyeball"
or measure serious health defects ourselves, we have to rely on clinical evaluation.
Saying we will wait for genetic testing rather than using the clinical means at our disposal
today is like saying, "I'll wait until I have no choices and my gene pool is randomly
mixed, possibly irretrievably damaged before I will find out what I have. That is like
playing Russian roulette. By allowing the spread of seriously harmful genes now and
waiting for genetic testing to tell you what you have, you allow these genes to pervade
your whole breeding program so that there may be no return by the time the genetic
testing does become available. Even if DNA testing is available, it still often takes many
years to be accurate for even one trait in a given breed.
One reason some people choose genetic testing as an alternative to the present day
screening methods, is this allows them time to delay fixing their problems. They defray
testing costs. They secretly hope everyone else will have the same problems or they may
plan to get out of the breed. These are not good reasons to delay responsible breeding
practices now. Responsible breeders realize this includes health and Xray screening. You
can be "in denial" and refuse to admit to having any undesirable jellybeans (genes) in
your kennel but in reality they are not going to go away by themselves. By the time
genetic (DNA and/or gene mapping) testing becomes available, some traits will be
irretrievably lost and others may be permanently fixed in your jelly bean bags (sires and
dams).
I have even noticed a dishonest trend in advertising saying or implying “genetic testing”
on some websites. Let me say that as of 2007 as I write this there is no definitive 100%
accurate genetic testing available of dogs in the USA. Please feel free to correct me if I
am wrong.
If we never test for liver or kidney function, or if we never X ray hips or femurs, how
would we know what we are producing? Producing means putting in the genetic
bank. Once you put something in it's very hard to get out randomly. It takes a special
dedicated and concentrated effort. Naturally, if you have inadvertently put the double
blues in your bowls, you will want to watch them and make sure they don't combine with
the blues from the other parent. How can you do this without looking at what is in the
other bowl? Testing for genetically produced problems is a method of screening out
these problems. You can't see them with your naked eye any more than you can see
genes, so you must rely on an Xray or a blood test to tell you what is in that bowl or dog.
Every choice we make regarding selection of traits, produces a gene or gene sequence
and this produces a physical (or mental) consequence/characteristic. Please if you call
yourself a breeder then take responsibility for your choices!
Do you really love Shih Tzu?
Would you want to come back as one of your dogs or future puppies?
Remember that No Choice is a Choice, too!