Genetics Over Simplified

Jelly Bean Genetics 101

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!