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This page on genetics is a combination of many articles in books, on the net and tons of research
on this subject  that I have gathered throughout  the years and have simply rewritten.

By: Raymond Oppenhiemer, Bull Terrier Breeder
Published in his book: "McGuffin and Co."

1. Don't make use of indiscriminate out crosses. A judicious out cross can be of great value;
an injudicious one can produce an aggregation of every imaginable fault in the breed.

2. Don't linebreed just for the sake of linebreeding. Linebreeding with complementary types can bring
great rewards; with unsuitable ones it will lead to immediate disaster.

3. Don't take advice from people who have always been unsuccessful breeders. If their opinions were
worth having they would have proved it by their successes.

4. Don't believe the popular cliché about the brother or sister of the great champion being
just as good to breed from. For every one that  is, hundreds are not. It depends on the animal concerned.

5. Don't credit your own dogs with virtues they don't possess.
Self deceit is a stepping stone to failure.

6. Don't breed from mediocritizes. THE ABSENCE OF A FAULT DOES NOT IN

7. Don't try to linebreed to two dogs at the same time; you will end by linebreeding to neither.

8. Don't assess the worth of a stud dog by his inferior progeny. All stud dogs sire  rubbish at
times. NOT ALL ARE CAPABLE OF SIRING GREATNESS. What matters is how good their BEST efforts are.

9. Don't allow personal feelings to influence your choice of a stud dog. The right
dog for your bitch is the right dog, whomever owns it.

10. Don't allow admiration of a stud dog to blind you to his faults.
If you do you will soon be the victim of autointoxication.

11. Don't breed together animals which share the same fault.
You are asking for trouble if you do.

12. Don't forget that it is the whole dog that counts. If you forget one
virtue while searching for another you will pay for it.

13. Don't search for the perfect dog as a mate for your bitch. The perfect
dog (or bitch) doesn't exist, never has and never will!

14. Don't be frightened of breeding from animals that have obvious faults so long as they

15. Don't breed together non-complementary types. An ability to recognize type at a glance
is a breeder's greatest gift. Ask the successful breeders to explain this subject-there is no other way of learning.

16. Don't forget the necessity to preserve head quality. It will vanish like a dream if you do.

17. Don't forget that substance plus quality should be one of your aims. Any fool can breed one without the other!

18. Don't forget that a great head plus soundness should be another of your aims. Many people can never breed either!

19. Don't ever try to decry a great dog of any breed A THING OF BEAUTY IS NOT ONLY A JOY FOREVER

20. Don't be satisfied with anything but the best. The second best is never good enough.


When you look at an animals pedigree, it tells you what he ought to be. When you look at an animal performing in the ring or in some other event, it tells you what he seems to be. When you look at his offspring and producing record, it tells you what he is. The Pedigree is the family tree of the animal. But it is not absolute proof that the bearer of the pedigree has the hopes for genetic makeup that his pedigree might promise, for it is impossible to know which of those greats in the pedigree are the ones whose genes actually end up in the final product. Perhaps the two or three weak areas in the pedigree are the ones with the most impact on a particular animal. Because an ancestor is present more than once does not mean you can depend on a particular trait of that ancestor's appearing in later generations. A trait is either present or it is not, depending on its dominance or recessiveness and what was copied from each side of the pedigree. The study of a pedigree is an attempt to make order out of what could be called disorder. It recognizes the genetic fact that every living thing is the sum of all its collective ancestors-for better or for worse.


Prepare a synopsis of the qualities of the individual whose pedigree it is. Acknowledge both strengths and weaknesses. Do the same thing with very close ancestors. The closer the ancestor, the more in-depth information you should try to get. Give more credit to an outstanding sire and dam than to an outstanding great grand sire. Try to determine the heritability of traits with close ancestors. Make lists of pluses and minuses of the individuals. Take a hard look at siblings of the individual to assess how they resemble him or her. Try to get some producing records on the sire line and dams line. Consider the degree of inbreeding, line breeding, and/or close breeding in the pedigree you are studying. Study pedigree of prospective mates with the individual you have in mind. Seek out progeny of other breedings that are similar to the one you would be making in the above step to see how they turned out. If a half-sister of your bitch was bred to the same dog, what were the progeny like? Ask yourself, "Does the pedigree seem balanced and does it feel right?" Sometimes this balance is achieved by putting brothers or sisters into the same slot on both the topside and bottom side of the pedigree. Sometimes it is achieved by complementary proportions of inbreeding and line breeding; by complementary proportions of exotic, elegant type and sound honest animals; and sometimes the ultimate in balance is achieved when the great producers in the breed relate to each other in balanced genetic combinations they return to the progeny through both the sire and the dam. Such pedigree credentials would seem impeccable, but still your common sense will be your most valuable asset in reading a pedigree, just as it is with everything else associated with breeding. When the best individuals in your pedigrees are getting further and further back in them, an infusion of new blood from outstanding gene pools is absolutely necessary. Do not allow a wasting away of your line just to keep "homebreds" in it. Unfortunately, the unlimited number of potential genetic combinations that can result from the bringing together of two pedigrees means you do not know until the mating of the results will be favorable or unfavorable, or a combination of both. That is why profiling pedigrees can be such a valuable tool to you. It assists you in making the important decisions in weeding your genetic garden


In normally developed legs, the bones of the upper leg bone, better known as the femur, and lower leg bone, better known as the tibia, are straight. The thigh muscles are aligned with the bones and run from the hip joints in a straight line over the knee joint, attached to the patella or knee cap, then attached to the tibia crest. The only way that a dog with straight legs and good muscle can have a slipped stifle is from a trauma or injury in which the muscles and tissues holding the knee caps in place are accidentally torn or weakened. Many bad stifles are caused by allowing young dogs too much freedom to jump or play on slippery floors. Such stifles are not inherited. To be inherited the thigh bones must bow outward. There is no way that the taut muscles of the leg can follow the curve of a bone. Instead it pulls to the inside of the legs and the patella's are luxated or slipped to the inside of the legs from their correct position. It is the bowed legs that are inherited and cause subluxation of the patella's rather than the subluxed patella that is inherited. When a dog with straight legs runs, the action of the muscles is free and they pull in a straight line over the center of the knee caps, but when the legs are bowed and the dog runs, the knee caps are pulled to the inside of the legs. In so doing, most of the supporting tissues around the Patella's are weakened and become torn so that the patella's are free to slip in and out anytime there is the least amount of pull


The meaning of these two unfamiliar words that are part of the genetic vocabulary. Everyone today knows the meaning of the words homosexual and heterosexual. Let's define them. A homosexual prefers a member of the same sex, while a heterosexual prefers one of the opposite sex. You know that a zygote is a fertilized cell or the union of two sex cells, the sperm and the ovum, and you know that in this cell lie the 39 pairs of chromosomes and the thousands of genes that contribute to the development and manifestation of specific traits in the living animal, the dog. Now you should understand the meaning of homozygous and heterozygous. Homozygous means two of the same genes or an identical pair. It is what Mendel called Pure and his pure plants bred true for the characteristics that the pair influenced. Heterozygous means two differing genes in a pair or mixed genes, one of each kind, and is hat Mendel called a hybrid. His hybrid plants were impure and did not breed true. The pairs of homozygous genes may be either dominant or recessive, but the heterozygous genes must be one of each, one dominant and one recessive.


These are the other two most important words in a breeder's vocabulary and, unless a breeder recognizes that every animal is in reality two different beings, he cannot breed with any degree of skill. What an animal looks like on the outside, its physical appearance, is its Phenotype. It is the phenomenon of how certain genes came together to create its appearance. What a dog looks like on the inside is its Genotype or the make-up of the genes responsible for all the good and bad qualities that can be seen in its phenotype and many others that remain hidden within. The Genotype is the blueprint of every trait it inherited from its ancestors and can pass along to future generations. We must constantly remind ourselves that how a dog looks or acts or moves may be no guide whatsoever to the qualities it can pass on to its offspring.


The results obtained by this system of breeding can more certainly be predicted than the average breeder realizes. Few indeed are the dog fanciers who do more than mate a bitch to a dog hoping for results that there is no scientific reason to expect. When by good fortune one or two above average offspring do appear, they have nothing behind them upon which to base an expectation that they will pass on their desirable traits. On the other hand, when such superior offspring are produced by line breeding, and an improvement is shown, it is backed up by the most powerful hereditary influence obtainable because of the simplicity and strength of the ancestry. If the Selection of this ancestry has been good, the "pulls" are all in the same direction.


Selection by pedigrees alone, without consideration being given to the physical traits of the mating pair, is the chief danger in this system of breeding. A line bred pedigree is valuable or dangerous in exact proposition as the individuals have been selected. Line breeding does not replace selection but, on the contrary, demands the most discriminating of choices within the line. If the breeder selects by pedigree, and without consideration to physical compensation, undoubtedly dogs with notable faults will result, and thus line breeding will insure failure quicker and more certainly than will any other known system of breeding. No other breeding plan has ever brought about the good results of line breeding, and no other system will ever be so powerful in the production of consistently good animals, and this with the greatest certainty year after year. The principal requirement is not to abandon individual selection. A pedigree is a guarantee of bloodlines, a record of the blood of ancestors within which breeding operations and selection may, with confidence be confined. The word "confined" is used advisedly for, after line breeding has been practiced for a few generations, the end results is the development of what is in effect of pure breed - a breed within a breed, so to speak. When that has occurred, any attempt to introduce "cold" blood is likely to result in the penalties of hybridization. The departure from line breeding is a kind of "crossing" in a small degree, for when the blood of line bred animals becomes intensified they assume all the attributes of a distinct strain, which in truth they are, and they will likely behave as such for a long time.


A large proportion of pre potent sires have been inbred or at least closely line bred. An inbred dog is, of course, enormously more pre potent than one who has outcross breeding. Its half of the ancestry having a great deal of identical blood is almost certain to dominate the offspring when mated to one of the opposite sex having an "open" pedigree. (An "open" pedigree is one in which there does not appear the name of any one dog more than once in perhaps several generations.) Inbreeding is therefore recognized as the most influential of all breeding plans or systems, supplying the simplest of all pedigrees - an advantage when we recognize the laws of inheritance. It is all that line breeding is and more. When using either system it must be again be cautioned that careful Selection must continually be made, both as to physical compensation and vigor and fertility. In conclusion no other method of breeding equals this for intensifying bloodlines, making the best use of exceptional individuals, and in building a strain within a breed.


Although the doubling up and intensifying of characteristics by this method of breeding insures results that are more probable than possible and, if continued long enough, are a certainty, it works the same for one trait as another, both good and bad. If affects all characteristics of the animals involved. That is why, unless a breeder knows a good individual of his breed when he sees one, or possesses the right stock to start with, inbreeding can bring disaster. On the other hand, when the opposite is true, the most strikingly successful results can be obtained.


By the intelligent application of genetic principles we can choose to reinforce traits that we consider desirable and reduce the incidence of those we  feel are detrimental by trying to ensure that our litters are as homozygous as possible for those alleles that produce the desired effect. An animal that has a high percentage of its genes in the homozygous state will pass those features on with a great deal of consistency, and is said to be "pre potent" for those features.


Dominant Traits

1. Do not skip generations
2. Generally affect a large # of progeny
3. Only animals showing the trait carry it
4. There is less danger of continuing undesirable- desirable traits
5. The trait may come from just one parent

Recessive Traits

1. The trait may skip one or more generations
2. Generally affect a small # of progeny
3. Only animals homozygous for the trait exhibit it
4. Heterozygous animals can only be determined by mating, so there
is more danger of continuing undesirable traits
5. The trait, when seen must come from both parents


a. high b. low

a. almond b. round c. bulgy

a. wedge b. dome
a. agnation b. straight c. toes in d. toes out
a. sound b. slipping c. out

a. tiny b. set high c. low d. big

a. coarse b. stands off c. flat d. sparse

a. cobby b. long backed

a. 50%+  b. less than 50%

a. extrovert b. shy

a. good b. mis-mark c. recessive

a. yes b. no c. little

a. 3-5 b. 6-7 c. over 7 d. under 3

a. yes b. no

a. up on toe b. down

a. strong b. shallow c. out at elbows d. cow hock

17. BITE
a. scissors b. undershot c. overshot d. reverse

a. straight b. roach c. swayback

a. good stop b. slight stop c. no stop

20. NOSE
a. short b. long c. medium

a. black b. self-color c. poor d. recessive

a. straight w/layback (head high) b. forward head (looks long)

23. GAIT
a. smooth b. loose c. hackney

24. FEET
a. round b. hare feet c. splayed

25. NECK
a. short b. long

a. yes b. no

a. good b. hereditary defects

a. closed b. open

29. RIBS
a. well b. slab-sided c. barrel chested d. too narrow

Keep_ Show_ Quality_ Brood_Sell _Breedable_ Pet spay/Neuter

Dominant                        Recessive

Long Head                                           Short Head
Large Or Long ears                            Small or Short ears
Low set ears                                         High set ears
Wide ear leather                                  Narrow ear leather
Coarse skull                                         Fine skull
Short foreface                                      Long foreface
Erect ears                                             Drop of tipped ears
Dark eye                                               Light eye
Normal eye                                           Large bulging eyes
Brown eye                                             Blue eye
Wire, short or curly coat                     Smooth long or straight coat
Poor lay back                                       Good lay back
Poorly angulated stifle                        Well angulated stifle
High set tail                                           Low set tail
Heavy bone                                           Light Bone
Deep chest                                              Shallow chest
Straight topline                                     Sway back
Good spring of rib                                Poor spring of rib
Short stifle                                             Long stifle
Light pigment                                        Dark pigment
Normal hearing                                     Deafness
Good eyesight                                        Night blindness
Good eye pigment                                 Wall eyes
Self-color                                               Parti-Color
Black nose                                              Dudley nose
Good mouth                                           Overshot or undershot
Normal palate                                        Cleft palate
Normal lip                                              Hair lip
Straight tail                                            Kinked or bent tail

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