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Genetics Corner
a Genetics Column by Lorraine Shelton, BA, BS
If you want to ask a question, click here
Topic: What color can I get?
Question: Can you get a brown patched tabby out of a red classic tabby CPC (with no brown/blue tabby behind him) X a Tortie point himmie? BelindaAnswer: No. As long as you are SURE that there is no true agouti behind the red male. What usually happens is that a tortoiseshell is born that is very hot and the "stripes" you see are the result of the natural "stripiness" of the red patches. If there is little enough black, the effect can be similar to the appearance of a brown patched tabby.
Topic: Hernia
Question: I am considering purchasing a new queen for my breeding program. She is everything I have ever wanted. My one thing I am worried about is that she was born with a hernia and had had to have surgery to have the hernia repaired when she was a kitten. Is this hereditary?Answer: Not all congenital defects are hereditary. Midline defects like hernias can be caused by many things, including: "just a fluke", virus infection in the queen, exposure to chemicals/drugs, etc. It can also be familial. However, my rule of thumb has always been, "Don't breed with anything you don't want to see pop up again sometime". Wish I had a more definitive answer for you!
Topic: Chocolate Carriers
Question: My question centers around chocolate and chocolate carrying Himalayans and Persians. Here is the scenario: You have a male who definitely carries the chocolate gene and a female who defiantly carries the chocolate gene. When mated together they only produce one offspring. I understand that when this sort of mating is done and several offspring are produced, they can or cannot carry the chocolate gene. What if there is only one offspring? Is this single offspring defiantly a chocolate carrier? Thanks in advance for your help. JackieAnswer: The breeding that you describe here, between two cats carrying, but not exhibiting, the chocolate gene, is a popular breeding choice for those working with these challenging colors and one that often has good potential of progressing type on this color series in a rewarding manner. However, it can be a disappointing decision as well. The breeding is done with only one goal in mind: to produce a "visual" chocolate or lilac cat. The odds are not in the breeder's favor, as each kitten born only has a one in four chance of exhibiting the desired color. The larger the size of the litter, the better the chances that the desired color of cat will be produced.
A problem occurs when a kitten of the desired color is *not* produced. Or, even more commonly, the chocolate/lilac kitten in the litter has all the Persian type of a Maine Coon, while a solid black littermate looks destined for success in the show ring. Does the breeder keep this wonderful black kitten? Just as each kitten in this breeding has a 1 part in 4 potential of being a chocolate or lilac, it also has a 3/4 chance of NOT being a chocolate or lilac. Does this automatically make these kittens chocolate/lilac carriers? The disappointing answer is, "Maybe they are, maybe they ain't".
Remember, each kitten receives one copy of each gene from each parent. A chocolate carrier parent has two different "flavors" of this gene to offer the unborn kitten: a dose of chocolate or a dose of non-chocolate. These options sort independently, so the three possibilities are as follows:
1) a dose of chocolate from one parent and a dose of chocolate from the other. This kitten will be chocolate/lilac. Odds are 1 in 4 = 25%
2) a dose of non-chocolate from one parent and a dose of chocolate from the other. This kitten will be carrying chocolate. Odds of a black kitten from a carrier to carrier breeding being a chocolate carrier are 2 in 3 = 67%
3) a dose of non-chocolate from each parent. This kitten will NOT be a chocolate carrier. Odds of a black kitten from this breeding being a non-chocolate carrier are 1 in 3 = 33%
Remember, these are STATISTICAL ODDS, and your mileage may vary! I have done carrier X carrier breedings where three out of four kittens were chocolates! And I have done breedings of a chocolate to a chocolate carrier (where the chances are much more in my favor) where not a single chocolate or lilac kitten was produced. These odds apply whether there are 8 kittens in the litter, or only one! Each individual kitten "rolls the dice" statistically, and the results are independent of what happens with any other kitten in the litter.
So the breeder is faced with the question that has faced every breeder working with chocolate and lilac Persians. at one time or other: " Do I feel lucky?" Since type is completely unrelated to chocolate carrier status, there are no "clues" a breeder can rely on to decide if the kitten is "worth keeping" (or for a buyer, "Is this kitten worth buying?"). If the breeder has a visual chocolate or lilac of the opposite gender to breed to this "maybe" cat, they may choose to keep it. This way, if a chocolate or lilac kitten is produced in the NEXT generation, they have proven that the "maybe" cat is, indeed, a chocolate carrier. If no chocolate or lilac kitten is produced, then, since one parent exhibits this trait, at least every one of the next generation of kittens will DEFINITELY be carriers of this gene.
A strong word of caution: keeping a cattery-full of "maybe" carriers is a dangerously effective way to get into the unhealthy situation of having too many cats. Is it any wonder that top quality chocolates and lilacs are so rare??!!
Topic: Cowlick
Question: I have a gorgeous Persian kitten with a pedigree to die for. Unfortunately, she has a cowlick on her face that presses upon her nose leather and, in turn, leaves half of her nose looking slightly misshapen. I'd certainly feel more comfortable using her in a breeding program if I had some confidence that such occurrences are anomalous and not inherited. This problem has not, to anyone's knowledge, occurred in other breedings on either side of her family tree--at least, not in recent history. My vet suspects this cowlick occurred in utero--possibly as a result of her shoving her paw up against her nose; were it the product of genetics, she says she'd expect the formation to appear on both sides of her nose, given the body's propensity for symmetry. Several of my breeder friends, furthermore, (some of whom have delivered an occasional cowlick-marked kitten themselves) argue that the occurrence represents a developmental accident, not a genetic one, but they can't recall seeing anything written about the subject itself. As you might guess, none of us has a clue about where we might begin to research this problem. Have you any information about it yourself? TammyAnswer: OK, now THIS is one I haven't been asked before! Yes, the type of abnormality that results in a cowlick is most likely a result of environmental factors at the level of the hair follicles, in utero or as a very young kitten, rather than hereditary factors. As you have done, examining if this trait has occurred before is the first step to determining the likelihood that the trait will be passed on in future generations. This is why good record keeping is essential in any breeding program. Tracking down traits like these requires knowledge of the littermates and repeat breedings of cats in the pedigree, not just an examination of only the cats in the pedigree. If this cat throws the trait more frequently in her offspring than would occur in any other Persian population, then there may be evidence for inheritability of this trait. Frankly, it sounds pretty cute to me! ;-)
Topic: Chocolate? or Not?
Question: This is a rather mute point...as I am no longer breeding, but I will always wonder about these kittens. We bred and showed Himalayans for many years. During this time, we used CPC's and Persians. in abundance to improve type. Almost always, black or blue. We also did extensive line breeding. Most of our pointed kittens were very pale in point color...and retained the pretty clear and light coat color..including the seal points, into adulthood and old age. My question pertains to some of our solids. With in a litter..we would have pointeds and solids...blacks, blues and "browns". They were NOT chocolate...they did not have pink noses or paw pads, and the line was well known, and no chocolate appeared in a 6 generation pedigree. It was not due to sun bleaching, or ill health. Some of them did go black eventually, others darkened, but not to a black. They were the color of a sable Burmese or even a Havana brown. What I was wondering, is I know the Himalayan gene is part of the albino series. Could some of these cats have expressed that albino gene even into the solids ? They did not appear pointed as a burmese...just the brown color...gold/copper eyes. I have always been curious...and as I stated, it matters not now, as we have spayed and neutered all our cats and are no longer breeding, but would love some insight into what the cause of the "self seals" would be. I can email "greasy kid " pictures of some of the kittens...and could probably dig up a pedigree if needed. Thanks MaryAnswer: This is a very common phenomenon and I get approached with frequency about this matter, making the point far from moot! As you have stated, these "browns" are not chocolates, although, unfortunately, some have been shown and even championed as such. There are three phenomena that can contribute to a genetically black cat appearing "brown": 1) Rusting. This is oxidation of the pigment in the coat by saliva and/or sunlight. This is a common cause of spoiled color in cats that are born black, but then turn brown. True chocolate cats are born unmistakably the color of a chocolate bar. 2) Heterozygosity at the chocolate locus. In has been my experience as a chocolate and lilac Persian breeder that some, but not all, black chocolate carriers are not a true, jet black, but can be brownish in color. This trait can not, however, be used to definitively identify chocolate carriers. 3) Selective breeding for light expression of pigment. The first Himalayans in England were bred to the finest Persians. in that country. This included the very pale "lavender" blue Persians. renowned of song and story. The same factors that make a cat pale blue in color could also have the effect of making blacks lighter in color, resulting in a brown colored, while genetically black, cat. "Faux chocolates", both pointed and solid, are seen with some regularity in Himalayan lines that are known for throwing very pale blue and cream CPC's. The clue that this is the most likely cause of the phenomenon you have seen in your own cats is that the body color of your Himalayans are light as well. This third factor is the one that I believe was at work in your program. These brown colored CPC's, from your experience, are desirable... as they can be the key to light body color in their pointed offspring
Topic: Is it a tabby or a solid?
Question: A friend and I have bred a red tabby and white male to a brown tabby girl (out of a blue tabby and brown tabby mix). There is a solid blue and blue and white kitten (both male) in the litter. The kittens are now a little over two weeks old. How, and a what age, does one determine whether these kittens are indeed solid, or tabby?? For reference there were also brown tabbies, brown patch tabbies and black and whites in the litter as well.. LindaAnswer: Pink nose leather is the most common distinguishing feature between a solid and a tabby cat. Expression of the agouti ("tabby") gene usually causes a pink to rose colored nose, outlined in darker color, in all base colors. This is usually apparent at a fairly young age. White spotting can interfere with this method, as the presence of a white blaze encompassing the nose will also turn the nose leather pink.
Topic: White Chin
Question: In reading your response to the agouti gene, I had to ask...Isn't it true that a red tabby with a white chin has in fact at least one good agouti gene? I always thought that a red or cream tabby with a white chin will produce brown or blue tabbies, if bred to black or blues of some sort, of course. Correct me if I am wrong please. ( I am not referring to the white spotting genes.) A.Answer: Although your statement is frequently the case, the presence or absence of a white chin can not be used with 100% certainty to differentiate between an agouti ("true") red/cream tabby and an apparent red/cream tabby ("non-agouti"). As cats are selectively bred within a program for strong expression of tabby pattern, the white chin will appear in even the non-agouti red and cream cats. Generalizations can be drawn as familiarity with one's own program increases, increasing the odds of identifying a cat appropriately, but these generalizations should not be assumed across other programs. If you use this to make assumptions about a cat's genotype, you *will* get fooled... sooner or later!
Topic: Papa who?
Question: I have a cream queen who I bred to my red male. I observed this breeding. She has had 4 kittens, 2 red males, a red female and a TORTIE! So my young black kitten (the only other male in my house) must have figured out "the process" and bred her too. Now, I am fairly sure that reds are all sired by my red male... but what do I do about registering the litter? KarenAnswer: I believe that commercial paternity testing through PE-Zoogen is available. You will need blood or cheek swabs from the mother and all potential sires. It isn't cheap, but if you truly want to accurately register a kitten to be kept for breeding, it is the only way to do it. As someone who has spent hundreds of hours chasing down pedigrees all the way to the turn of the century... only to find a white kitten registered out of a black bred to a blue... PLEASE do not use any cat for breeding if you are not 100% of the parentage. To do so is showing great disrespect to the breeders before you that have worked so hard for over a hundred years to create the pedigrees behind today's cats. No "Ifs" or "Maybes" appear on these pedigrees.
Topic: Tail Kink
Question: I have a 4 month-old kitten who is a beautiful show cat, however he has a very small tail kink. In fact, it is so minor that I can't even find it every time I feel for it. What are the chances of his kittens inheriting a tail kink? LoriAnswer: Whether it is a tail kink or some other "tiny, little problem," this is probably the most common question about genetics I get asked, and I know that there is only one answer folks want to hear: "Oh, no, XXXX's not a heritable problem. Breed Away!" I wish I had a better answer than the response I always give: Don't breed with anything you don't want to see later. Whether we know the precise mechanism of defects like this or not, it happened once and it can happen again. Cat observers have known for centuries that tail kinks are familial (they run in families). Because this is commonly solely a cosmetic defect, you may decide that the risk of having a tail kink on a kitten or few is worth the advantages of having this boy in your breeding program. Just remember my words of caution and be prepared for the frustration and disappointment in the next generations when your boy produces the little kitten or grand-kitten that "would be Cat Of The Year if only he didn't have that little tail problem" . And Murphy's Law says he will be!
Topic: Tabby Gene
Question: I am confused about inheritance of the tabby gene. People say that red tabbies are different from brown tabbies. Why? AgnesAnswer: The first thing that Persian breeders need to understand about the world of stripey kitties is that there is no such thing as a solid red (or cream) cat. Once you get past that concept, the rest is easy! In every cat's DNA, the "blueprints" present in every cell of the cat's body, is a piece called the agouti locus. In fact, you and I have a similar gene in our DNA as well. We don't understand everything that this little section does, but in the cat it can influence whether a cat is solid black or a brown tabby. When the agouti gene is in its natural (or "wild type") form, it influences pigment production in cells that work to put color in growing hairs. As each hair grows, black color is deposited in it. The agouti gene's job is to make a protein. This protein builds up in the color producing cells as a hair is growing. When the level of this protein reaches a certain level, it stops the cell's ability to make black color. The cell then switches to the next best thing: it makes orange color instead. The result? A hair that is black at the tip and orange at the root, a brown tabby. When this gene is broken (the "mutated" form of the gene), the process of switching from black to orange never occurs. This results in a solid black cat. Since every gene is inherited in pairs (one from the sire, one from the dam), a solid black (or blue) cat has two "bad" agouti genes, and a brown tabby or blue tabby has two "good" agouti genes or one good one and one bad one (it only takes one copy of the wild type gene to do the work of switching color). Chocolates and lilacs become chocolate tabbies and lilac tabbies in the same manner. So what about the red and cream cats? How can a tortoiseshell (not a tabby) girl bred to a black boy (also not a tabby) create a red TABBY kitten?! Shouldn't that kitten have only "bad" agouti genes? We learned above that the purpose of the agouti gene is to turn off black and switch it to orange. In a cat with no black, however, it takes the dark red and turns it into light red, dark cream into light cream and thus creates stripey cats. But here is the confusing part: in red or cream cats, BOTH "good" *and* "bad" agouti genes will cause this striping to occur! Therefore, you can't look at a red or cream cat and know whether it has bad agouti genes or the good ones. If all he has are "bad" agouti genes, no matter how stripey that red male is, he won't produce brown or blue tabby kittens unless he is bred to a tabby girl. And the converse is true: a red or cream cat can *appear* absolutely solid, sound to the roots, but have good agouti genes underneath. You then breed your prize winning solid red Grand Champion to a black girl and may be shocked to see a litter of brown tabby kittens! YOU CAN NOT TELL BY LOOKING AT A RED OR CREAM CAT WHETHER THEY ARE A "TRUE" TABBY OR NOT. If every red or cream cat is supposed to be stripey, how come we have those beautiful red and cream show cats in the solid division? This illusion of solid color can be produced through selective breeding. If you breed for good striping in your tabbies, regardless of color, you will produce red and cream kittens with distinct stripes, despite their genotype. If you selectively breed for clear solid color in all your breedings, you will get red and cream cats with less striping as well. If you wish to bring the tabby gene into your solid program, choose a cat that is not red or cream to guarantee that those stripes will be passed to the next generation!
Topic: Pinched Nostrils
Question: I am a new breeder and after much research chose what I thought would be a great female to start my breeding program. She is beautiful She has great boning, doming, ear set, big eyes and a perfect bite. She is black and one thing that I could not see in the photo I bought her from, was that she has stenotic nares. One nostril appears normal, but one is almost completely blocked. I have taken her to my vet and then to two different laser surgeons. Both surgeons agree that the nose conformation on the opposite side is quite normal and the passage beyond this blockage looks normal. The male and female that produced this kitten do not have this problem. One said that you would not see this again in her offspring, but the other said that you probably would. I want to breed only if I would be bettering the breed, not worsening it - do you think this is congenital and will be passed on to her offspring? Thanks for your help! SherylAnswer: Stenotic nares is a trait that is inherited in a familial manner.
This means that we don't know the exact mechanism by which it is passed from parents to offspring, but that cats affected with this trait have family members that are more prone to this trait.
Surgery can be performed to help these cats breathe more easily. Some
veterinarians insist that the cat be altered at the same time the nasal reconstructive surgery is done. This is quite a prevalent trait in the Persian breed and steps should be taken to try and reduce its incidence, as it is a trait that adversely affects the health of the animal. Breeders have been able to breed away from this trait, even when using affected animals, but the fastest way to minimize the incidence of ANY unwanted inherited trait is to stop breeding to affected animals.My rule of thumb is simply "Don't breed with anything you don't want to see pop up again down the road!"
Topic: Genetic Nomenclature
Question: Can you give me a list of all the specific trait letters a cat can have. For example a black cat can have BB or Bb. What are the letters for ears and eyes and all the other stuff. EmilyAnswer: n Robinson's Genetics For Cat Breeders, we have continued the work of Roy Robinson and other geneticists of establishing a standardized nomenclature to describe known genetic traits of interest to cat breeders. As we discover more genes, we will assign them other abbreviations/letters. At this time there are hundreds of different abbreviations applicable to the feline genome, although most of them are used to describe genes associated with chemical functions that are "invisible" to the cat breeder. Abbreviations are used for single genes and their alleles. By convention, an upper case letter is used to describe a dominant allele, and a lower case letter to describe a recessive allele. There are also letter assignments for each disease that is inherited as a single gene mutation. Polygenetic traits (controlled by multiple genes), such as ear size and placement, fur texture, eye shape/color, etc. are not assigned these abbreviations, because they are not inherited in a simple manner that involves only one gene.
On occasion I have had folks appear to be confused on the nature of these
gene abbreviations. Keep in mind that every gene in the feline genome is
present in every cat. We usually only label a particular cat with the
"letters" that we are interested in and need to track. When we discuss a
particular breed, we don't list the letters pertaining to traits that are
always the same in their gene pool. So a Burmese cat has the gene for agouti (A/a), but all members of this breed have the recessive allele (non-agouti, a) of this gene, so it is "ignored" when writing down a list of letters
describing a particular Burmese cat. Every cat, no matter what breed it may be, has the gene locus for Manx tailessness, Scottish Fold ears, Siamese albinism, and Rex curly fur in its genome. But only Scottish Folds, for example, have the "flavor" (allele) of that gene that causes the ears to
fold. Every other cat has the recessive, "normal ears" allele of that gene.The genes of most interest to cat breeders in describing the physical
appearance of their cats are:
A/a = agouti/non-agouti (the gene that turns "tabby" on or off)B/b/bl (superscript lower case L) = black/chocolate brown/cinnamon (gene controls eumelanin pigment granule shape)
C/cb/cs/ca/c second letters are superscripted)= full color/Burmese albinism/siamese albinism/blue-eyed full albinism/pink-eyed full albinism (gene controls pigment enzyme tyrosinase)
D/d = non-dilute/dilute (gene controls distribution of pigment granules in
the hair shaft)
I/i = Inhibitor/non-inhibitor (the white undercoat gene)
L/l = Short hair/longhair (gene controls the length of time that hair grows)
Mc/mc = mackerel tabby/classic tabby (this is new nomenclature based on new data regarding the inheritance of tabby pattern).
O/o = Orange/non-orange (this gene is on the X chromosome, sex-linked).
S/s = White spotted/nonwhite spotted (gene controls the population size of pigment cells)
Sp/SP = spotted tabby/non-spotted tabby
Ta/TA = (second letters are superscripted)= ticked tabby/non-ticked tabby
W/w = White/nonwhite (another gene that controls the population size of
pigment cells)
Topic: Head Bump
Question: I just bought a red tabby 16 week male.He has a protuberance (semi-pointed "goose egg") at the front of his skull/ his sister has one too. He is beautiful. The breeder said it is the result of an overtypping of the prominent dome, in other words, they were trying to get an extreme flat face. Are there any health risks? I am in the 7 days period where I am checking him out medically. Please help.Answer: I do not know of any health risks to this form of misshapen skull. However,
experienced breeders assure me that once this undesirable trait becomes
established in a particular line, it can be very difficult to breed away
from. It is considered a cosmetic fault in the show ring. This abnormality
appears from time to time as a result of selective breeding for the unique
structure of the Persian head. As we attempt to control the structure of the
growth plates of the skull, it doesn't always give us the result we most
desire. If this cat is to be used for breeding, make sure you can bring in
sound skull structure to work on eliminating this abnormality in subsequent
generations.Topic: Inbreeding
Question: Do you think inbreeding is a bad thing? LaraAnswer: It is universally acknowledged by all geneticists that inbreeding is a "bad
thing" as far as the health of any animal is concerned. This holds true
across species, although some species can handle higher levels of inbreeding than other species. Inbreeding results in the increased frequency of inherited diseases, suppression of the immune system, poor fertility, and
weaker/smaller individuals. Carefully breeding for good health can help
minimize these effects, but can not totally compensate for them.The vast majority of our breeds are based on some form of inbreeding. A
small subset of cats is recognized as a breed and controlled as an
independent breeding population. The larger the initial population of cats
is, the better the chances of avoiding inbreeding problems down the road.
Breeds that are particularly "extreme" in type frequently find that
maintenance of a phenotype vastly different than that of the "wild type"
domestic cat requires a high level of inbreeding to "set type". In this
manner, the overall health of the population is compromised in order to
create exceptional individuals.The adverse health consequences of inbreeding can be minimized through sound breeding practices. The most important of these is the ability to recognize early signs of inbreeding depression. If you are getting small litters and other signs of poor fertility, Mother Nature may be trying to get your
attention, letting you know that you've pushed things too far. If your
kittens do not thrive and you are constantly battling infectious disease,
your cats may be too inbred.In order to breed the healthiest individuals, breeders should try to avoid
inbreeding to the greatest extent that they can. The term "linebreeding" is
frequently used to describe lesser degrees of inbreeding. There are no black
and white answers as to how closely we can breed cats without causing
significant health problems. There is no magic number for coefficient of
inbreeding that can label one breeding "safe", but another "dangerous". Pay
close attention to the health of your cats! Let THEM tell you if you are
breeding too closely.One historically dangerous trend in the cat fancy is the overuse of a very
few "fashionable cats". When one particularly popular stud cat is used to
sire an extraordinary number of kittens to provide the entire next
generation of breeding cats, a breed with a large gene pool can turn into a
breed with a very small gene pool in a short period of time! Try not to put
all of your breed's eggs in one basket, in order to provide those outcross
lines you will need in the future to ensure the health of your breed.Topic: Small Kittens
Question: Is there any hereditary condition that produces kittens that don't grow?
I seem to get a lot of small kittens. They are very active, but just don't
seem to grow. LarryAnswer: Small kittens are a potential warning sign of many diverse problems.
Inbreeding is one (see above), but undiagnosed parasite infections,
malabsorption syndromes (both hereditary and otherwise), and low level viral
or bacterial infections are others. Complete veterinary workups are essential in determining what is at the core of the problem. Since some causes are very difficult to diagnose, your vet make recommend a "shotgun approach" to changing your cattery management, with regimens of complete "worming", isolation of cats into smaller groups, and diet changes. Try to breed together different cats/bloodlines for a generation to see if that will produce larger kittens for you. If you have not screened your cats for polycystic kidney disease (PKD), do so. You are right in being concerned about this subtle sign that changes may be needed in the management of your cattery.
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