ADDITIVE TRAIT is a trait regulated by a set of gene pairs, the sum of which determines the phenotype; these may be affected by environment (e.g. hip dysplasia); they are quantitative traits (degree of dysplasia or joint laxity, amount of coat, depth of pigment, size of bone, etc.)
AFFECTED is a dog that has a disease or fault itself that is hereditary
AGOUTI (also known as wild color or wolf color and includes sable) this gene ‘family’ controls the changes between black and red/yellow pigment within individual hairs and between the pigment distribution between the back and belly; it can also produce a sable colored hair in breeds (Collie, Shetland Sheepdog) where the predominantly yellow/red coat is sometimes interspersed with black tipped hairs which are the sable hairs; the agouti gene pattern has color banded hairs which are made of separate bands of color ending with either a lighter or a darker end, the location of the hair band varies and may be made from 2 or 3 bands of color; the color of the back and sides of the coat is darker than on the stomach, legs, tail and head, the head often has darker markings; the coat may lighten slightly from birth to the final adult shade (Norwegian Elkhound, Keeshond, Siberian Husky, Schnauzer, Weimaraner); the agouti gene locus also contains the saddle and bi-color patterns as well as recessive black which creates the solid black pattern in certain breeds (Labrador Retriever, German Shepherd Dog)
ALBINO is the lack of all pigment in an individual leaving the coat white and the nose, paw pads, lip and eye rims pink; it is rare in cats and dogs and other than the Mudi only reported to occur in Pekingese and possibly the Chihuahua; the irises are white and the pupils are red
ALLELE is one form of two or more alternative forms of a gene which is at the same place on a chromosome, it is roughly synonymous with the word gene, but can be used to identify a specific one which can occur at a specific location on the gene strand, when there are many forms of one gene the word becomes particularly useful
ALLERGY is the state of altered immune reactivity, resulting in reaction to foreign substances (food, airborne particles, etc.) that would not cause any reaction in a normal individual
ASSORTIVE MATING is the method of breeding based on selection for specific phenotypes; the mating of animals with similar phenotypes tends to produce offspring that resemble the parents and is also known as like-to-like, type-to-type or positive assertive mating, the goal is to reinforce desired traits; the mating of animals with dissimilar phenotypes tends to produce offspring that resemble either or both parents and is also known as unlike-to-unlike or compensatory mating, the goal is to avoid reinforcing undesired traits
AUTOIMMUNE DISEASE is a group of diseases resulting from the immune system mistaking tissues as “other” rather than “self”, including thyroiditis, lupus, myasthenia gravis, and generalized demodectic mange; tendency toward these diseases is often inherited and can be exacerbated by inbreeding
AUTOSOMAL TRAIT is a trait determined by a gene located on an autosome
AUTOSOME is any chromosome except the X and Y sex chromosomes
BACKCROSS is 1) breeding back to a parent or grandparent; 2) breeding a crossbred (dog from two different breed parents) back to a purebred of the same breed as one of the parents
BADGER is a coat color that is a mixture of white, gray, brown and black hairs
BELTON refers to the ticked coat color in English Setters
BI-COLOR (also known as black and tan, brown and tan, etc.) the dog is two colors, one is always tan, the other color can be black, brown, blue or Isabella; white is never part of this pattern; (Doberman Pinscher, Rottweiler, Cocker Spaniel, Gordon Setter); the tan markings are located above each eye, on each cheek, on the lips and lower jaw extending under the throat, two spots on the forechest, below the tail and from the feet to the pasterns and hocks, further extending up the inner sides of the legs; this pattern shows a great deal of variation, even when it is homozygous, the tan points are not always marked and the contrast between the colors is not always distinct, in some breeds (Cocker Spaniel) the areas of tan are so reduced the dog can be incorrectly pedigreed as solid black; white markings can rarely appear on the middle of the chest and feet, these are markings only, not part of the pattern
BILATERAL is when something occurs on both sides of the body
BLACK & TAN (see bi-color)
BLENHEIM is a red and white parti-colored coat in Cavalier King Charles and English Toy Spaniels
BLUE is a coat color associated with the dilution gene, it is also called silver, gray, slate, ash, etc.
BLUE EYED ALBINO (also called cornaz) the coat is white or bluish-gray, the dog has pale blue eyes with reddish pupils and pink nose, eye rim, lip rim and paw pad pigment (Pekingese, Pomeranian, Mudi)
BOTTLENECK is the restriction of a gene pool due to rapid and drastic reduction of population to a few individuals
BRINDLE this gene allows black/brown to show through a yellow/red coat in layers which causes an alternating stripe effect to appear, it is most visible on shorter coated breeds (Boxer, Whippet, Greyhound); other patterns can appear in addition to this pattern such as piebald (Magyar Agar); brindle can appear in a variety of stripe colors including black, blue, brown and Isabella, but it is never mixed with white in the brindled area
BUTTERFLY NOSE is when the nose is only partially pigmented (with black, brown or gray) and spots of pink unpigmented areas remain, usually unsymmetrical
C - D
CANCER is any of a large group of diseases typified by uncontrolled growth of mutated cells; all cancers are genetic in origin (due to mutations), but not all are inherited; many result from mutations in somatic cells
CARRIER is a dog that carries a gene for a trait, but is not affected by the trait, that is, the dog carries the white gene but the dog is black, it also applies to diseases and faults
CATARACT is the dull, whitish, cloudiness of the eye lens or capsule in one or both eyes that may eventually lead to blindness
CELL is the smallest unit of living matter that is capable of self perpetuation
CHINA EYE is an eye with a whitish blue iris, also called wall eye; sometimes it also refers to blue eye/s
CHINCHILLA DILUTION lightens most or all of the red/yellow but with very little or no effect on black/brown, makes a black and tan change to a black and silver; changes yellow to pale cream or near white (Pug, Norwegian Elkhound, Schnauzer)
CHOCOLATE is a brown coat color
CHROMOSOME is a single DNA molecule which consists of hundreds to millions of genes
CLEFT PALATE is the failure of the bony plates of the roof of the mouth to close normally during fetal development, usually leaving a gap or fissure between the palate of the mouth and the nasal passages, it is often accompanied by a cleft lip (harelip)
COI is the Coefficient of Inbreeding (see Inbreeding Coefficient)
COLOBOMA is a failure of a portion of the eye to develop, as in iris coloboma or optic nerve coloboma
CONGENITAL is the descriptive general term given to any trait that is seen at birth or is related to the anatomy at birth, it neither includes nor excludes all hereditary traits or environmental influences or developmental accidents
CORNAZ (see blue eyed albino)
CRYPTIC MERLE is a dog that shows no visible merling on its coat, or it is very difficult to detect
CRYPTORCHIDISM is the retention of one (unilateral) or both (bilateral) testicles in the body cavity, that is, the testicle/s fail to descend into the scrotal sac; also called monorchidism which is when one testicle does not descend
DNA is deoxyribonucleic acid, it is the molecule which encodes genetic information
DAPPLE is another name for the merle pattern; it is used mainly in the Dachshund breed
DARK PIGMENT is eumelanin, the coat pigment that produces black or brown
DEMODEX MANGE is an autoimmune reaction to a mite which normally occurs in the hair follicles of dogs; generalized demodex mange is a chronic condition and is thought to be inherited
DEWLAP is skin that is loose and hangs down from the chin, throat and neck
DILUTION is the effect on a coat color that causes it to become a paler shade like blue or cream
DISTICHIASIS is extra eyelashes that emerge from the glands on the margin of the eyelid (from 1-10 hairs can emerge from a single gland), these protrude inwards to the eyeball and create serious irritation
DOMINANT (DOMINANCE) is a gene that can override the effect of another gene in the pair, it is written as an uppercase letter “A”, “M”, etc.
- COMPLETE DOMINANCE expresses the trait no matter what the other allele is in the pair, for example: B-black/b-red; dogs with one or two B alleles will be black, so B is dominant to b
- PARTIAL DOMINANCE gives partial expression of the trait, depending on the nature of the other allele. Example: M-merle/m-non-merle; Dogs with Mm have merle coloring along with solid patches, those with MM have merle coloring, usually lots of white and possible multiple eye and ear defects
- DOMINANT WITH INCOMPLETE PENETRANCE is an allele which sometimes will not express
DUDLEY NOSE is when the nose never developed pigment but the dog is not an albino (other areas may also be affected)
E - F
ECTROPION is the drooping or sagging of the lower eyelid (also called the haw) that creates excessive drying of the of the cornea and excessive production of tears
ENTROPION is the inward rotation of the eyelid towards the eyeball and is characterized by tearing, blinking, eye infections, pain, inflammation and sensitivity to sunlight
EPILEPSY is any of the various disorders marked by disturbed electrical rhythms of the central nervous system and typically manifested by convulsions
EPISTASIS is 1) the genetic interaction whereby one gene alters or totally masks the phenotypic expression of another gene at a different locus; 2) any type of interaction between genes
EPISTATIC is an allele that is more dominant than another
ENVIRONMENTAL FACTOR is any factor that cannot be attributed to the genes, such as nutrition, climate, living conditions, age, sex, uterine environment
EUMELANIN is the coat pigment that produces black and brown based colors
EXPRESSIVITY is the degree to which the genotype is expressed in the phenotype; an example of variable expressivity would be the difference between the black and tan pattern on two different dogs, one showing a lot of tan and another showing minimal tan markings, or the shape and distribution of white spots on a piebald pattern
EXTREME PIEBALD PATTERN (see white spotting)
FAMILIAL TRAIT is one in which the incidence among relatives of affected individuals is higher than in the general population because of 1) shared genes, 2) shared environment, or 3) a combination of genes and environment
FAWN is the color term for yellow Mudis given by the FCI as the translation for fakó; in other breeds it is the graybrown/ashbrown color and also known as Isabella, lilac and cappuccino
FOUNDER is an individual from whom at least some present day members of a population descend and for whom no ancestral information is available; an ‘effective founder’ is one whose ancestors are only represented through that individual
FOUNDER EFFECT is the change of gene frequency that occurs when a new population is based on only a few individuals who carry only a small fraction of the genetic variation of the parental population; a form of genetic drift caused by a particular founder being more frequently an ancestor of members of the present population than are other founders, resulting in a higher frequency in the population of the alleles carried by that founder
FREQUENCY (of a gene) is the percentage of alleles of a particular type in a population
G - H
GENE, GENES are what carry the information that makes an animal what it is (seen and unseen features) and these are carried in pairs (each animal acquires one set of genes from each parent which then pair together to make each feature); they are the basic unit of heredity
GENE FLOW is the spread of genes from one breeding population to others as a result of migration of individuals
GENE FREQUENCY is 1) the population’s total number of different genes at any given locus; 2) the total of the different genes in a given breeding population at a particular time
GENE POOL is the collection of genes which are in a population of selected animals, that is, the dog has a separate pool of genes from the cat and more specifically, the individual breeds also have genes that are unique to them as well
GENETIC BOTTLENECK (see bottleneck)
GENETIC DRIFT is the random changes of gene frequency produced by chance events, also known as random drift; the tendency of specific alleles to vary in frequency from generation to generation; rare alleles can be lost to a population by this process; effects are more pronounced in smaller populations
GENETIC PREDISPOSITION is a genotype which sets the individual up to develop a disease, however disease will not occur unless the individual experiences an environmental trigger (e.g. autoimmune disease)
GENETIC SCREENING is any of several kinds of tests where DNA is inspected to determine the genotype of an individual
- DIRECT GENE TESTS determine what allele(s) an individual has, they are the most accurate method of screening for hereditary disease
- MARKER TESTS determine the presence or absence of microsatellite alleles known to be linked to a disease gene, presence or absence of the marker indicates probable presence or absence of the gene
- GENETIC FINGERPRINTING uses DNA markers to positively identify an individual
- PARENTAGE VERIFICATION TESTS compare microsatellite markers of an individual to those of its reputed parents to verify relationship
GENETICS is the science of heredity, or simply what happens with the genes that are present
GENOME is the genetic content of a single (haploid) set of chromosomes; all the genetic material that can be found in the chromosomes of a particular species
GENOTYPE is the feature that is in the actual genes that an animal is made from and is not visible to the eye, but may be transmitted to the offspring, that is, a dog may be black to the eye (phenotype) but also carries the white color in its genes so the dog is a black (phenotype) which can also produce white which you cannot see (genotype)
GERMINAL REVERSION is the spontaneous mutation of an allele to the wild type in a germ cell, for example: non-merle offspring of a homozygous merle parent are due to germinal reversion of the dominant merle allele to the recessive non-merle allele
GLAUCOMA is the elevation of pressure within the eye that leads to damage of the optic disk and gradual loss of vision; the age of onset varies, but it typically develops in middle aged and older dogs; the two types of primary glaucoma are open angle and angle closure and are considered hereditary
GRAYING (see progressive graying)
GRIZZLE is a bluish gray or iron gray coat color produced by a mixture of black and white hairs; red grizzle is a mixture of black and red hairs
HARLEQUIN is a pattern that creates ragged black patches on a white background, it eliminates the pigment deficient hairs, leaving only the dark patches; it must appear together with the merle gene and is lethal when homozygous HH or semi-lethal when heterozygous and combined with homozygous MM pattern
HAW is the lower eyelid
HEREDITARY TRAITS are those passed from one generation to individuals in subsequent generations via genes inherited from one or both parents
HERITABILITY (inheritable or opposite uninheritable) is what is able to be passed to the future generations through the genes; also the degree of variation which can be influenced by heredity
HETEROSIS is the pronounced vigor which is characterized by greater fertility, life span, growth and survival, that is typically shown by the offspring of unrelated (genetically dissimilar) parents; it is also called hybrid vigor; it is the opposite of homozygosity ( see inbreeding depression)
HETEROZYGOUS is when two dissimilar alleles are at a locus, one recessive and one dominant, or, two different alleles from any of the possible choices, such as Mm or asaa
HIDDEN MERLE when the merle pattern cannot be seen or is difficult to see on the dog (also known as cryptic merle)
HOMOZYGOUS is when genes are in an identical pair at a locus and can be either dominant or recessive, such as MM or mm
HYBRID VIGOR (also known as heterosis) is the superiority of the heterozygote over the homozygote for a specific trait; or the tendency of a cross between two distinct populations to be more productive or fit than either of the parent strains
HYPOSTATIC is an allele that is less dominant (below) than another; a gene which can have its phenotype altered by action of another gene
I - M
INBREEDING is 1) when two very close relatives are bred together, such as, parent to child or brother to sister; 2) the breeding of individuals that are closely related to each other, although not necessarily directly
INBREEDING COEFFICIENT is the percentage of relatedness in an individual as calculated with Wright’s equation; percentage of inbreeding in a given individual is arrived at by analysis of the common ancestors found on both sides of its pedigree; in the strictest sense it is the probability that an individual will have inherited two copies of exactly the same gene from a common ancestor through each of its parents
INBREEDING DEPRESSION is the reduced vigor and fertility associated with increased relatedness of dogs in a population, or homozygosity; it is the opposite of heterosis
INCOMPLETE DOMINANCE is when the expression of heterozygous alleles (i.e. Aa) produce an intermediate phenotype
INCOMPLETE PENETRANCE (see penetrance)
INSTINCT is a natural pattern that is complete and functional the first time it is invoked, also called a closed behavioral program
IRIS COLOBOMA (see coloboma)
IRISH SPOTTING (see white spotting)
ISABELLA (see fawn)
ISOALLELE is an allele that has no obvious effect
LETHAL GENE is a gene that causes death of the embryo or fetus when homozygous (i.e. HH)
LIGHT PIGMENT is phaeomelanin, the coat pigment that produces red and yellow colors
LILAC is the silvery brownish color also known as cappuccino, Isabella, fawn and other names, it is the characteristic color of a dog that is brown and blue at the same time (bbdd)
LINEBREEDING is 1) breeding together related mates in which the closeness of their relationship to one another is greatly variable; 2) breeding to increase the appearance of one or more particular dogs in a pedigree
LINKAGE is genes and/or microsatellites that are on the same chromosome, especially when positioned close together, linked genes and microsatellites are usually inherited together; the closer the positioning the less likely they will be separated by recombination
LIVER is a shade of brown, usually dark
LOCUS (loci-plural) is the location of an allele on a chromosome
LUXATION, SUBLUXATION is a partial dislocation of a joint; also a displacement of an ocular structure, such as the lens or pupil
MALOCCLUSION is the failure of the upper and lower teeth and jaws to come together forming a proper bite, including overshot, undershot and anterior crossbite (wry)
MARKER is a segment of DNA, often a microsatellite, used for parentage verification purposes or as an indicator of the presence of a gene allele known to be close by on the chromosome
MASK is when a black face mask appears on dogs that are red/yellow in body color (Afghan Hound, Belgian Tervuren, Boxer, German Shepherd Dog, Great Dane, Mastiff, Pug), it can extend as far back as the ears
MERLE (also known as dapple) this gene causes pigment to be reduced in some areas, leaving irregular shapes and spots with more or less intense color, which gives the appearance of darker patches on a lighter background; it affects both black/brown and red/yellow colors but merling is difficult to see on red/yellow based coats; it can appear on any single part of the dog as merely one patch, or in several locations, it can be more or less generalized over the whole dog and called self-merle or limited to the back and head (Collie, Australian Shepherd) when combined with the white spotting gene; the merle gene may also merle the iris of the eye and create in one or both eyes a marbled pattern which can fully cover the iris or only part (neither of which is defective); eye and ear defects can be seen in double merle or homozygous merle dogs and when paired with the white spotting genes; breeding merle to merle should be avoided to prevent these defects as affected puppies do not usually die in utero; homozygous merles are often nearly solid white; this gene also combines with the Tweed and Harlequin genes to produce other patterns
MERLE OCULAR DYSGENESIS is a complex of eye defects found in homozygous merle dogs, including, but not limited to, papillary irregularities, coloboma, staphloma, defects of the lens and of the retina
MICROPHTHALMIA is an abnormally small eye, usually blind, most commonly seen in homozygous merles
MICROSATELLITE/S is a segment of DNA that contains a repeating nucleotide pattern that is highly genetically variable and is used as a marker; highly polymorphic repeating DNA sequences which lie between genes
MODE OF INHERITANCE is the manner in which a trait is genetically passed from one generation to the next (i.e. dominant, recessive, polygenic)
MODIFIERS are polygenes that affect the expression of alleles at an identifiable locus; they are usually designated as plus and minus
MUTAGEN is any physical or chemical agent that causes mutations
MUTATION is any alteration of the genome, chromosome or gene; a change in the genetic code; may be transcription errors, transpositions between chromosomes, loss or gain of chromosomes or portions thereof, or misalignment of DNA sequences caused by radiation, toxic exposure or random error
N - R
OUTCROSSING is when you breed relatively unrelated animals together or the mating of individuals from different lines or distinct sub-populations; in dogs it is applied to breeding of unrelated individuals within the breed; in other species it can refer to the mating of different breeds
PENETRANCE is the proportion or percentage of individuals with a given genotype that exhibit the associated phenotype (i.e. if 100 percent of a population show the expected phenotype, the gene has 100 percent penetrance; if less than 100 percent show the phenotype, the genotype has incomplete penetrance); the frequency with which a dominant allele will express itself when paired with a different allele, for example Bb dogs are always black, so the B allele is fully (or 100%) penetrant, if a quarter of such dogs were red, then the allele would have 75% penetrance
PERSISTENT PUPILLARY MEMBRANE (PPM) is an embryonic sheet of tissue covering the pupil which fails to dissolve in part, it can sometimes attach to the cornea or lens, causing opacities, it is thought to be inherited
PHAEOMELANIN is the coat pigment that produces red and yellow based coat colors
PHENOTYPE is the feature you can see with your eyes or measure with health tests, etc., it is the basic outward appearance of the animal and all effects are taken into account, both genetic and environmental together
PIEBALD (see white spotting)
PIGMENT is the “paint” of melanin that colors the hair or skin; white fur actually contains no pigment at all, there is no ‘paint’ to fill the hair which is actually hollow and thereby creates the white color
POLYGENES are genes that function as a group to collectively control the expression of a trait; the effect of each may be small individually, but as a group they have a more noticeable effect; they are often described to have plus or minus effects on phenotype, that is, they can act as enhancers (intensifiers), reducers (decreasers) or inhibitors (blockers)
POLYGENIC means that a trait is made from the interaction of more than one gene to achieve the feature (additionally environmental or other than genetic factors can have an effect on the final outcome of a trait as in behavior); a trait expressed through the action of multiple genes
POPULATION GENETICS is the study of genetic composition of populations, gene frequencies and factors that alter gene and genotype frequencies through the use of mathematical models to analyze the effects of mutation, selection, migration and drift
PREVALENCE is the frequency with which an inherited condition occurs in a population
PROGRESSIVE GRAYING (also known as graying or silvering) this gene only affects gray color; these pups can be born black and slowly change to lighter and lighter shades of gray as they grow older; the time it takes to complete the process is thought to depend on the genes being homozygous (GG) or heterozygous (Gg), with the homozygous dog reaching full color at about one year of age and the heterozygous dog requiring several years (Pumi, Kerry Blue Terrier, Bedlington Terrier, Bearded Collie, Old English Sheepdog); this gene can be paired with the dilution gene which creates blue, the difference is that puppies are gray starting at birth and continue to get lighter, while the coat of the simple blue dog remains the same blue color from birth or may get darker with time
PROGRESSIVE RETINAL ATROPHY (PRA) is a progressive, degenerative disease of the visual cells of the retina that leads to blindness
PSEUDO-IRISH PATTERN (see white spotting)
RANDOM DRIFT (see genetic drift)
RECESSIVE is a gene that can only be expressed when it is paired with its matching recessive gene (homozygous), in other words it needs its twin to have an effect, it is written as a lower case letter “a”, “m”, etc.
RED is the name of a color, but it can be confusing as it can be the name for brown in some breeds and a red/yellow based color in others
RETINAL DETACHMENT is a blinding eye defect, separation of the retina from the underlying tissue; can be part of CEA or may result from head trauma
RETINAL DYSPLASIA is an abnormality leading to retinal detachment at birth or shortly after birth causing blindness
ROAN (see ticking)
RUBY a rich red color, used in the Cavalier King Charles and English Toy Spaniels breeds
S - T
SADDLE is a dark colored V-shaped saddle covers the back and sides, with the lower point of the V facing the rear of the dog, the rest of the body is tan colored (a black mask may also be present); the saddle is usually darkest at birth and lightens with age; the size of the saddle is variable and may be interspersed with lighter colored hairs (Airedale Terrier, German Shepherd Dog)
SELECTION is the method by which particular matings occur; the differential reproduction that changes a population’s gene frequencies as in:
- Artificial selection which is the differential imposed by human intervention; is practiced by breeders of various kinds of domestic animals, with matings set up to meet criteria of the breeders rather than in response to behavioral cues or survival requirements; reluctant individuals may be forcibly bred, unhealthy or unsound animals given sufficient veterinary support to enable them to breed and offspring removed from incompetent mothers for hand-rearing
- Natural selection is the natural process in which the probability of reproduction is often enhanced by traits that promote survival; is more or less random and results from reproductive behavioral traits natural to each species, as well as the individual’s ability to survive to breeding age, produce viable offspring and raise them until they reach independence
SELF COLORED is a dog that is one solid color or with only a few minimal white marks (see also solid)
SELF MERLE is a dog that is merled over the entire body without any white or tan trim or other markings (only minimal white marks are apparent)
SEX CHROMOSOMES are chromosomes that determine gender of the individual; in mammals, females are XX and males are XY, therefore gender of offspring is determined by the male
SEX LIMITED TRAIT is a trait for which the visible expression is limited to one gender even though the genes may be transmitted by both parents, for example cryptorchidism
SEX LINKED TRAIT is a trait that is produced by the genes on the X and Y chromosomes, the more precise terms are X-linked and Y-linked traits; a trait that is caused by a gene on a sex chromosome, usually the X (the Y contains very few genes, all of them related to specifically male traits) X-linked disorders are passed from mother to son; in the rare instance that a female inherits two copies of such a gene (muscular dystrophy, for example) the effect is usually lethal; no Y-linked disorders have yet been identified, but if they exist they would pass from father to son
SOLID (also known as self colored) the dog is one color only (Labrador Retriever); it may be a lighter shade on the lower portions of the dog, as on the belly, backs of legs and underside of tail (Golden Retriever); there may be a white chest patch or stripe and white on toes, foot/feet, but it never extends up the leg; there is no white on any other part of the body, the chest and feet are the only places white markings can appear on a solid dog
SOMATIC CELLS are all cells except germ cells
SOMATIC MUTATION is a mutation which occurs in a somatic cell; it will affect all cells descending from the mutant cell within the organism, but will not affect offspring; cancer is usually the result of somatic mutation
SUBLUXATION (see luxation)
SUSPECT is a dog that has a chance to carry a trait but it is not able to be proven, such as in the case of parents of a puppy that has gone on to produce a disease, it cannot be known which parent (or possibly both) gave the genes to the puppy, therefore both parents are labeled as suspect (Rover and Flower are the parents of Bobi, Bobi produced a puppy with epilepsy, if Bobi herself is not epileptic, then she is a known carrier, but her parents are both suspect (carriers) as it is not known which one gave the genes to Bobi, and possibly both may have)
TERATOGEN is anything or any substance, agent or process that interferes with normal prenatal development
TEST BREEDING is the mating of an individual to a known producer of a specific trait to discover whether or not the individual also carries the trait
TICKING is smaller sized spots of dark colored hairs on white colored coat areas, may also be affected by another gene which controls the spots to have no flecks of white hair in them and cause the spots to be solid (hence called the flecking gene); the best example of a ticked and flecked dog is the Dalmation; roaning that occurs in some breeds (mainly Setters, Pointers and Hounds) is thought to also be controlled by this gene; ticked breed pups are born white and develop the spots within a few weeks, these spots can be black or brown; ticking coverage ranges from few areas to so many the dog appears to be roaned (a fairly even mixture of white and colored hairs) which is particularly evident in long haired breeds; it particularly occurs in breeds that are primarily white with piebald spots but may also occur on typically solid colored breeds such as the Weimaraner in the form of a chest patch that is ticked which then gradually obscures the white area as the dog ages
TRICHIASIS is when normal eyelashes curve inward and irritate the cornea and cause chronic eye inflammation
TRICOLOR is a coat of three colors, usually black or brown, some shade of red/yellow and white; this pattern is a combination of several patterns; the difference between bi and tri is that white is present on the body (other than simple markings) and there can be varying amounts of it; it can be in a defined pattern (Collie) or a more irregular pattern (Beagle); several genes work in combination to create this outward appearance, it is not the work of a single pair of genes as in the bi-color pattern (tricolor breeds include Collie, Shetland Sheepdog, Australian Shepherd)
TWEED is a pattern characterized on a merle coat which creates a patchwork of lighter spots in the darker areas, each patch has a uniform color and there may be three or more patches, each of a different shade or even color, some being blue, gray or brown on a black based coat, or different shades of browns on a brown based coat; this gene only acts when in the presence of the merle gene, it may be related to the Harlequin gene seen on the Great Dane; breeds include the Australian Shepherd and Mudi
U - Z
UNILATERAL is something occurring on one side of the body only (one eye, one ear, etc.)
WALL EYE is an eye with a whitish blue iris, also called china eye; sometimes also refers to blue eye/s
WHEATEN is fawn, pale yellow or straw color
WHITE SPOTTING (also known as Irish white spotting, piebald, extreme piebald) this gene ‘family’ has several patterns including solid, Irish white spotting, piebald and extreme piebald; this is perhaps one of the most complicated patterns as it is affected by modifying genes (polygenes which have plus and minus factors) which cause the areas of dark and white to be more or less covering the dog and the patterns can appear to overlap each other; in breeds that carry all 4 versions of this gene, specimens can exist from solid dark to all white such as in the Greyhound; when the dog is predominantly white this pattern can be associated with deafness (or when combined with the homozygous merle pattern)
- in the SOLID pattern, the modifiers sometimes allow white markings to appear on the throat, neck, chest, toes, stomach and penile sheath; the most extreme expressions are a solid color dog with no white and the other side of the scale has the greatest amount of white in the pseudo-Irish pattern; Weimaraners, Irish Setters and most other solid colored breeds do not carry the Irish spotting gene and it is therefore genetically impossible for them to have more white than this; it is also called self colored
- in the IRISH WHITE SPOTTING pattern (named for the Irish rats in which it was first described), true spots do not actually occur but rather a characteristic pattern of white trim occurs, the white does not cross over the back, it appears in varying proportions of white on the muzzle, forehead, chest, stomach, feet and tail tip; the extreme versions of the Irish spotting pattern can resemble simple markings on the chest and feet or a minimally marked piebald with a complete collar, white legs, belly and nearly all white face (Collie, Basenji)
- in the PIEBALD pattern, random spots of color appear on a white background; the areas of white are increased to include isolated areas of darker color on a white dog, which are produced by the plus and minus modifying genes to create widely variable areas (Brittany, Papillion, Japanese Chin, many Spaniel and Terrier breeds); extremes can appear from a maximal Irish spotting pattern to a nearly all white dog with several dark spots/patches on the head and body; there is more white than in the Irish spotting pattern with the white often crossing the back
- in the EXTREME PIEBALD pattern, the modifiers continue to decrease the areas of darker color and the extremes range from a near solid white dog with a few spots/patches of color to solid white; the dark patches are usually secluded to the ears, around the eyes and in the rump area; this pattern is usually associated with deafness in one or both ears (Clumber Spaniel, Samoyed, Great Pyrenees, Maltese)
WRY MOUTH (see malocclusion)