Shih Tzu Coat Color Calculator
Tailored Mendelian matrix for Shih Tzu breeders and owners. Predict rare coat variations, recessive carrier percentages, and full-litter outcomes.
Launch Full Shih Tzu Color Matrix
Load our full calculation engine with pre-set DNA genotypes specifically calibrated for Shih Tzu bloodlines and standard color variations.
🎨 Popular & High-Demand Shih Tzu Color Variations
Dedicated Shih Tzu Calculator Suite
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Calculate the exact daily caloric intake and feeding grams for a Shih Tzu based on weight, activity, and life stage.
Shih Tzu Age in Human Years Calculator
Convert your Shih Tzu's age into human years using breed-specific size and life expectancy logarithmic formulas.
Shih Tzu Coat Color Genetics Calculator
Dedicated Mendelian coat color genetics calculator for Shih Tzu breeders. Predicts all coat variations, markings, and carrier states.
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Shih Tzu Breeding Genetics & Coat Color Inheritance Guide
Dedicated genetic and clinical calculation suite for Shih Tzu breeders and pet owners.
Standard veterinary genetics protocols apply to Shih Tzu.
Comprehensive Multi-Locus Allele Matrix for Shih Tzu
Breeding Shih Tzu successfully requires a granular understanding of how chromosomal loci interact epistatically to produce both standard show-conformation and high-demand rare coat varieties:
| Locus & Gene | Key Alleles Present | Inheritance Mode | Visual Impact in Shih Tzu |
|---|---|---|---|
| A Locus (ASIP - Agouti) | ay, at, a |
Dominance: ay > at > a |
ay produces Fawn / Red; at/at produces Tan Points / Tricolor (tan eyebrows, cheeks, chest, and paws); a/a yields Solid Recessive Black. |
| B Locus (TYRP1 - Brown) | B, b (bc, bs, bd) |
Autosomal Recessive (b/b) |
"Testable Chocolate" (Rojo). Turns black pigment into warm chocolate brown. With dilute (d/d), forms Isabella. |
| Cocoa Locus (HPS3) | N, co |
Autosomal Recessive (co/co) |
"French Bulldog Cocoa". Converts black base into deep dark chocolate. With dilute (d/d), forms Lilac. Double chocolate (b/b co/co) yields New Shade. |
| D Locus (MLPH - Dilute) | D, d (d1, d2) |
Autosomal Recessive (d/d) |
Melanophilin dilution. Dilutes Black into Slate Blue; Chocolate into Isabella; Cocoa into Lilac. Nose leather turns slate or lavender. |
| E Locus (MC1R - Extension) | Em, E, e |
Dominance: Em > E > e |
Em produces melanistic facial mask. Recessive e/e creates solid cream/yellow, completely masking all eumelanin patterns (producing Platinum when combined with dilute chocolate). |
| K Locus (CBD103 - Dominant Black) | KB, kbr, ky |
Dominance: KB > kbr > ky |
KB forces solid black/eumelanin, hiding tan points. kbr causes brindle tiger striping. ky/ky is permissive, unlocking full expression of tan points (at/at). |
| M Locus (PMEL - Merle) | M, m |
Autosomal Incomplete Dominant | Produces marbled patches. Double Merle (M/M) is strongly contraindicated due to congenital sensory deafness and microphthalmia. |
| L Locus (FGF5 - Fluffy Hair) | L, l (l1, l2, l4) |
Autosomal Recessive (l/l) |
Long-coat mutation. Heterozygous L/l dogs carry fluffy with standard short coats; homozygous l/l produces full visual Fluffy Shih Tzu. |
Veterinary Health Clearance & DNA Health Panels for Shih Tzu
Ethical breeding mandates that visual trait selection never compromises structural vitality or longevity. All prospective Shih Tzu breeding stock should be screened for breed-specific hereditary genetic mutations:
| Genetic Test / Condition | Causative Gene | Inheritance Pattern | Clinical Consequences & Breeding Protocol |
|---|---|---|---|
| Juvenile Hereditary Cataracts (JHC) | HSF4 mutation | Autosomal Dominant / Recessive | Bilateral early-onset cataract formation leading to complete juvenile blindness before 12 months. Never breed affected stock. |
| Degenerative Myelopathy (DM) | SOD1 mutation | Autosomal Recessive (Risk factor) | Adult-onset progressive spinal cord neurodegeneration similar to human ALS, causing pelvic limb paralysis in senior dogs. |
| Hyperuricosuria (HUU) | SLC2A9 mutation | Autosomal Recessive | Defective hepatic uric acid metabolism resulting in painful urate bladder stones, recurrent urinary tract infections, and urethral obstruction. |
| Canine Multifocal Retinopathy 1 (CMR1) | BEST1 mutation | Autosomal Recessive | Retinal pigment epithelial blister lesions and retinal detachments. Carrier dogs (CMR1/wt) may be bred to clear partners. |
| Chondrodystrophy (CDDY with IVDD risk) | FGF4 retrogene insert (Chr 12) | Autosomal Dominant | Premature intervertebral disc calcification leading to herniation (IVDD), spinal pain, and acute hindlimb paresis. |
| Respiratory BOAS Screening | Brachycephalic Airway Anatomy | Polygenic / Conformational | Screen stenotic nares, elongated soft palate, and everted laryngeal saccules. Only breed dogs evaluated as BOAS Grade 0 or Grade 1. |
Worked Mendelian Breeding Calculation for Shih Tzu
Consider a typical high-demand planned pairing between two health-tested Shih Tzu carriers:
Planned Breeding Cross:
- Sire: Visual Lilac carrying Testable Chocolate:
B/b co/co d/d ky/ky at/at - Dam: Visual Isabella carrying Cocoa:
b/b Co/co d/d ky/ky at/at
Because both parents are homozygous for dilute (d/d), tan point permissive (ky/ky), and tan points (at/at), 100% of offspring will express dilute tan points. The phenotypic variation depends entirely on the segregation of the two distinct chocolate loci:
-
B Locus Segregation (Brown / Testable Chocolate):
Cross:B/b(Sire) ×b/b(Dam).
Probabilities: 50%b/b(Testable Chocolate base), 50%B/b(Black/Cocoa base carrying testable chocolate). -
Cocoa Locus Segregation (French Bulldog Cocoa):
Cross:co/co(Sire) ×Co/co(Dam).
Probabilities: 50%co/co(Cocoa base), 50%Co/co(Non-cocoa carrier). -
Joint Phenotypic Outcome via Independent Assortment:
- New Shade Isabella Tri (
b/b co/co d/d): $0.50 \times 0.50 = \mathbf{25.0\%}$ (Double chocolate dilute; metallic champagne coat with lavender undertones). - Isabella Tri (
b/b Co/co d/d): $0.50 \times 0.50 = \mathbf{25.0\%}$ (Testable chocolate dilute carrying cocoa). - Lilac Tri (
B/b co/co d/d): $0.50 \times 0.50 = \mathbf{25.0\%}$ (Cocoa dilute carrying testable chocolate). - Blue Tri (
B/b Co/co d/d): $0.50 \times 0.50 = \mathbf{25.0\%}$ (Quad carrier: blue base carrying both chocolate mutations).
- New Shade Isabella Tri (
This cross demonstrates the mathematical power of Mendelian genetics: 100% of the litter will express high-tier dilute tri phenotypes, with a 25% yield of the coveted New Shade Isabella variety, and 100% carrying multi-locus chocolate markers.
Kennel Club Breed Standards vs. Rare Color Preservation in Shih Tzu
When breeding Shih Tzu, it is important to understand the regulatory distinction between official kennel club show conformation standards and genetic health:
- Official AKC & FCI Breed Standards: Major kennel clubs recognize traditional historic coat colors for the show ring—such as Fawn, Brindle, and White/Pied in French Bulldogs, or Solid Black, Brown, and Apricot in Poodles. Non-standard colors (such as Blue, Lilac, Isabella, or Merle) are classified as show disqualifications.
- Genetic Viability of Rare Colors: From a biological and veterinary standpoint, coat color dilution alleles (such as
d/dorb/b) do not inherently cause systemic illness when accompanied by rigorous OFA health clearances. The primary exceptions are Color Dilution Alopecia (CDA) in certain blue breeds and Double Merle (M/M) auditory/ocular defects. - Preservation Breeding Ethics: Ethical breeders must always prioritize conformational sound structure, open nares, normal spine radiographs, and clean genetic health panels over purely aesthetic rare coat colors.
📚 Academic References & Literature Citations
- Ruvinsky, A., & Sampson, J. (2012). The Genetics of the Dog (2nd Edition). CABI Publishing. Molecular genetics of coat color loci and phenotypic expression.
- Schmutz, S. M., & Berryere, T. G. (2007). Genes affecting coat colour and pattern in domestic dogs: a review. Animal Genetics, 38(6), 539-549.
- UC Davis Veterinary Genetics Laboratory (VGL). Canine Coat Color Genetics & Allele Frequency Registry.
- American Kennel Club (AKC) & Orthopedic Foundation for Animals (OFA). Canine Health Information Center (CHIC) Breed-Specific Testing Requirements.
Frequently Asked Questions About Shih Tzu Genetics & Coat Colors
In breeds like the French Bulldog, the rarest and most complex varieties include New Shade Isabella (combining homozygous dilute d/d with both testable chocolate b/b and cocoa co/co), Platinum (dilute chocolate masked by homozygous recessive red e/e), and visual Fluffy Isabella Merles (carrying homozygous long hair l/l alongside dominant merle M/m and dilute chocolate).
Yes, absolutely. Because many rare colors are governed by autosomal recessive mutations (such as dilute d, chocolate b, cocoa co, or fluffy l), two standard-colored parents (e.g. Fawn or Brindle) that silently carry these recessive alleles can produce rare color puppies. When two carriers mate, each puppy has a 25% statistical probability of inheriting the visual recessive coat.
Official kennel clubs (such as the AKC and FCI) established their written breed standards based on historic working and companion traits present during breed formation in the late 19th and early 20th centuries. Colors not documented in original foundation stock are classified as non-standard disqualifications to preserve historical breed uniformity, even though many non-standard dogs are 100% purebred and clinically healthy.
Breeding stock should complete the Orthopedic Foundation for Animals (OFA) / CHIC recommendations for the breed. For Shih Tzu, this typically includes: DNA screening for Juvenile Hereditary Cataracts (JHC), Degenerative Myelopathy (DM), and Hyperuricosuria (HUU); OFA evaluations for Patellar Luxation and Cardiac Health; radiographic spinal screening for hemivertebrae; and a veterinary respiratory assessment (BOAS grading).
The "Fluffy" long coat trait is governed by the Fibroblast Growth Factor 5 (FGF5) gene at the L-locus. It is inherited as a simple autosomal recessive trait (l/l). A dog with one copy of the mutation (L/l) displays a standard short coat but carries the gene. To produce visual Fluffy puppies, both parents must contribute at least one copy of the l allele.
Breeding two merle dogs together (M/m × M/m) creates a 25% statistical risk of producing homozygous "Double Merle" (M/M) puppies. Double merles lack pigment-producing melanocytes in the inner ear stria vascularis and eyes, leading to high rates of permanent congenital sensory deafness, micropthalmia (abnormally small or missing eyes), and partial or complete blindness. Ethical breeding guidelines strictly prohibit merle-to-merle matings.