Ash
Phenotype
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Genotype
​aa + Dominant gene
Black + dominant chestnut gene
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Breeding Info
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Reference Photos:
Chocolate Agouti/Sienna
Phenotype
​"The base color is a rich red-brown. Undercoat grey-brown. Cover hairs chocolate brown. Belly fur light silver gray. Eyes black."
- LSK Standard for Sienna
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Genotype
​A- bb
Agouti + chocolate
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Breeding Info
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Reference Photos:
Comparison photo showing cinnamon, agouti and chocolate agouti
Harley
Phenotype
​Long fur.
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Genotype
ll
Two copies of long hair (harley)
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Breeding Info
​Very commonly associated with skin issues, and is largely considered unethical to breed in the UK. Velveteen may reduce the incidence of skin issues.
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Reference Photos:
Hairless
Phenotype
Varying levels of hairlessness depending on the gene at play.​
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Genotype
Charles River - fcrfcr - virtually hairless. Homozygous embryos are less viable and are often reabsorbed.
Fuzzy - frhfrh - have minimal hair in adolescence, then lose this fur. Kidney issues and failure are common.
Fuzzy and Charles River - fcrfrh - more viable than homozygous Charles River hairless.
​Nude - rnurnu - whiskers and short hairs on head present. Slower growth rat. Does not have a functioning thymus, leading to immunodeficiency.
Shorn - shnshn - sparse hair. Smaller size and abnormal hearts and kidneys.
Vibrissaeless - vbvb - lack of hair and whiskers. Prone to skin issues and unable to lactate.
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Breeding Info
Prone to scratch injuries as they don't have fur to protect them. Commonly have eye issues due to build-up of debris as they don't have eyelashes to protect their eyes. Banned from showing under the NFRS Rules due to the associated health issues, and is considered unethical to breed.​
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Reference Photos:
Lavender
Phenotype
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Genotype
​aa bb dd mm
Black + chocolate + british blue + mink
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Breeding Info
Can be prone to eclampsia and mite flare-ups.
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Reference Photos:
Marble
Phenotype
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Genotype
Mama​
1 copy Marble
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Breeding Info
​Many lines have issues with brittle teeth.
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Reference Photos:
Manx
Phenotype
​Tailless, however can be born without hips.
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Genotype
​Unknown genetics​
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Breeding Info:
​Doesn't follow typical patterns of inheritance. Banned from showing under the NFRS Rules due to the associated health issues, and is considered unethical to breed.​
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Reference Photos:
Tonkinese
Phenotype
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Genotype
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Breeding Info:
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Reference Photos:
Vari-berkshire
Phenotype
​White on belly, with variegation on sides. Will have tail stop/pied tail.
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Genotype
​Hh^e OR Hh^n
One copy of extreme allele OR one copy of notch allele
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Breeding Info
​When bred to a variegated, can help to improve coverage on back. However, can also produce more blocky markings.​
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Reference Photos:
Velveteen
Phenotype
​Wavy, dense, soft fur. Curls do not clump together. Slightly curled whiskers.
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Genotype
​Cucu - velveteen
CuCu - double velveteen
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Breeding Info:
​There isn't very much difference between velveteen and double velveteen. The "double" is perhaps the most likely to be standardised, however this is unlikely as people may then enter poor quality rexes into velveteen classes.
Dwarfs have a better velveteen coat than standards. Poorer expression in does than bucks. Longer guard hairs than non-velveteen.
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Reference Photos: