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Pien
Ji Shih Tzu-
Where Type Meets Temperament |
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Normal Pigment, Livers & Blues in Shih TzuThere is a lot of confusion regarding dogs of normal pigment, livers, and blues. For the purpose of this discussion, we are going to concentrate on two gene series- B and D. We are discussing skin pigment, not coat color. The genes in this discussion have minimal impact on coat color, though there definitely is some. B SeriesIn Shih Tzu, the points (eye rims, nose, lips) are always first controlled by the B series gene. The B series has two color possibilities- Black (B) or no black (b- liver). BB (the homozygous state for black, homozygous meaning two of the same gene) is black points and can only produce black pointed offspring because B is dominant, and all offspring will carry a B (the other side of the gene pair will carry a gene from the other parent). Bb (the heterozygous state) will be black pointed, but can produce either black or liver pointed offspring. bb (again homozygous, but this time for liver) is always liver pointed. The offspring can be liver or black, but ALL will carry b (liver) and be able to produce it. The skin of the bb, or liver, dog cannot support black pigment. This dog will have a liver nose, varying in intensity from red-tan to chocolate, and there will be no black on either the skin or coat. D Series The Maltese Dilute (D series) gene modifies the base color- black or liver- with a grayish blue like you see in Maltese and Russian Blue cats. The dominant side of the gene (D) is actually non-blue-dilute, and does not affect pigment. DD will not have blue-dilute pigment, nor will any of the offspring be blue-dilute. Dd does not affect pigment, but a blue-dilute offspring may be produced. dd is blue-dilute pigmented, and will always pass a blue-dilute gene to offspring, so they will either be blue-dilute or carry it. B/D Interaction Here’s where it gets interesting! When you see a dog that is a clear, easily to identify blue, it is likely that the blue-dilute gene is active over liver- one gene pair being bb and another dd. When blue-dilute is active over black points (BB with dd or Bb with dd), it becomes much harder to distinguish. Many people confuse the transmission of blue with that of liver, and think that a blue dog cannot support black pigment, and this is true, to a point. Remember that when you have blue-dilute over black, the black will be diluted to blue. Over good, black pigment, dilution can produce a strong gunmetal color in the hair that is VERY difficult to distinguish from undiluted black, and for all intents and purposes appears black, though you notice it shines blue in the sun! How Do I Recognize Blue when it is over Black? This can be a very difficult task! Many a blue with excellent pigment for a blue is mistaken for a normal pigmented dog with poor pigment, and left out of the points for no reason! First, look at the pigment on the lips. In a blue over black, this will take on a lavender tint. When you see this, look CLOSELY at the nose. On a normally dark pigmented dog, the nose will look normal until you really look. There will be a blue-gray cast to the skin on the nose, sometimes so dark that it is difficult to see until you are out in sunlight! (If you are judging inside and in doubt, ask the owner- they should know! Remember blues are legal and no preference should be given for color!) The rims of the eyes will have the same lavender cast. Do not be fooled by eyelashes or eye stripes that look black- they may be a gunmetal color so dark you will not spot it except for the blue shine produced in direct sunlight. Hopefully this will help clear up some confusion! |
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