Posted by:
snakehorse
at Fri May 26 11:28:09 2006 [ Email Message ] [ Show All Posts by snakehorse ]
co-dominant or incomplete dominant?
perhaps this will help, certain traits form a basis for color or pattern (whether black or red pigment is present for example). Other traits "modify" the colors or patterns. Mutations or genetic factors can be dominant, recessive, incompletely dominant, co-dominant...and all or some are modifiers or form basic color/pattern.
The hypo trait modifies the normal pattern as well as the coloration. The extent to which it modifies the snake depends on whether the snake inherits one or two copies of this trait. This is not always the case with other mutations (ie, recessives which require the snake to inherit 2 copies or else the trait does not "appear" at all. polygenetic traits where the color/pattern if very variable and not exactly on/off like in jungle).
The hypo trait appears to lessen the black pigment and restrict the placement of the pigment (ie smaller saddles). If one "gene" or trait for this is recieved, the modification will always be "seen" or phenotypic. It can't be hidden. That's why hypo is referred to as "co-dominant". A hypo will look like a hypo, or else it is not a hypo. It's either there, or it's not. But the trait is not necessarily "Dominant" over another trait. Like Normal is dominant over albino. It's just a modifier.
Color and pattern have all sorts of modifiers. Hypo-melanism isn't the only one. So when people say it's hard to tell a "super hypo" from a "normal hypo" they are probably right. There are also incomplete dominance factors which are Polygenetic, ie, not a sure thing when inherited, variable, all over the place (like high-pink or pastel).
But take a Normal. A normal that is homozygous for normal (AA) looks just the same as the normal that is heterozygous for normal (Aa) and carries a hidden albino gene. That's because the albino gene is a true recessive. and the Normal is a true dominant.
Another comparison. Horses come in 2 colors only. Red or black. Everything else is a modification of these 2 colors. The creme gene modifies red, so a chestnut horse with the creme gene becomes a palomino (golden w/ light mane/tail). Sometimes it's hard to tell a light red horse from a dark palomino horse because there are other factors such as smutty (the addition of black hairs) which can muddy the color. Fortunately in the horse world we have a test for the creme gene (as well as for black and red). So if there is any question, the horse can be genetically tested to determine it's true genetic coloration.
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RE: co-dom vs. dominant - snakehorse, Fri May 26 11:28:09 2006