Talk:Silver dapple gene

Clarifying the Silver vs. Sooty palomino section

This passage contains spelling and grammatical errors and is not particularly relevant to the discussion of "silver mimics". This section is not about genotype, but rather describes phenotypes that can be mistaken for silver.

Therefore, I find the explanation of the palomino genotype contains extra, confusing information. Instead of focusing on the diluted quality of the palomino color (which is typoed anyhow), the sentence should show that since silvers are black or bay and never chestnut and palomino is by definition chestnut, the tones of any black-based or chestnut-based coat will reflect these chemical differences.

I propose that the sentence read "However, a true palomino, with a red-based coat, will exhibit yellow or gold tones; a silver horse, in contrast, is by definition black-based and exhibits gray, black or brown undertones."

The subsequent sentence describes the action of champagne or dun genes. It is possible to mistake chestnut-based champagnes with palominos, however the range of phenotypes does not include shades that would be easily confused with silvers. It is also possible to mistake bay duns for buckskins, which, again would not be confused with silvers. This sentence and subject matter should be left out. It is unnecessary information which will serve only to confuse all but the most educated readers.

The next sentence is a modification of a sentence which uses eye color as a way to distinguish between silver bay and sooty palomino. It has been removed from context and therefore seems to be a free-standing description of the qualities of creme dilutes. I suggest that it follow the 2nd sentence of the passage and that it state: "While a sooty palomino, like many creme dilutes, may have brown eyes a shade lighter than average, this is not true of silver dapples."

The next sentence has typos and is not relevant to the discussion. If there is no connection to silver dapple, why include it? Silver dapples do not have gold coat tones. They are not born with blue eyes that change to green, gold, or light brown, so one would be hard-pressed to confuse silver dapple with champagne. The article is not about the differences in equine eye color.

The 3rd to last sentence is a modified version of a statement that explained that palominos such as this mare [1] (she is indeed a palomino) with silver in their manes and tails are not silver. Such horses are palominos, so the qualifier "appear" is unnecessary. The 2nd to last sentence is untrue. Silver dapples do have silver streaks in their manes, but one should not assume that silver streaks mean silver dapple.

I am modifying this passage to:

"Sooty" palomino: Dark palominos may be hard to distinguish from silver dapples, particularly if the mane or tail of a palomino contain streaks of silver. A true palomino, with a red-based coat, will exhibit yellow or gold tones; a silver horse, in contrast, is by definition black-based and exhibits gray, black or brown undertones. A sooty palomino, like other creme dilutes, may have brown eyes a shade lighter than average,^[1] this is not true of silver dapples.

Countercanter (talk) 18:35, 4 April 2008 (UTC)[reply]

I like your changes, that works. I think it explains the differences. Nice! Montanabw^(talk) 04:01, 6 April 2008 (UTC)[reply]

References

^ [Locke, M. M.; Ruth, L. S.; Millon, L. V.; Penedo, M. C. T.; Murray, J. D.; Bowling, A. T.. The cream dilution gene, responsible for the palomino and buckskin coat colours, maps to horse chromosome 21. Animal Genetics, Dec 2001, Vol. 32 Issue 6, p340-343.

Congenital ocular anomalies and silver dapple

[2] Inherited congenital multiple ocular anomalies found in Rocky and Kentucky Mountain horses include: temporal ciliary epithelial cysts; iridal hypoplasia; prominent corneas; focal temporal retinal degeneration related to ciliary cysts; and, rarely, retinal detachment. Approximately 50% of these horses in Canada exhibit one or more of these conditions. The study found that horses of these breeds with the silver black and silver bay coat colors were more likely to have inherited congenital ocular anomalies. The study also suggested that silver does not cause these anomalies, but that the genes for both silver and these conditions may be physically close to one another on the chromosome (thus "linked"). The location of the silver gene may then help researchers identify the gene(s) responsible for this ophthamalogical condition.

Ocular abnormalities caused by a syndrome called Anterior Segment Dysgenesis (ASD) are segregating in the Rocky Mountain Horse breed [22,23]. An unexpected high fraction of the diseased animals in a study of 514 Rocky Mountain horses had the Silver coat color [22]. The clinical and histological signs vary from minimal to quite severe defects in the frontal part of the eye. Interestingly, many of the eye defects observed in the Silver horses are similar to those associated with congenital aniridia or malformation of the anterior segment in humans [23]. The ASD syndrome also has a relatively close resemblance to the defects observed in Small eye mice and rats [23]. Microphthalmia is well described in homozygous blue merle Australian Shepherd dogs [24]. It is hypothesized that horses homozygous for the Silver mutation have more severe symptoms of the ASD syndrome than heterozygotes [25]. The ASD syndrome is also present in the Kentucky Saddle horse and Mountain Pleasure horse breeds [26], both closely related to the Rocky Mountain Horse. However, in ASD it is the morphology of the eye that is affected and not the pigmentation. Further, in several horse breeds no eye defects have been detected among silver individuals. The ocular defects could therefore be a founder effect. This is in line with the fact that part of the horses examined for ASD could be traced back to one founder animal [23].

[3]

Countercanter (talk) 14:41, 12 April 2009 (UTC)[reply]

Clinical signs of MCOA syndrome. A. Oblique profile images of the lateral anterior segment of the right eye of a Rocky Mountain horse. A multiloculated cyst arising from the anterior ciliary body is present. B. Photograph of the right eye of a Rocky Mountain horse with ectropion uvea, dyscoria, cataract, and lens subluxation. The granula iridica is hypoplastic, the pupil is misshapen, and complete circumferential ectropion uvea is present. Nuclear cataract of the nuclear-cortical junction is present. Vitreous is present in the anterior chamber between the iris and lens secondary to posterior ventral lens subluxation. C. Profile photograph of a Rocky Mountain Horse with Cornea Globosa. Note the anterior protrusion of the cornea and large corneal diameter. D. Profile photograph of a Rocky Mountain Horse with a normal cornea. Note the normal corneal curvature and diameter.

—Preceding unsigned comment added by Kersti Nebelsiek (talk • contribs) 23:33, 12 April 2009 (UTC)[reply]

Combination colors

Grullo silver

Countercanter (talk) 13:40, 9 June 2009 (UTC)[reply]

Questionable breeds listed as having the colour

According to this chart https://www.aqha.com/media/16143/color-and-markings-4-16-14.pdf silver dapple is not an official colour in the American Quarter Horse. And according to this list http://www.shetlandponystudbooksociety.co.uk/registrations silver dapple is not an official colour in the Shetland pony. I could not find a list of accepted colours for the Swedish Warmblood. Jóna Bók (talk) 22:13, 12 November 2017 (UTC)[reply]

[1] [Locke, M. M.; Ruth, L. S.; Millon, L. V.; Penedo, M. C. T.; Murray, J. D.; Bowling, A. T.. The cream dilution gene, responsible for the palomino and buckskin coat colours, maps to horse chromosome 21. Animal Genetics, Dec 2001, Vol. 32 Issue 6, p340-343.

[1]