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"Comments by Sheila Schmutz on the Dun Gene in Dexter Cattle"

In May 2005, I e-mailed Sheila Schmutz in order to confirm my understanding of the findings of her research on the gene for dun coat colour in Dexters.

I asked: "Is it possible to conclude from your research that the Dexter dun gene has so far not been found in any other breed (your article, for instance, refers to 18 other breeds examined)?"

Sheila replied: "Correct (although it is the allele that is unique really). All cattle have a TYRP1 gene, just not this version (copy, allele) of this gene."

I asked: "Does this mean that the Dexter dun gene has not come about through introgression - i.e., from a dun gene from another breed which has been introduced into the Dexter gene pool?"

Sheila replied: "As a scientist you know I can strictly only say it didn't come from the 18 other breeds we studied, but I do believe this mutation occurred in the Dexter or an ancestral breed which may or may not still be around."

I asked: "The dun gene is recessive thus requiring its presence in both parents for an offspring to have the chance of being dun?"

Sheila replied: "Yes, to be dun, each parent must have at least one 'b' allele and pass it on to the offspring."

I asked: "It appears that genes on two different chromosomes are involved in the basic coat colour for Dexters. If the gene on chromosome 18 is red/red, then will this suppress the expression of dun when dun/dun is present on chromosome 8?"

Sheila replied: "Yes, [for dun coat colour to occur] it is necessary that eumelanin pigment is made and then the TYRP1 genotype 'b/b' [dun/dun] alters that biochemically from black to brown. Cattle who have 'e/e' [red/red] on chromosome 18  make phaeomelanin primarily and are red, so if they are 'e/e,b/b' they will still be red.

I asked: "John Potter was an important contributor to your research?"

Sheila replied: "Yes, John is the one who had this hypothesis about dun originally and helped us find many cattle to test."

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