Temperature Sensitive Gene - Himi

 

 

 

Pointed white English Angora buck Chu's Higgins in March 1988 when the weather was cool.

Pointed white English Angora buck Chu's Higgins in August 1988 when the temperature was hot.

Betty says,

 

In 2007, I wrote a post about my experience with raising pointed white English Angora, see

 

http://ncag.blogspot.com/2007/08/pointed-white-english-angora-so-cute-so.html

 

The pictures of Chu's Higgins were used, and I am repeating these two photos here.   As you can see that Higgins had nice black points in March 1988 when he was young and when the temperature was cool.   Five months later when the summer came, his black points turned lighter than blue or lilac.

 

It is well-known that the Himi gene c(h) is temperature sensitive.   In Biology, Concepts and Applications 7th edition by Starr/Evers/Starr, it discusses a heat-sensitive enzyme called Tyrosinase that affects the Siamese cats and Himalayan rabbits.  I quote:

"The rabbits are homozygous for the c(h) allele which encode a form of Tyrosinase that does not work if the temperature exceeds 33C or 91F.  Metabolic heat keeps the main body warm enough to stop the enzyme from working so the fur is light there.  Ears and other slender appendages lose metabolic heat faster and are cooler so melanin darkens them".    

  The Tyrosinase enzyme affects the fur color, not the skin or the nails.   The section also animates an experiment of shaving off a himi marked rabbit then put on an ice pack, the fur grows back dark.   It is the fur that is affected by the temperature, not the nails.
 

   To read a more detailed description, go to:

 

http://books.google.com/books?id=EXNFwB-O-WUC&pg=PA163&lpg=PA163&dq=heat+sensitive+color+in+rabbit&source=bl&ots=FpBj4ZaUHv&sig=VW9_vXUYS08WX0niD1JYvlh-mtY&hl=en&sa=X&ei=wgirU-HuCNityASy6YD4CQ&ved=0CFcQ6AEwDA#v=onepage&q=heat%20sensitive%20color%20in%20rabbit&f=false 

 

If the page does not load to the exact topic, go to10.6 Genes and the Environment on page 163.

 

The pointed white Angoras carry either two himi genes c(h) or one himi gene c(h) combined with one REW gene c.   No other colored rabbits, not tort, not black, not chestnut, not fawn, not sable, not any other color is heat-sensitive.  One may be confused about the torts vs. himi thinking that the torts also have darker points and lighter wool on the body.   The reason for tort to have lighter body wool/fur is due to the non-extension gene ee that does not extend the darker color to the rest of the body.

Heat-sensitive gene c(h) is on the C allele while the non-extension ee is on the E allele, they are not related.

One more thing: the himi gene c(h) fades the point color during the hot temperature because it is harder for the extremities to cool down during the summer, the nail colors are not affected by the heat.  If the nails match, they match in the winter and they still match in the summer.