As many of you may know, we are undergoing genetic DNA testing to determine on which gene the curl on our cats lies as well as to determine if indeed ours is a different gene than that of the other “curly” cats.  We know beyond any shadow of a doubt that the gene is different from both the Devon and Cornish Rex breeds as theirs is a recessive gene and ours is a dominant gene.  It has been proven that the Devon and Cornish genes are different from each other in that when a cat from each breed is bred to the opposite, straight haired kittens are produced.  It is therefore impossible that the two breeds have the same mutation.  There are two other breeds with curly hair that are dominant genes, the American Wirehair and the Selkirk Rex.  Our aim is to prove that we are indeed “different” from these other breeds.  That would not only mean structurally different, but specifically a difference in the curl itself.  There is the possibility that these breeds could all be sharing the same gene but that it is manifesting in a different manner.  There are many different means by which this gene might manifest, all of which are beyond the scope of my ability to explain, as I am not a geneticist.  We cannot utilize the same methods of proving our genetic diversity, as did the Devon and Cornish people.  The three other breeds have a dominant gene and would therefore not have the same response, as did the Devon and Cornish recessive genes if they were bred together.  Our only alternative is to do genetic DNA testing.  There are a few of us who are testing all of our cats in order that we may lay the issue to rest once and for all.

Perhaps at this point it would be wise for me to offer a few definitions that may help in the process of learning some genetic terms.  I know that many of you are well versed in genetics, but there are a few out there who have never bred before and it is up to the rest of us to help our “soul-breeders” in their trek to discover all they can about breeding.  My attempt here is to keep this as basic as possible and to use lay terms in order that I might better help others learn.  I do not pretend to be an expert and only wish to share what little knowledge I have.  I relate things in my own terms as to my own understanding.  Hopefully my thoughts on the matter are correct.

Gene: The basic unit of heredity.  The gene contains DNA and each one will occupy a certain place on a chromosome.  A gene is capable of undergoing a “change” under the right circumstances, thus producing a new trait.  This is called a “mutation” (a mutation is what produced our LaPerm coats).  Hereditary traits are controlled by pairs of genes that are in the same place on a chromosome.  One gene would come from each parent to form the pair.  These pairs of genes can both be dominant, both are recessive or there can be one dominant and one recessive.  In the case of one dominant and one recessive, the dominant trait will show up and the resulting progeny will be “heterozygous”.  In the case of two recessives, the recessive gene will appear in the progeny and in the case of two dominants; the dominant trait will obviously appear.  In both of these last two cases the progeny is “homozygous” for that trait.

Homozygous: Both genes (one from each parent) in a pair that carry the same trait.  In the case of our LaPerms to be homozygous for the curl the progeny would have to come from two curly parents and get a “curly” gene from each parent.  In this case, all curly kittens would come from a mating with this animal when bred to one with straight hair.  It should be noted that such breeding would produce all heterozygous kittens, as each would get the straight haired gene from the straight haired adult.

Heterozygous: Two genes in a pair that carry different traits.  The dominant trait will appear in this case.  To be certain an animal is heterozygous for our curl, one parent would be curly and one straight haired.  If both parents are curly then breeding the animal to a straight haired animal can produce either all curly or some of each type.  Producing both types would determine the animal to be heterozygous.  It should be noted that producing all curly kittens from a similar breeding would not prove the animal homozygous as it may take several such breedings for the straight haired trait to manifest.

Chromosome: A linear thread made up of DNA (and proteins) in the nucleus of a cell.

DNA: The genetic code for the cell.  Contains all the genes for an organism and is the chemical basis for heredity.

Cell: The structural unit for all living matter.  They make up to tissues of the body and carry out all bodily functions.

Dominant Gene: This would be a trait or characteristic that expresses itself in the progeny of breeding although only one parent may carry the gene.  As in our curly coats, only one parent has to be curly in order that we produce curly kittens. In other words, you have to see it to get it.

Recessive Gene: A trait or characteristic that can “hide” (or recede) in the background.  It would require both parents to carry this gene in order that it is produced in the progeny.  This gene would “lack control” and not be dominant.  Recessive genes can carry over many, many generations before showing up, giving us the impression they do not exist.  Wrong!

Color genes can also be dominant or recessive.  There is another term that should be noted in the realm of color and that is the dilute gene.  Dilute means to “weaken” the color (such as bleaching your hair).  The dominant color gene is black (or seal in the case of pointed cats).  Recessive to the black is brown or chocolate.  This is not to be confused with “brown tabby” as a brown tabby cat is actually a black cat with a tabby pattern.  Our patterns are in yet another realm of the mysterious.  To produce a dominant color or pattern, one parent must be of that color or pattern.  The recessive colors or patterns can be carried and/or masked by the dominant but the reverse is not true.

Chocolate would be dominant over cinnamon but yet recessive to black.  Cinnamon is the most recessive full color.  It would require two cinnamon genes to produce a cinnamon cat where a black cat can carry another color, chocolate or cinnamon but not both.  Chocolate can carry cinnamon whereas cinnamon is homozygous.  Both black and chocolate can be homozygous or heterozygous.

When the color gene is weakened we get the dilute colors.  Blue is the dilute color of black, lavender is the dilute color of chocolate and fawn is the dilute color of cinnamon.  In order to produce the dilute colors the progeny must get a dilute gene from each parent.  Be aware that both parents can be the undiluted or “full” color and still produce the dilute kittens.  This is again the case of dominant and recessive genes.  The full color is a dominant gene where the dilute color is recessive.  There are 3 genes that select for coat color, one for the actual color, one for the shade of the color (full or dilute) and one for the pattern.  The order of dominance for the dilute colors is the same as for the full colors; blue is dominant over lavender and lavender is recessive to blue but dominant over fawn.

Think about this one; a blue parent not carrying the chocolate (or cinnamon) gene and a chocolate parent not carrying the dilute gene (or cinnamon) …all of the offspring will be black!  To understand this you must realize that the blue cat is indeed a black cat with the color weakened.  Since it does not carry the chocolate, then it cannot produce chocolate and since the chocolate does not carry dilute it cannot produce dilute kittens, thus all kittens are black.  Remember though that each of those black kittens’ carries dilute and chocolate.  If you remember that each kitten gets one gene from each parent, then you can make yourself a chart and figure out what the likelihood of producing certain colors and/or patterns is.

As to pattern, we have several to choose from.  The most dominant pattern gene is the agouti-ticked cat.  This is the same pattern as we see on a squirrel or a jackrabbit and is common to the Abyssinian and Somali.  The order of dominance in our patterns is as follows: Agouti-ticked, spotted tabby, mackerel tabby, classic tabby, solid and finally pointed cats are the most recessive.  Any one of the first cats can be heterozygous for pattern but the pointed cats are homozygous for pattern. 

Other factors involved in color are the “O” gene, which is sex-linked and produces our red tabby cats (some think of the red tabby as the orange cat).  Cream is the dilute of red.  This is where we also get our tortoiseshell cats.   As a sex-linked color, the red (or cream) will produce two colors (other than white) on female cats.  It is extremely rare for a male to have two colors unless there is some sort of genetic mutation.  This gene is carried on the X chromosome only and is a dominant gene.  You therefore must have red on one parent (or a parent with red on it such as a calico) to produce red kittens.

The white (W) gene masks other colors and produces white areas on the cat.  This is independent of the other colors and again is a dominant gene.  A solid white cat will generally carry another color under the magnificent white coat.  Often a spot of color will be on the head of a cat showing the color being masked.  There are several patterns involved with the white spotting from mittens or a locket at the throat to the solid white cat.

The silver gene is the last consideration in colors.  This is called the “inhibitor” gene as it inhibits (or suppresses) the color pigment on the hair shaft.  Thus you get the silver background color with the intense darker pattern on top.  The inhibitor gene is another example of a dominant gene and therefore one parent must be silver in order to get kittens with the silver color.  The “smoke” is a variation of the silver gene as well but rather than on a patterned cat, it will be on a solid colored cat.  This result is that the cat is silver next to the skin and tipped with another color.  A beautiful effect!

There are many more aspects to color and pattern not mentioned here.  Many good books exist from which you can learn in more detail.  Mine is simply an attempt to verse you in the possibilities that exist and to give you an idea of what you can expect when putting two animals together.  We did publish a four part article on color genetics in the four 1999 issues of the LPSA newsletter.

The important issue on color to remember is that if it is dominant, you must see it to get it whereby the recessive can hide from you.  From this I like to remind people to go back to kindergarten and get out your crayons.  If you make a black mark you cannot cover it up with the other colors.  If you make a chocolate or cinnamon mark you can cover them up with the black.  Thus the dominant color “hides” the recessive.  The recessive can hide for many, many generations and then jump out and surprise you.  Sometimes it is like an Easter basket to see all the possibilities.