Logo header

BASIC GENETICS

Havanese are uniquely different from other breeds in many ways. One of the most intriguing of these is coat colour. Few, if any other breeds, carry such a wide range of colour shades and patterns in their coats as the Havanese. Havanese are renowned as a breed which carries a large majority variety of the colours and variants possible in dogdom. They come in black, silver, chocolate, brindle, sable, red, gold, champagne, cream and white displayed as a single solid colour or in assorted combinations. Not only is this vast array possible, the effects of an assortment of modifying genes result in endless variations. The possibilities are mind boggling. There is probably no area of the breed which rivals colour for intrigue and confusion.

litterIf your chosen breed is a Maltese; it's a given that your puppy will be white. White sire + white dam = white puppies. That one is easy to understand. Now, let's move on to the Havanese. Two parents of different colours may produce 5 puppies in a litter, each a different colour from themselves and from their parents. As one breeder put it "Havanese litters can look a basket of Easter Eggs". No wonder confusion reigns. It's easy to understand why so many people believe that Havanese colours are erratic and completely unpredictable. Many people understand the basics of genetics, but once the talk turns to alleles, locus, series, expression, partial dominance, recessives, modifiers, polygenic traits, etc, our understanding gets a lot foggier. So, let's start with the basics.


chromosomesChromosomes are the structures that hold genes. Genes are the instructions. There are many different genes to blueprint every part of a living being (including colour). Individual genes each have a specific spot on the chromosome that is its home. Home-base for a gene is called a gene locus. Next we need to know about Alleles. Those are the different expressions of a gene. Each gene may have a few variations (alleles) or many, arranged according to an order of dominance. Even though a locus may have several allele possibilities, each living being only gets two, one from Mom and one from Dad. There are at least 10 different genes (likely more) that control colour in the Havanese. There are likely many more genes at play than those known or currently theorized about. Much of published colour research is based on hypotheses and theory based on what is observed in assorted breeds of dogs. Not nearly as much is based on actual DNA data though studies in the DNA arena are progressing and revealing that there are many more genes involved than previously hypothesized and that the actual number of alleles on any given gene may be very different than what is currently believed. There is still much to learn and discover. Different genes control different parts of the coat colour. Some genes make the different colour pigments while other genes control the distribution of these pigments within the individual hairs and all over the entire body.

Dogs have two kinds of pigment possible in their coats; dark pigment called "Eumelanin" and light pigment called "Phaeomelanin". In the world of genetics, any dog that has a predominantly eumelanin (dark) pigmented coat is referred to as "black", whether the coat is black, brown, charcoal, silver, etc. . In the same way, any dog that has a predominantly phaeomelanin (light) pigmented coat is referred to as "yellow" even though the actual colour of the dog may be red, gold, tan, champagne, cream, etc. Some genes affect just the dark pigment, others just the light pigment and some affect both.

We also need to know about phenotypes and genotypes. A phenotype is what the dog looks like in appearance, while genotype is the non-visible genetic code responsible for making what you see (the recipe). In some cases, there may be more than one gene code that gives the same appearance. Think of it like math. The answer (phenotype) is 4. There can be many different formulas (genotypes) to get to that same answer; 2+2, 1+3 , 5-1 and so on.

dominance

Dominance: All the alleles are not equal. They are arranged in order of dominance. For example: on the C locus: [ C ] is dominant over all the other alleles that follow; [ cch ] is second in line. It is recessive to [ C ] but still dominant over
[ c ce ] and so on. In simple dominance, if there are two dominant genes, the dominant is expressed. If there is one dominant and one recessive, the dominant is again expressed and the recessive will be hidden. The recessive gene will only be expressed if there are two recessives. In cases of incomplete or partial dominance, the dominant only partially covers rather than totally obscuring the recessive. These genes and the different ways they interact with each other are responsible for the wide range of shade variety and range of blended expression that we see.

In naming alleles, capital letters are used for the ones considered dominant and lower case letters are used for ones considered recessive. The letter itself tells you which locus it is found on. For example, anything called [E] or [e] belongs on the E locus. Those little letters that are superscripted in the allele names are not nearly as confusing as they first appear and make sense if you look closely. They are variations which can be either dominant or recessive. If the superscript is attached to an upper case or capital letter, then it is a dominant variation and if attached to a lower case letter, then it is a recessive variation. Here are a few examples to look at.
at (t = Black and tan)   ay (y = yellow)  cch (ch = chinchilla)   ce (e = extreme)   kbr (br = brindle)  ssi (si = irish spotting)  sp (p = parti)

We will look at the ten genes that are considered most significant in Havanese colour. Those are A, B, C, D, E, G, K, S, V and T.

Are you ready? Let's take a closer look ...