Frequently individuals question whether their reptile is a morph or not. The purpose of this article is to explain what defines a morph. Their are two requirements in identifying a morph; appearance and inheritance.
Distinct Color or Pattern Compared to the Wildtype Phenotype
The Wildtype (or Normal) appearance of any species of reptile can be highly variable. Slight differences in color and pattern are not uncommon. To be defined as a morph, their must be a significant difference in the color or pattern of the animal in question. For example, comparing a Cinnamon Ball Python to its Normal counterpart, you will note that a Cinnamon has increased brown pigmentation, chocolaty in appearance, increased flame pattern on its sides and key-hole or tear drop markings.
Genetic Inheritance
Determining if the look is reproducible is the second and most important topic on classifying whether it is a morph or not.
Simple Recessive
A gene that is phenotypically expressed in the homozygous state but has its expression masked in the presence of a dominant gene.
So what does this mean? A recessive mutation will only be reproduced if both parents are expressing or carrying the morph gene. To determine by breeding trials whether or not the mutation is simple recessive, the morph must be bred to a Wildtype. Retain the offspring from the pairing, raise them up to breeding size and then breed them back to the morph parent. This is easiest done when you have a morph male to breed back to his daughters.
Co-Dominant
Relationship between two alleles where both are expressed equally when heterozygous to each other, resulting in three phenotypes; Wildtype, Heterozygous and Homozygous. Red + White = Equal Parts Red & White.
So what does this mean? A co-dominant mutation can be reproduced if one parent is heterozygous or homozygous for the mutation. To determine by breeding trials whether or not a mutation is co-dominant, two breeding trials are necessary. First, the heterozygous needs paired with a Normal, if the mutation is co-dominant, the morph will be reproduced in the first generation (f1). To determine if the homozygous phenotype is different then the heterozygous, the f1 morphs produced from the first generation should be held back, raised up to breeding size and bred back to the morph parent. If the second generation (f2) produces a homozygous that is phenotypically different then the heterozygous (and the heterozygous phenotype is a equal expression between Wildtype and the Homozygous), the morph is co-dominant.
Incomplete Dominant
Relationship between two alleles where both are expressed in a blending when heterozygous to each other, resulting in three phenotypes; Wildtype, Heterozygous and Homozygous. Red + White = Pink.
So what does this mean? An incomplete dominant mutation can be reproduced if one parent is heterozygous or homozygous for the mutation. To determine by breeding trials whether or not a mutation is co-dominant, two breeding trials are necessary. First, the heterozygous needs paired with a Normal, if the mutation is incomplete dominant, the morph will be reproduced in the first generation (f1). To determine if the homozygous phenotype is different then the heterozygous, the f1 morphs produced from the first generation should be held back, raised up to breeding size and bred back to the morph parent. If the second generation (f2) produces a homozygous that is phenotypically different then the heterozygous(and the heterozygous phenotype is a blending expression between Wildtype and the Homozygous), the morph is incomplete dominant.
Dominant
Relationship between two alleles where both are expressed in the heterozygous and homozygous phenotype. Their is no visual difference between the two expressions, resulting in only two phenotype.
So what does this mean? An dominant mutation can be reproduced if one parent is heterozygous or homozygous for the mutation. To determine by breeding trials whether or not a mutation is dominant, two breeding trials are necessary. First, the heterozygous needs paired with a Normal, if the mutation is dominant, the morph will be reproduced in the first generation (f1). To determine if the homozygous phenotype is different then the heterozygous, the f1 morphs produced from the first generation should be held back, raised up to breeding size and bred back to the morph parent. If the second generation (f2) does not produce a homozygous that is phenotypically different then the heterozygous, the morph is dominant.
Selective Breeding
Breeding program which has a goal of reproducing or enhancing a particular look found in the parents.
So what does this mean? A selectively bred mutation is developed by spending several generations refining a particular look, breeding like animals together to achieve a goal in color or pattern. One of the best examples of this is the Candycane in Cornsnakes. Enthusiasts have spent years developing the mutation for a crisp white background and bright red or orange saddles. The key to selectively bred morphs is the understanding that by breeding them to unalike morphs you are diluting the goal look. Using the Candycane example, if you breed to a standard Amelanistic, the resulting offspring will be lower quality examples of the morph.
Variances to the Genetic “Rules”
One of the blessings of working with nature is that she will do as she pleases and does not always follow the rules defined by science. So in turn, science has to bend to fit her wants. Co-Dominant, Incomplete Dominant and Dominant are not necessarily always reflected in comparison to the Wildtype. While this makes for some excitement in the morph world, it can cause a lot of confusion.
In Cornsnakes, Ultra and Amel are recessive mutations, however Ultra and Amel are also Co-Dominant to each other. What this means is that Ultra and Amel are Alleles that are located on the same Locus in the genetic code of Cornsnakes. The result of a Cornsnake that carries an allele for Ultra and an allele for Amel is a phenotype that expresses the two mutations in an equal blending, Ultramel.