Let's talk about some of the terms first. Genetics can at first seem confusing because some of the terms refer to different
things that may seem to be the same.
One of the first things that needs to be clearly identified is the meaning of the terms "genotype" and "phenotype" and of course "morph".
Genotype is the genetic makeup of an organism, either at a single locus on the chromosome or over all its genes collectively,
The genotype of an organism directly and indirectly affects its molecular, physical, and other traits.
The phenotype is this composite of an organism's observable characteristics or traits. The physical expression is what we commonly refer to as its morph, which is short for morphology.
Remember, there can also be an outwardly unseen expression of an organism's traits, blood type, sensitivity to foods, etc. These maybe chemical, physiological, even psychological (agressive, etc)
In this discussion of Bearded Dragons genetics we are mainly concerned with their outwardly visible morphology.
Thus for our purposes phenotype = morph and genotype = genes!
There are two copies of most genes, one from female and one from male parent.
These genes can come in different versions, called alleles.
An allele is the variant form of a given gene. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation.
a diploid organism is one that has pairs of chromosomes with genes, usually one from each parent. If two alleles of a given gene are identical at the same or corresponding loci,
the organism is called a homozygote and is said to be homozygous with respect to that gene;
Heterozygous (Het - short for Heterozygote or Heterozygous):
if the two alleles of a gene are different at the same or corresponding loci,the organism is a heterozygote and is heterozygous.
If a trait in question is dominant, a het will express (visually) only the trait coded by the dominant allele and the trait coded by the recessive allele will not be expressed visually, yet can be passed on to offspring.
At heterozygous gene loci, the two alleles(genes from each parent) interact to produce the phenotype.
In complete dominance, the effect of one allele in a heterozygous genotype completely masks the effect of the other.
The allele that masks the other is said to be dominant to the latter, and the allele that is masked is said to be recessive to the former.
Complete dominance therefore means that the phenotype of the heterozygote is indistinguishable from that of the dominant homozygote.
p>Co-dominance occurs when the contributions of both alleles are visible in the phenotype.
Incomplete dominance (also called partial dominance or semi-dominance)
Incomplete dominance occurs when the phenotype of the heterozygous genotype is distinct from
and often intermediate to the phenotypes of the homozygous genotypes.
For example, the snapdragon flower color is homozygous for either red or white.
When the red homozygous flower is paired with the white homozygous flower, the result yields a pink snapdragon flower.
The pink snapdragon is the result of incomplete dominance.
Less commonly, the presence of a single functional allele gives a phenotype that is not normal(Leatherback) but less severe than that of the non-functional homozygote(Silkback or Silkie).
This occurs when the functional allele is not haplo-sufficient. The terms haplo-insufficiency and incomplete dominance are typically applied to these cases.
The intermediate interaction occurs where the heterozygous(Het) genotype produces a phenotype intermediate between the two homozygotes.
Depending on which of the two homozygotes the heterozygote most resembles, one allele is said to show incomplete dominance over the other
Leatherback is incomplete dominance over standard scalation.
One thing to keep in mind is that dominance is only important in how it affects the trait.
Terms like recessive, dominant, codominant, and incomplete dominance all refer to the trait (phenotype),
not the set of genes we have (genotype). A gene may be dominant to one gene and recessive to another!
There are different terms used to describe the color, or lack thereof, in bearded dragons.
The latin prefix 'A' or 'An' means without/no. 'Hypo' means less. 'Hyper' means more.
Melanin - Black
Amelanistic - No black pigment
Hypomelanistic - Less than normal black pigment
Xanthinin - Yellow
Axanthic - No yellow pigment
Hypoxanthic - Less than normal yellow pigment
Erythrinin - Red
Anerythristic - No red pigment
Hypoerythristic - Less than normal red pigment
Hypererythristic - More than normal red pigment
With these definitions in mind we can now discuss the genetics of Bearded Dragons
Pattern Altering Mutations
- Genetic Stripe - Co-Dominant
- Tiger - Dominant
- Paradox - Recessive
- Witblits - Recessive
- Zero - Recessive
A bearded dragon's normal patterning consists of bands of color that run from side to side along the back and tail. Typically the back looks like tiger stripes and the tail looks like bars.
The mutations in this section cause changes in this normal patterning. Back to top.
Genetic Stripe New
This is a relatively new trait. It s the fusion of the column of dorsal ovals, resulting in two stripes down the back of the Dragon. The ultimate form being two straight racing stripes down the back of the animal.
It is Co-Dominant and when mixed with other dorsal patterns may exhibit a variety of appearances. With pastels you get the perfect stripes. With the Tiger pattern you get stripes with ladder like thin cross bars. As with
many Bearded Dragon Patterns the colors may fade with age and the stripe may be difficult to distinguish from the background. This genetic trait appears to have been isolated by several breeders throughout the world, in Europe, Asia, and the United States.
Tiger or Tiger Stripe
The tiger pattern looks like a tigers stripes, thick and dark horizontal lines across the dragon's back.
Witblits is a recessive mutation. It was discovered relatively recently, and causes the dragon to be one solid color with no stripes, spots, or other patterning.
Witblits dragons are a tan, sandy color.
Zero is a recessive mutation that was discovered relatively recently. Like Witblits, the zero mutation causes the dragon to be one solid color with no stripes, spots, or patterning.
Zero dragons are an elegant silver color.
Like color morphs, paradox is not caused by any one specific mutation. It is the result of several genes working in combination. Paradox dragons are identified by irregular,
non-symmetric blotches of color that can appear anywhere on their body and are not explained by any other known mutation. Paradox dragons are some of the most visually interesting dragons available.
Scalation Altering Mutations
The Leatherback Mutation Family
Leatherback is a family of three separate mutations that all have the effect of reducing the size and number of spikes.
The first leatherback mutation was discovered by a breeder in Italy and was referred to as the Italian leatherback. At a later date, a mutation that is believed to be separate was discovered by an
American breeder and was referred to as American leatherback. At first the American Leatherback was weaker than the Italian and frequently did not live long. This was eventually remedied by selective breeding.
Today these two mutations are indistinguishable from one another and are collectively referred to as leatherback.
Leatherback is a co-dominant mutation. Dragons that are heterozygous for leatherback do not have any spikes on their back or limbs. They have one row of spikes on each side of their body, and
they also have spikes on their head and neck. Their back and limbs are covered with smooth scales that are uniform in size. Dragons that are homozygous for the leatherback mutation are called
silkback which is described further below.
It is sometimes claimed that Italian leatherbacks have a completely smooth back and American leatherbacks have two rows of small spikes on their back. This is not accurate.
Some leatherback dragons have two rows of small spikes on their back, but this is caused by the influence of other genes. Breeding these dragons can produce offspring that have completely smooth backs and visa versa.
The American and Italian mutations are most likely mutations that occurred in the same gene and have the same effect. They may even be genetically the same.
A recessive form of leatherback also exists, which causes the same elimination of spikes on most of the dragon's body as the co-dominant forms of leatherback. There is no visual distinction between any of
the three forms of leatherback. The only way to determine if a leatherback dragon possesses the recessive form is through breeding the dragon and observing the results.
Silkback or Silkie
Dragons that are homozygous for either of the incomplete dominance forms of leatherback are referred to as silkback. Silkbacks cannot result from the recessive leatherback mutation.
This means that the two Incomplete dominance leatherback mutations are different mutations of the same gene. Silkback dragons have skin with no spikes or scales anywhere on their body.
The complete absence of scales gives silkback dragons a very unique appearance, which some people find interesting and others find unsettling, and unappealing.
Silkback dragons have delicate skin and benefit from regular soaks to assist in shedding. Female silkbacks should not be used as breeders, as their skin is easily injured during mating.
Male silkback dragons, however, can be bred without issue. It is best to not even house female silk back dragons with other females, as the mild aggression that females can show
towards one another that do not injure a regular bearded dragon, can injure a silkback dragon due to their lack of protective scales.
Microscale is the most common mutation that I see being inaccurately advertised by other breeders. Most of the dragons that I have seen advertised as Microscale are not.
Microscale dragons are produced by combining the recessive leatherback mutation with the Incomplete dominance leatherback. The result of this combination is a dragon that develops spikes only on its head and beard.
A leatherback dragon has one row of spikes running down each side of its body, as well as spikes on its head and beard. A Microscale dragon does not have any spikes on its body.
The row of side spikes is completely eliminated, and the spikes on the head and beard are reduced to being not much larger then the rest of the scales. The identifying characteristics of microscale dragons are
not widely understood, which leaves buyers vulnerable to false advertisements. If a bearded dragon has any spikes running down the side of its body then it is not a microscale. .
Dunner is a dominant trait that alters the dragon’s patterning and the direction of the scales. The dunner mutation causes the pattern direction to run from head
to tail instead of from side to side, and forms spots instead of stripes. Dunner dragons can also be quickly identified by the direction of their scales.
The scales of a non-dunner dragon are neatly arranged and run from head to tail. The scales of a dunner dragon have a less organized arrangement and point towards the sides.
This is most noticeable on the beard and belly. Dunner dragons have the unusual tendency to store their food in the back of their throat before swallowing it.
Hatchlings that eat too much food at once or prey that are too large may vomit their food back up several hours later due to this odd eating habit.
With a proper diet, hatchlings quickly outgrow this issue. Eliminating this behavioral issue from hatchling dunners is one of our priorities at our breeding facility.