Dragon Offspring Calculator

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Unknown Dragon Plus Sign Unknown Dragon Equals Sign Gold Dragon
Unknown + Unknown = Gold

Total Combinations: 49

Fire: 13
Leaf: 11
Sky: 9
Blood: 7
Bone: 5
Gold: 3
Snow: 1
Grey: 0

Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Fire Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Leaf Dragon Sky Dragon Sky Dragon Sky Dragon Sky Dragon Sky Dragon Sky Dragon Sky Dragon Sky Dragon Sky Dragon Blood Dragon Blood Dragon Blood Dragon Blood Dragon Blood Dragon Blood Dragon Blood Dragon Bone Dragon Bone Dragon Bone Dragon Bone Dragon Bone Dragon Gold Dragon Gold Dragon Gold Dragon Snow Dragon

New Calculation

Colour of Father:

Colour of Mother:


This system was designed for the dragons on a planet called The Kettle, which appears in the novel Draco's Child by Sharon Plumb. She is currently (end of 2013) working on a prequel, has plans for a sequel (to the original), and ideas for more books. The stories revolve around the ideas of survival, ecological catastrophe, and dealing with fundamental changes. She has a website.

Dragons come in different "colours" depending on their genes. Dragon genetics behave like those on Earth, with each individual inheriting a set of genes from its mother and father. Like in humans, a dragon become male or female depending on whether or not it has a Y chromosome. A least I assume so; I don't remember the question ever coming up. However, dragons also have a colour gene (or group of genes) that behaves in a somewhat similar manner. The two systems operate in parallel and independantly, so both male and female dragons can be of any colour.

There are some ways that colour-selection genes differ from sex-selection genes: The dragons colours in decreasing order of gene dominance are: If a dragon has two different colour genes, it is the colour of the more dominant one. The less dominant one has no effect.
If a dragon has only one colour gene, or two genes for the same colour, it is that colour.
If a dragon has no colour genes at all, it becomes a Grey dragon, with no special abilities. Grey dragons strongly tend to the bottom of the social pecking order.

If a distinction needs to be made, a dragon with genes for only one colour can be termed a "pure _____" (e.g. pure Fire). In contrast, a dragon with a different recessive colour gene can be termed a "_____-_____ cross" with the dominant colour listed first (e.g. a Fire-Leaf cross). A Grey dragon is considered to be pure. Note that, because Snow is the most recessive colour, all Snows are also pure.

Dragons in this universe normally lay a single egg, just as humans normally give birth to a single child. I assume they can (rarely) lay two eggs, as with fraternal twins, although this is probably very hard on the mother. I do not know if egss with two yolks (the equivilent of identical twins) would not survive to hatching. This almost never happens in birds, but is not uncommon in reptiles. I don't know which class is a better approximation on dragons.

When a pure dragon mates, it always passes on its single colour to the child produced. When a cross dragon mates, it has an equal chance of passing on either one of its colour genes. A Grey dragon does not contribute a colour gene to its offspring. As a result, the child of two non-grey dragons may be a pure colour or a cross, the child of a Grey and a non-Grey is always a pure colour, and the child of two Greys is another Grey.

This program calculates the probabilities of each colour of offspring if two dragons with a known colour and unknown recessive genes mate. You can set the apparent colour of each parent, and the apparent colour distribution of the offspring will be calculated. A specific colour for a single offspring is also chosen at random with the appropriate distribution. Reloading the page will choose another random offspring colour. Note that pressing the Generate Offspring Distribution button again without changing the settings will (probably) just reload the current page from your browser cache and thus show the same result.


The colour of the child is not always obvious from the (apparent) colours of the parents. For example, a Fire-Sky cross (which appears as a Fire) and a Grey could have a Sky child. In a more extreame case, a child of the Fire-Sky cross and a Leaf-Blood cross (who appears as a Leaf) could appear to be a Fire, Leaf, or Sky. The child of two Fires with unknown recessive colours could be of any colour (except Grey).

It is usually difficult to determine which, if any, recessive colour gene a given dragon is secretly carrying. This is equivilent to the question of whether a specific dragon is a pure colour or a cross. White and Grey dragons are always pure, as is any child of a Grey dragon. A genetic test could presumably designed relatively easily if appropriate technology was available. Otherwise, the only way I can think of is through making complex tables of family lines and the colour of offspring. These tend to be complex, yeild probabilistic answers, and fail spectactualrly is a dragon's father is ever mis-identified. As a result, offspring of recessive colours can turn up unexpectedly.

Most genes for recessive colours are carried around by dragons of a different colour. Lets assume colour genes exist in equal frequencies (unlike in real genetics). In that case, only 1/7 ≈ 14% of the Snow colour genes are carried by Snow dragons. The other 6/7 ≈ 86% are carried as recessive genes by dragons of other colours. At the other extreme, all Fire genes are carried by Fire dragons.

The distribution of dragon colours is not remotely equal. If we assume equal numbers of colour genes as above, the ratio is:

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