Dragon Offspring Calculator
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Blood + Sky = Sky
Total Combinations: 63
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. (At least I assume so; the question never 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 independently, 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:
- You can have at most one Y chromosome, which can only be inherited from the father. However, a dragon can (and normally does) inherit two colour genes, one from each parent.
- A Y chromosome, if present, is always dominant. Most colour genes can be either dominant or recessive.
There is only one type of Y chromosome. This allows for 2 variants of human (or dragon):
In contrast, there are 7 possible colour genes with a fixed order of dominance and only the dominant one affecting the dragon's development. This allows for 8 colours (see below).
- The base (female) form that you get by default
- The modified (male) form that you get if you have a Y chromosome
- A Y chromosome, if present, significantly changes your anatomy. It changes both primary sexual characteristics (where entire body parts are added or removed) and secondary sexual characteristics (where existing body parts are adapted to focus on different tasks). In contrast, colour genes only produce "secondary" characteristics, adapting the dragon's existing abilities.
- If you do not get a Y chromosome, you get an extra X chromosome from your father instead (giving you two, like with every other chromosome). In contrast, a dragon can be simply missing one or both colour genes with any serious ill effect.
If a dragon has two different colour genes, it is the colour of the more dominant one. The less dominant one has no effect.
- Fire: These dragons have hot fire, shorter wings allowing for faster turns, and a desire for adventure.
- Leaf: These dragons have dexterous claws, imagination, and a strong nurturing instinct.
- Sky: These dragons long, broad wings especially suitable for soaring, and keen eyes.
- Blood: These dragons especially large and strong.
- Bone: These dragons have keen ears, a good sense of smell, and the ability to extract knowledge from the bones of dead dragons.
- Sun: These dragons have cleaver minds.
- Snow: These dragons are small and can occasionally see visions.
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 an Ash dragon, with no special abilities. Ash 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). An Ash 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 eggs with two yolks (the equivalent 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. An Ash dragon does not contribute a colour gene to its offspring. As a result, the child of two non-Ash dragons may be a pure colour or a cross, the child of an Ash and a non-Ash is always a pure colour, and the child of two Ashes is another Ash.
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 an Ash could have a Sky child. In a more extreme 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 Ash).
It is usually difficult to determine which, if any, recessive colour gene a given dragon is secretly carrying. This is equivalent to whether a specific dragon is a pure colour or a cross. White and Ash dragons are always pure, as is any child of an Ash dragon. A genetic test could presumably be 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, yield probabilistic answers, and fail spectacularly is a dragon's father is ever misidentified. 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. Let's 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:
- 13 Fire
- 11 Leaf
- 9 Sky
- 7 Blood
- 5 Bone
- 3 Sun
- 1 Snow
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