this is what i have learnt about genetics so far.. and how they work and i have written on a spare sheet of paper in my time to try and explaing this in a simple language... enjoy. if i make any mistakes please correct me
BUDGERIGAR GENETICS MADE SIMPLE
Dominant and Recessive
If you were to pair a pure green budgie with a pure blue budgie, all of the babies will be green, but will carry a blue hidden gene that will not visually be there... Why? Because green is the DOMINANT colour and blue is RECESSIVE, so the blue is hiding but a green budgie is all you can see on its feathers. Another way to rephrase this is that green is somehow stronger than blue, and blue is weak, so green wins and is visually there. All mutations are either Dominant or recessive, but some mutations are sex-linked. For example, a spangle gene is dominant whilst recessive pied gene is recessive
Split budgies
Like above, as i said, all the babies are green with the hidden blue in the. In breeders terminology, these budgies are "green split blue" or represented as green/blue. The first colour or mutations on the left side of the bracket (green) is the colour you can visually see, but the variety or colour after the slash (blue) is the colour you cant see but its there. Another example is a Light green/ cinnanom... can you guess which is dominant and which isn't?
There are few outcome which are impossible to occur, such as a green/ dominant pied. In this pairing, both are dominant so a dominant cant be split for dominant, only recessive. It is also important to remember in no circumstances can a recessive be split for dominant...impossible.
Single factor and Double Factor
Budgies have two genes giving us colours. Lets say we have a yellow face budgie sitting here :yellowhead: (yellowface is dominant) If only one of the two budgie colour genes had yellowface in it, (aka Yellowface type 1) the budgie will display more of a cream face, and if both of the genes had yellowface in them (aka Yellowface type 2) the budgie will display a bright yellow face and will be more likely to turn the blue feathers on them green (the yellow "bleeding" throgh the blue or mixing).
Same with dominant pied, if one gene had dominant pied in it, ( aka single factor dominant pied) the budgie will have just the usual band across the tummy and half ground coloured wings but double factor dominant pieds, with both gene with the pied in them will seem and look more like a recessive pied, but lacking the full black eyes.
Sex-linked Budgies
Some mutations are sex-linked, and they are Opaline, Cinnanomwing, Lutino, Albino and Lacewing. Remember how i said that budgies two chromosomes? Well, hens cannot be split for these mutations that i mentioned before, as these mutations are linked to the male producing cells.
So, there are only five possible ways of having these mutations in a bird... lets use Lutino as an example. there are no other ways of having these mutations in a bird.
1 Lutino cock- Lutino factor visible
2Split Lutino cock- lutino factor is hidden and cannot be seen
3 Non Lutino cock- has no Lutino factor at all
4 Lutino he- Factor visible
Non Lutino Hen- Has no Lutino factor at all.
So, those five mutations i mentioned above a hen has or hasnt got and cant be split for any of them. Why is it like this.. Well this part is quiet confusing but i will try and put it straight, you just need to know before you read this that a cock has two X chromosomes and a hen has one X and one Y : A cock has two X chromosomes, and a Lutino hen has one. For a cock to be a visual Lutino, It must have lutino factor in BOTH it chromosomes. For a hen to be a visual Lutino, she only has to have its X chromosome and only that one to be a visual Lutino. if a cock had only one of its two X chromosomes with the Lutino factor, then he is split for Lutino, on the otherhand because hens have only one X chromosome they cannot be split for this Lutino factor. The Y chromosome in hens cannot carry Lutino or any other of the five mutations.
Dark Factor... almost there!
Dark factor is another way of saying a budgie has two genes. Ifi have a light green budgie, :grbud: , he has no dark factor in either of these two genes. If i got one of the genes and put dark factor in it, then the bird is a dark green. but if i get BOTH of the two genes and add dark factor to both then i get an olive budgie. So light to dark: light green, dark green, then olive. the same applies to Blues: skyblue, cobalt, then mauve.
This is simple genetics and i hope you will undestand how your little came to be the colour he is now
:hug:
Daniela
References: The complete book of Budgerigars by John Scoble and the internet and this lovely forum.