Split simply means a hidden mutation and not visual. One person can't see a 'split' mutation until a breeding proves it.
There are 2 kinds of 'split' mutation :
1. Recessive genes - usually a budgie is split for recessive genes due to only one gene present and hence this recessive gene can't show visually. In order to show a recessive gene, each of this said gene must be passed from the hen and also the ****. Otherwise, the budgie would be split for this recessive gene.
Examples of recessive genes are greywings, dilutes, recessive pieds, fallows, blue series budgie (blue is recessive over green series budgie), texas clearbody.
2. Sex-linked mutations - this occurs in males only and not hens. A **** can be split for a sex-linked mutation and not a hen which must be visual.
Examples of sex-linked mutations are albinos, lutinos, lacewings, cinnamons, opalines.
It must be pointed out that dominant mutations cannot be split. As the word 'dominant' suggested, a budgie with a dominant mutation usually produce 50% offspings of similar dominant mutation.
Examples of dominant mutations are spangles, clearflights, dominant pieds, clearwings.
Is this simple enough or you get more confusion ? Please let me know, OKAY.
Think of it like the genetics equations that you have probably done in a science class while talking about Mendel's peas. Lol.
Each parent passes a gene on to a chick in the DNA that they give them. Depending on the DNA combinations, you get different mutations. For example. A hen that is blue has two recessive genes, or else she would be a green, since green is dominant over blue. If blue =b and green =B, than that hen would be "bb". A hen that is green would EITHER have two dominant genes "BB" or one dominant and one recessive "Bb" That hen would be split for blue. You wouldn't see it, since the green B would hide it, but if you bred her to a **** that was either "bb" or "Bb" you would get "bb" or blue babies.
Since the dominant hides the recessive, you won't be able to tell if the bird is hiding a recessive unless you either know the parentage or you breed the bird and the offspring show the recessive trait.
Using Roland's #2 example
Greywing X Normal= All normal
One parent is showing the recessive Greywing (gg) and the other in this particular case is GG, rather than Gg. So the babies would all be Gg, and be split for Greywing. If the other parent was Gg, then the babies would be a combination of Gg (Normal) and gg (greywing).
In the example for #3, both parents are split for Greywing ("Gg" and hiding it), since it appeared in the chicks. Chicks would be a combination of GG (25%), Gg (50%), and gg (25%). That is just looking at the Greywing expression possibilities, not the others.
Does this make sense?
Also, some mutations are sex linked. For example, a calico or tortoise-shell cat is almost always female. Very, very rarely will a cat that has this coat pattern be a male. Or in humans, hemophilia is found much more often in males than in females. Certain traits are sex linked, and so only certain genders will be able to express better than the other one would. This post explains it better than I could: http://talkbudgies.com/showthread.php?t=35805
I love reading through it. It does a great job of explaining the various mutations, what to look for to identify them, and which traits are dominant and which are recessive. Or which ones can show together, leading to that really long description that we see with some birds. Lol.
Lindsey also has a great interactive guide on her website. You can look at the mutations, and then click on a link that will take you to a chart that will clearly show breeding outcomes. It is under construction though, FYI.
Just remember. Dominant can never hide. So you always have 3 options. Completely Dominant showing the Dominant Trait, Dominant/Recessive, which will always show Dominant but be SPLIT for the Recessive trait and able to pass it along to the offspring if the other parent is carrying the trait, and Completely Recessive, which will always show the Recessive trait.
I hope this helps. There are other factors of genetics that I didn't get into here, but hopefully this helps with the basics. I love doing Mendol's exercises, or Punnett Squares as they are usually called. Can be pretty complicated sometimes when you have traits that are linked together. If you want to know more, check out this website: