Genetic Recombination Sex-linkage

[TomDeGraaff]

The reason I started this thread was to deal with recombination in finches. However, I need information on what sex-linked mutations are around in finches. I'll review this thread and see if I can list the ones we have so far.

The discussion of lacewings etc is very relevant to the idea of recombination. Firstly, the most common example of recombination appears to be between opaline and ino mutations in parrots. Are there opaline mutations in finches? Do they inherit the same (sex-linked) as parrots?

If two sex-linked mutations become visible on the same bird, then it is possible (probable) that recombination has occurred. That's what I am interested in discovering in finches.

I suppose so far we have been discussing what sex-linked mutations are out there and now I wonder if any of them, particularly in zebbies or canaries, are the result of two sex-linked mutations recombining to produce a new colour eg fawn (cinnamon) marked white zebras.

[Alf63]

After 30 years breeding parrot (excluding budgies) & some finch mutations I will have ago at the risk of being shot down.

Autosomal Recessive Cock or Hen mated to Normal - All young (Hens & Cocks) are split

Sex-linked Recessive Cock mated to Normal Hen - Split Cocks, Mutation Hens. (All young can be sexed by colour)

Sex-linked Recessive Hen mated to Normal Cock - Split cocks & Normal Hens

I will add from my experience that genetic crossover isn't that common in the mutations I have bred over the years. The majority of birds exhibiting multiple colours are a result of pairings of mutation hens with cocks split for multiple colours ie. Cinnamon Red Black Eastern Rosella (Cinnamon [SLR] Opaline [SLR] Melanistic [AR]). This leads to large range of possible outcomes in both cocks & hens but shouldn't be confused with cross over.

Alf63

[TomDeGraaff]

Thanks Alf. Those three pairings are worth noting. Espe ially the middle one. Sexing young in the nest is VERY useful!

[TomDeGraaff]

Getting back to Red's canary examples, the Isabel is a combination of agate and cinnamon.

If both those mutations are sex-linked, then isabel reulted from recombination, I assume.
Does isabel inherit as its own, independant sex-linked mutation?

[Red]

Why are we talking about budgie and cockateil mutations on here,especially lacewings,i don't think it is applicable to finches but i do understand that most mutations run the same line in most birds but it's hard to understand if you don't use a finch as an example.

OK the classic recombination example in canaries for sex linked varieties is the isabel which is a combination of cinnamon and agate. I have tried to keep it simple. Let me know if I have got anything wrong. It is a bit trickier than simply breeding the two varieties together and here's why.

1. If you cross a cinnamon male to an agate female all the young females will be cinnamon and not carry agate. In the reverse cross (agate male) the female offspring will be agate but won't carry cinnamon. This is because a female bird always inherits a sex linked trait from her father.

2. The males from either of the above pairings will appear to be a normal green canary but they do carry both cinnamon and agate. These males inherited cinnamon from one parent and agate from the other. Male canaries must have two doses of a sex linked trait for it to be visible. Males that have just one dose such as the offspring in this example are known as "splits" or "carriers".

3. Regardless of what they are bred to, the agate and cinnamon carrier males will produce female offspring that are either cinnamon or agate. This is because the female offspring inherits either the chromosome (chunk of DNA) that carries the cinnamon gene or the chromosome that carries his agate gene. It should be impossible for any offspring to receive both cinnamon and agate because the male has them on different chromosomes, only one of which he can pass on.

This is where meiosis and crossing over events come in.

An bird inherits one set of chromosomes from it's mother and one from it's father. Meiosis is the process where a birds two sets are divided into one set that can be used in a sperm or egg.

An event called "crossing over" sometimes happens in meiosis where pairs of chromosomes swap pieces with each other. When it happens to our agate and cinnamon carrier males, a sperm carrying both agate and cinnamon may be produced. If any of these sperm with recombined chromosomes fertilises an egg, a composite cinnamon agate hen (called isabel) might be produced. This is rare and you are better off putting your effort into buying an isabel canary than breeding the numbers required produce one from cinnamon and agate carrier males.

Red

[TomDeGraaff]

I wonder about the cream-backed zebras.
Could they be a fawn / marked-white or fawn / chestnut-flanked recombination?

[Red]

Does isabel inherit as its own, independant sex-linked mutation?

Yes mostly. Some cross isabel back to agate every three or so generations but this is for show points and not because it is strictly necessary genetically.

There is always the chance of another crossing over event separating the two traits. I know budgerigar breeders can have the odd ino bird turn up in lacewing pairs.

Sorry can't help you with zebs.

[TomDeGraaff]

"If you consider canaries finches:

Ivory or Rose
Cinnamon
Agate
Pastel
Satinette

An isabel canary is a cinnamon agate"

Hey Red.
Do you have any knowledge of any other combo's such as pastel with any of the others? (pastelagate?)

[Red]

Hey Red.
Do you have any knowledge of any other combo's such as pastel with any of the others? (pastelagate?)

Of course you can have agate pastel, rose agate, rose isabel, rose isabel pastel and so on.

The more difficult to produce colours are popular with those seeking a challenge. The most difficult combo I know of is called the "pearl" an isabel satinette lizard (lizard is not sex linked). A few examples have been produced but the markings on the ones I have seen have been so faint that I would not bother.

[TomDeGraaff]

I gather these other combos such as isabel satinette inherit as their own sex-linked mutation (?)