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Discussion Starter · #1 · (Edited)
I know it's a rare genetic defect where two zygotes fuse, but could you still get a blue and green half sider if the green parent was homozygous green? All the normal babies would never be blue, just split for blue, but could a half sider have blue on one side anyways, or is it impossible? :S

EDIT: If you scroll down, you'll see that I later explain the mutation in great detail.
 

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A half sider is not a real mutation. It is just two birds that were formed together. You cloud have a half sider, and not know it, if all of your chicks were the same colour.
 

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Discussion Starter · #4 ·
A half sider is not a real mutation. It is just two birds that were formed together. You cloud have a half sider, and not know it, if all of your chicks were the same colour.
I know it's not a real mutation, but if your birds just happened to have a half sider chick, are the two eggs that fuse already fertilized or not? If the parents were a blue and a green bird, would it matter if the green one wasn't split for blue, or would it have to be split in order for one side to be blue?
 

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Discussion Starter · #5 ·
Anything is posiable in Mother Nature
I don't think so though... A lot of things in nature work together according to rules/laws of nature, even exceptions have rules that pertain to them. I'm wondering what rules apply to the exception that is the half-sider.
 

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Discussion Starter · #6 · (Edited)
Well I have figured out how half siders work and I may as well post it here just in case anyone stumbles onto this thread and wants to know. So a half sider is a tetragametic chimera (a form of congenital chimerism); 'tetra' meaning 4, 'gametic' meaning gametes (sperm and ova) and 'chimera' meaning a single organism composed of two different populations of genetically distinct cells that came from two different zygotes. Four gametes come together (2 sperm and 2 eggs; (first the each sperm fertilize a separate egg, then the eggs fuse together), so it would kind of look like reverse meiosis) to create a completely unique budgie.

Half siders are like the opposite of identical twins, instead of a single zygote splitting into two identical zygotes, it's two different zygotes fusing into one! Just to be clear, a zygote is the initial cell formed when two gametes join.

It happens purely by accident and is not genetic. In birds it obviously occurs in the zygote or blastocyst stage of development before the egg shell forms around the chick. (There are five main stages of development: zygote, morula, blastocyst, embryo, and fetus). It generally occurs when the female has released two eggs from her ovary at the same time by accident and they fuse for unknown reasons after each is separately fertilized by different sperm.

Because the half sider is the combination of two baby budgies fused together, it essentially has two different sets of DNA, so the chick can come to possess organs and body parts that have different sets of chromosomes. For example, in a visual half sider, pigment on one side/part of the body is controlled by one set of chromosomes while pigment on the other side/part of the body is controlled by the other set of chromosomes from the other zygote, which is why half siders are generally two colours (of course they could also be the result of a fusion of two green, (for example), budgie zygotes which would result in a normal-looking green budgie even though it's really a half sider). If the zygotes had not fused, you would have gotten two healthy, perfectly normal budgies (one blue one and one green one). Half siders could also be half albino, half blue or half lutino, half green! It all depends on the parents.

So to answer my own question, no, you can't get a classic half sider from a blue parent and a green parent if the green parent is homozygous green; it would have to be split for blue in order to get a blue and green half sider. If it were homozygous green no blue offspring would ever arise so any zygotes that fused would always ever be green zygotes, no blue ones.

When it comes to breeding a half sider with another budgie it all depends on if the reproductive tract of the half sider was formed from one set of chromosomes or from both sets. If from one set, the half sider can create either Bb gametes or bb gametes if it's a standard blue and green half sider, giving you a normal chance for offspring. If from both sets, it can create Bb and bb gametes, giving you 3x the chance of getting blue offspring from a standard blue and green half sider. But if the gender of one zygote was female and the gender of the other was male when the half sider was formed, there's a chance your half sider budgie is infertile due to a number of reasons including malformed genitalia and hermaphroditism. Hermaphrodite half siders may have two colours to their cere, one side blue, the other side brown.

I don't know if it's possible for 3 or 4 zygotes to fuse together and survive but you never know!

Phewf! I think that's everything you need to know about half siders and how they come to be! :budgie:
 

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Sorry if it seems like I'm hijacking the thread but I don't completely understand 'half' sided budgies. I've posted this picture a while back of one of my budgies and was wondering if this budgie was considered to be a a half-sider?



If the picture isn't good enough i'll try to get a better one tomorrow.
 

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Discussion Starter · #8 ·
Sorry if it seems like I'm hijacking the thread but I don't completely understand 'half' sided budgies. I've posted this picture a while back of one of my budgies and was wondering if this budgie was considered to be a a half-sider?
If the picture isn't good enough i'll try to get a better one tomorrow.
It's no problem at all, your budgie isn't a half sider, it's a double factor yellow face type II. Usually half siders are split vertically down the middle instead of horizontally. Yellow face budgies are a combination of two types of blue. Since blue is actually produced by a defective yellow-making enzyme, when you have two different types of blue (the other type is called "par-blue"), they are found at different loci on the gene so they compensate for each other's defects, and a little bit of yellow pigment is produced. That's why your budgie has a yellow face instead of a white face. With a double factor yellow face type II, the yellow only moves down to the chest, while with a single factor yellow face type II, the yellow covers the whole body, giving you a sea green budgie. If you bred you budgie to a normal blue budgie, all the offspring would be single factor yellow face type II (yellow faces and sea green bodies)! :) I hope I helped!
 

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A true half-sider looks like two halves glued together for lack of a better explanation.
There is nothing we can do to try to breed one. It only happens when nature takes charge.

Exactly like Kat shows. Beautiful isn't it.
 

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Sorry if it seems like I'm hijacking the thread but I don't completely understand 'half' sided budgies. I've posted this picture a while back of one of my budgies and was wondering if this budgie was considered to be a a half-sider?



If the picture isn't good enough i'll try to get a better one tomorrow.
Half siders are literally left half and right half being different.

Your budgie is beautiful.
 
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So half siders are extremely rare then?

Those two budgies are amazing, stunning, beautiful! i have never seen anything like it before, they must be worth an absolute fortune in the budgie world..

I just... I am just in awe. Wow.
 

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Discussion Starter · #14 ·
Half siders are literally left half and right half being different.
Well it all depends on how the zygotes fuse. Generally it's vertically half and half down the middle, but sometimes it's not so perfectly divided. Here are a couple of examples of that:
 

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Discussion Starter · #15 ·
So half siders are extremely rare then?

Those two budgies are amazing, stunning, beautiful! i have never seen anything like it before, they must be worth an absolute fortune in the budgie world..

I just... I am just in awe. Wow.
They are pretty rare, at least the visual ones are. There are probably many half siders people don't know about because they are the fusion of two white base or two yellow base zygotes so the resulting bird it just one colour. :)
 
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