My Pigeon Journal article

General discussion about pigeon genetics
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AdamArcher
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My Pigeon Journal article

Post by AdamArcher »

Here is a copy of a letter/article I wrote for the Australian Racing Pigeon Journal.

I was pleased to see the article by Allen Limeburner in the recent Pigeon Journal - as the owner of pigeongenetics.com I'm very happy to see people basing their breeding on proven genetics and science rather than age old theories and superstitions.

I would just like to offer two clarifications though.

The first is quite minor - pigeons use the ZW sex-determination system rather than the XY sex-determination system that humans use. This means that a cockbird carries two Z chromozomes, and a hen carries ZW. The opposite is found in humans, where males have the two different sex chromosomes (XY) and females have the two X chromosomes. Pigeons do not have X or Y chromosomes.

The second is in relation to how the sex chromosomes are passed onto the bird's offspring. Allen's article implies that a cockbird passes on a complete copy of one of his Z chromosomes to his children, and this is not the case. It isn't possible for a cockbird to have a "good" and a "bad" Z chromosome, and a toss of the coin to decide which one a young bird inherits. Imagining it working in this fashion forgets the important steps of "meiosis", "crossover", and "recombination".

Basically, this means that while a cockbird does indeed have two Z chromosomes, he does not pass on a complete copy of one of them to each child. Rather, both chromosomes are split at some point along their length, and stitched (or "recombined") with the matching part of the opposite Z chromosome, and an entirely new Z chromosome is created for the new life. Genes from both of the father's Z chromosomes are now found on the new Z chromosome that is passed onto the next generation (this is called "crossover", as genes that were originally on different Z chromosomes are now found on the same one, having "crossed over" to the other side).

Hens, on the other hand, do pass on their complete Z chromosome to their sons (as they do not have another Z chromosome to perform meiosis with), and they pass on their complete W chromosome to their daughters. It is important to remember, though, that the hen's Z chromosome is unique to her, it is not a copy of one of her father's, and that chromosome will go through the same meiosis process when the son breeds in the future.

Hens also pass on their (almost entirely unmutated) mitochondrial line to all their young - and some have theorised that this may be a shortcut to recreating champions from a good hen, though recent published research has shed doubt on this (see, "The myth of mitochondrial DNA and race performance in racing pigeons" - Kolvenbag and Scott, 2021).

As I said, I'm very happy to see people taking the science of genetics into account when planning matings. Genetics isn't a scary science, and just a basic knowledge of how it works can only ever help a pigeon breeder. There are a huge amount of resources freely available online and in print to help a breeder grasp a basic understanding of pigeon genetics.
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HomeSweetHome
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Re: My Pigeon Journal article

Post by HomeSweetHome »

Great job Adam!!
Norcropper
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Re: My Pigeon Journal article

Post by Norcropper »

So, you are saying that a crossover occurs on the z chromosome every time a sperm is created?
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AdamArcher
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Re: My Pigeon Journal article

Post by AdamArcher »

Not just the cock's Z, all the chromosomes apart from the hen's W.
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