Victorian Zebra Finch
Sequencing of the Zebra Finch. By G. PASCOE
Since early 2010 a number of scientific study groups around the world have Sequenced the genome of the ZEBRA, along with a lot of other birds, i.e., they have counted all the chromosomes and all of the gene loci contained in them.
The one that stands out is there is no X, Y. Sex controlling Chromosomes, as previously thought, the sex controlling chromosomes are Z,W.
The Homogametic version is Z, Z = Male, The Heterogametic version is Z, W = Female
There are twice as many genes on the Z chromosome than the W chromosome. The mode of inheritance for recessive sex linkage and dominant sex linkage, still works the same, but there is a sex bias towards producing more males than females.
I have for 4 years now used the results of another study from USA, the study was about the selection of mates in birds, they found that the zebra hen has a preference for the best coloured males and the strongest, My records show that of 620 young produced, Having fitted a red ring to the cocks and a black ring to all the hens more young per pair produced, and 70% of them were hens, unlike the normal, more cocks than hens.
Another thing to come out of this is 6 young per nest is not conducive to producing the best birds out of the nest because of the competition in the nest for food, the young are only average for a long period after flying, this makes them much older before you can select for the points you are working for. One way to over come this is to foster out eggs & young and only leave 3 young in a nest, you will see the results quicker and be able to plan the next three generations earlier.
This Z, W chromosome sex determining system is used by all birds, all egg laying fish and all egg laying reptiles. One of the reasons for this is the number of young produced per female, unlike the mammalian X,Y where in most cases only one young per female, and a long time spent on rearing, the egg layers do it in numbers, the predation of male birds can be high as well.
Most Female birds are not monogamous, they will mate with any male that fits their criteria, DNA testing has proven that nests full of young do not all have the same father, when multiple pairs are house in the same aviary.
All the gene loci on all the chromosomes including the autosomal and Z, W, represent 100s of thousands of genes. The problem as I see it is most people I have talked to are only concerned about mutations that change, size and colour.
We now know that of these total number of genes, 65% of the genes (a very large number) are working towards, immune response, this means they are working on manufacturing bacteria or fighting bacteria, that is being picked up by the host.
What if these genes mutated? Have they already? Have we got diseases today that were not about years ago? If they do mutate how will we know?
More work to be done I venture.
One study group working on the Zebra genome found that the birds they used had different origins 3 birds came from SWEDEN, 7 birds came from USA, and the rest from Australia.
DNA Tests showed that a number of CLASS 1 genes and a number of CLASS 2 genes showed variations in gene numbers in MHC= Major Histocompatibility Complex= these genes are working in immune response,
There was also a large shift in RFLP = Restriction Fragment Length Polymorphism.
The birds from Sweden had a RFLP as high as 27 changes in class 2 genes.
The rest of the birds only had levels between 12 and 20 RFLP
The conclusion to this is the Swedish birds are a new or different variety or sub species,
This is the Darwin theory at work, the birds gene pool changing to their environment.
by G. Pascoe