Dark and Blue linkage rate in IRN
Posted: Thu Mar 12, 2015 12:40 pm
Hi everybody,
It is commonly accepted that the gene location (loci) in the chromossomes is roughly conserved among species, specially inside the same familly (parrots for us), so that results obtained in one species can be extrapolated to others.
Budgie is the parrot species with a higher reproduction rate, higher number of identified mutations and longer breeding history and, thus, most of results about gene location and linkage rates come from budgi studies. We are currently accepting such results as the theoretic frame of our breeding planing, without further questioning.
Here I want to analyze what we really know:
About budgies: http://en.wikipedia.org/wiki/Dark_budgerigar_mutation
"The loci of the Dark mutation and the Blue allelic series are situated on the same autosome, so the Dark mutation is linked to the Blue allelic series. The cross-over value (COV) or recombination frequency between the Dark and Blue loci is often stated to be about 14%, but several careful measurements of this COV show quite widely varying results. Early measurements by Duncker and independently by Steiner obtained values of 14% and 7.6% respectively, and T G Taylor and C Warner collected results which showed only 5 cross-overs in 140 - a COV of 3.6% . Included in these were results from T G Taylor's own experiments, in which he found no cross-overs in 86 birds bred. It is now known that the environment and other genes can influence the COV, so some variability should be expected. A reasonable average of these measurements is a COV of 8%."
Some questions:
1. Why should we accept a COV of 14% for IRN if the detected values in budgies show such a wide range (0-14%)?
2. Is it logical to accept that the COV in one species can change depending on the presence of other mutations or on environemental factors, and at the same time to accept that the COV is "fixed" among species?
3. Do we have any prove that the known IRN blue locus and the Budgie blue locus are one and the same? The behaviour of homozygous parblues in both species is different and, thus, we should think that we are facing different blue loci ... showing different linkage rates with Dark.
The best experiment to prove or disprove that both Blue mutations in IRN and Budgies are/not the same would be to hybridaze a Blue IRN x Blue Budgie.... but it is not possible. Do you know any psittacula species able to hybridaze with IRN, and showing an homozygous parblue bluer than the heterozygous ParblueBlue (like Budgies)?
Has anybody breeding cobalts and Dark greens found some "strange" offspring results?
Regards
Recio
It is commonly accepted that the gene location (loci) in the chromossomes is roughly conserved among species, specially inside the same familly (parrots for us), so that results obtained in one species can be extrapolated to others.
Budgie is the parrot species with a higher reproduction rate, higher number of identified mutations and longer breeding history and, thus, most of results about gene location and linkage rates come from budgi studies. We are currently accepting such results as the theoretic frame of our breeding planing, without further questioning.
Here I want to analyze what we really know:
About budgies: http://en.wikipedia.org/wiki/Dark_budgerigar_mutation
"The loci of the Dark mutation and the Blue allelic series are situated on the same autosome, so the Dark mutation is linked to the Blue allelic series. The cross-over value (COV) or recombination frequency between the Dark and Blue loci is often stated to be about 14%, but several careful measurements of this COV show quite widely varying results. Early measurements by Duncker and independently by Steiner obtained values of 14% and 7.6% respectively, and T G Taylor and C Warner collected results which showed only 5 cross-overs in 140 - a COV of 3.6% . Included in these were results from T G Taylor's own experiments, in which he found no cross-overs in 86 birds bred. It is now known that the environment and other genes can influence the COV, so some variability should be expected. A reasonable average of these measurements is a COV of 8%."
Some questions:
1. Why should we accept a COV of 14% for IRN if the detected values in budgies show such a wide range (0-14%)?
2. Is it logical to accept that the COV in one species can change depending on the presence of other mutations or on environemental factors, and at the same time to accept that the COV is "fixed" among species?
3. Do we have any prove that the known IRN blue locus and the Budgie blue locus are one and the same? The behaviour of homozygous parblues in both species is different and, thus, we should think that we are facing different blue loci ... showing different linkage rates with Dark.
The best experiment to prove or disprove that both Blue mutations in IRN and Budgies are/not the same would be to hybridaze a Blue IRN x Blue Budgie.... but it is not possible. Do you know any psittacula species able to hybridaze with IRN, and showing an homozygous parblue bluer than the heterozygous ParblueBlue (like Budgies)?
Has anybody breeding cobalts and Dark greens found some "strange" offspring results?
Regards
Recio