A number of DNA labs are advertising a test for the Lavender gene in chickens. I believe these tests are unreliable and not worth using. I am willing to have my mind changed, if any lab wishes to work with me to validate their DNA tests. I actually did work with one lab to validate their test for the lavender gene and they failed that completely. The test I worked with them on was worse than useless. A “useless” test would give no result if it could not be certain of the results. This test will give the wrong result – consistently. I recommended they not bring the test to market because it was not useful to chicken breeders working with the lavender gene. They decided to sell the test anyway because they had invested so much in developing the test. Several other labs are following suite. I have no knowledge of how those labs have validated their tests, but given the low budgets these small labs have, I suspect they have done no validation at all.
This opinion came out of my work with a genetic testing lab. They were testing their lavender gene genetic test, so I sent samples from all my breeds that were lavender or known heterozygous for lavender. The results were unexpected.
All of the lavender large fowl (Ameraucanas, Marans, Opal Legbars) tested negative for the lavender gene! These were birds that were obviously lavender from their phenotype and their genes proven to be single gene recessives (a cross to non-lavender resulted in all non-lavender chicks, but the F2’s produced 25% lavender phenotypes).
All of the lavender bantams (Ameraucanas and Cochins) tested positive for the lavender gene, as expected.
The explanation from the lab’s geneticist was that my large fowl breeds must look lavender as the result of a different gene and so these birds are not really lavender genetically. There is a gene discovered by some Chinese researchers that produce a color they called “grey”. The lab thought that was the most likely explanation. My theory is that there are 2 different alleles that dilute color for the same gene. Determining whether this second lavender is a second allele or a different gene is rather easy. I explained my plan to the geneticist and got agreement about how to test the competing theories.
To determine if there are in fact 2 separate lavenders (genes or alleles), I crossed a (male) lavender cochin (they DNA test positive for lavender) and a (female) opal legbar (they DNA test negative for lavender). The resulting chicks were all lavender phenotypes. If there were 2 separate genes involved (as the testing lab concluded), then all should have been black phenotypes. There are 2 possibilities to explain this (that I have thought of):
- There are 2 separate genes, but the effect of the non-black alleles are additive, so that if at least 2 of the 4 alleles involved with the 2 genes are non-black, then the phenotype is non-black (lavender).
- There is only 1 gene involved, but 3 possible alleles, instead of the 2 previously known. One of the alleles is “black” (no dilution) and is dominant over both other alleles, which are distinct in their base pair sequences, but have the same dilution effect, so that either of these alleles can produce a lavender phenotype, as long as no black allele is present in the gene.
The next test was to evaluate F2 chicks. If there are 2 separate genes involved that operate independently, then the F2’s should segregate such that approximately 5/9 of the chicks should be black. If anyone wants to understand how I came up with that, message me and I will show my work. If there is only 1 gene involved, and 3 alleles for the lavender locus, then no chicks will be black, as both parents are non-black at the gene. After hatching over 100 F2 chicks with NO non-lavender phenotypes presenting, I am now convinced there there is a 3rd allele on the gene that we attribute to “lavender”. I believe the 3 alleles are:
- No dilution – this is dominant and results in a phenotype with no dilution. This is the normal or “wild type” for the gene
- Lavender #1 – this is a recessive gene that dilutes the phenotype if none of the 1st allele are present. This is what the DNA test is detecting
- Lavender #2 – this is a recessive gene that also dilutes the phenotype if none of the 1st allele are present. This is not detected by the DNA test and shows as negative for lavender, the same as the 1st allele.
The lavender test developed by this DNA lab is testing for the presence of “Lavender #1” and if it does not find it, presumes the phenotype to be non-dilute. This makes the test nearly useless for most poultry breeders working with lavender, as “Lavender #2” seems to be very common, probably more common than #1. If instead, they tested for the number of genes with the “no dilution” allele, then they would have a viable test. Even better, if they could detect all 3 alleles and report the state of the gene based on the number of each allele, the test would be very useful, as there are detrimental effects from the lavender gene that might be linked with only 1 of the alleles.