Dilute Budgerigar Mutation - Genetics

Genetics

The Dilute mutation is recessive to its wild-type allele, so a bird possessing a single Dilute allele (the heterozygote) is identical in appearance to the wild-type Light Green. That is, the presence of a single wild-type allele is sufficient to permit the production of the normal number of melanin granules. Among the budgerigar fancy such a bird is said to be a Light Green split dilute, usually written Light Green/dilute, although Light Green/yellow has been used.

In a bird which has two Dilute alleles (the homozygote) the number of melanin granules is greatly reduced, to around 5% of the normal amount. This results in a much reduced intensity of the black markings, and less absorption of light which passes through the cloudy layer in the medulla of barbs. As this absorption of light is a necessary part of the process which generates the blue colouration the intensity of blue is also greatly reduced.

The Dilute mutation is one of a series of multiple alleles at the same locus, called dil+ in the wild-type. The others are the Clearwing (dilcw) and Greywing (dilgw) mutations. The Dilute allele (dild) is recessive to all other alleles at this locus, so for the Dilute character to be expressed in the phenotype the genotype must be homozygous for this allele.

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