Sex-linked Clearbody budgerigar mutation

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The Sex-linked (SL) Clearbody budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Texas Clearbody variety.

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Over the years many mutations have been reported which produce a (relatively) clear yellow or white body with normal black or dark wing markings, approximating to the beautiful painting of a (hypothetical) "laced Yellow" by R A Vowles shown in Dr M D S Armour's book, "Exhibition Budgerigars". [1] In an article published in Cage and Aviary Birds [2] Dr T Daniels summarised those that were known in 1981. Many of these failed to become established, and others, reported separately, may have been the same mutation which appeared in different parts of the world. The Sex-linked Clearbody was one which was established successfully in the US.

Appearance

In the green series the Sex-linked (Texas) Clearbody has a yellow body with a pale greenish cast, and white in the blue series with a pale bluish cast. [3] The cast is palest on the breast, increasing towards the vent and rump. The variety has normal wing marking in grey-black, off-white to grey flights, a tail rather lighter than usual, and normal violet cheek patches. The appearance is rather similar to the Dominant (Easley) Clearbody, but the normally coloured cheek patches distinguish the Sex-linked (Texas) Clearbody. For photographs of Sex-linked Clearbodies, see.

Historical notes

The details of the first appearance of the SL (Texas) Clearbody have been lost, but the Clearbodies being bred by Floyd Guelker in 1958 were probably of this type. The original mutation is thought to have originated in a colony aviary in Texas around 1955. [2] In 1958 Gay Terraneo of Wilmington and Mr John Papin of Long Beach, both in California, obtained respectively a pair and a hen, and showed that the mutation is a sex-linked recessive.

Jeff Attwood brought the variety to Britain in 1989. [4]

Genetics

The Sex-linked Clearbody mutation is sex-linked and recessive to wild-type. It is a further mutation of the ino locus with the symbol inocl. Together with the Ino mutation, it forms a series of multiple alleles. The order of dominance is ino+, inocl, ino, with ino being the most recessive. Mutations which are allelic to Ino and cause partial albinism are known as Par-ino mutations in parrot species. [5]

SexGenotypePhenotype
Cocksino+/ino+Normal
ino+/inoclNormal (/SL clearbody)
inocl/inoclSL Clearbody
ino+/inoNormal (/ino)
inocl/inoSL Clearbody (/ino)
ino/inoIno
Hensino+/YNormal
inocl/YSL Clearbody
ino/YIno

The sex determination system used in birds is the ZW system. In this system, cock birds have two Z chromosomes, and hens have one Z and one W. So in hens whichever allele is present on the single Z chromosome is fully expressed in the phenotype. Hens cannot be split for Sex-linked Clearbody (or any other sex-linked mutation). In cocks, because Sex-linked Clearbody is recessive to wild-type and dominant to Ino, the Sex-linked Clearbody allele must be present on both Z chromosomes (homozygous) or present on one with an Ino allele on the other to be expressed in the phenotype.

Cocks which are heterozygous for Sex-linked Clearbody with the wild-type allele are identical to the corresponding Normal. Such birds are said to be split for Sex-linked Clearbody, usually written '/SL Clearbody' or '/Texas Clearbody'.

Cocks which are heterozygous for Sex-linked Clearbody with the Ino allele are visually similar to homozygous Clearbodies, although possibly with clearer bodies. [6] Such birds are said to be split for Ino, usually written 'SL Clearbody/ino' or 'Texas Clearbody/ino'.

The table on the right shows the appearance of all possible genetic combinations involving the Sex-linked Clearbody and the Ino mutations. [5]

As the ino locus is on the Z-chromosome the Sex-linked Clearbody gene is linked to all other sex-linked mutations, including Opaline, Slate, and Cinnamon. Because Sex-linked Clearbody is an allele of Ino, the cross-over values between Sex-linked Clearbody and other sex-linked mutations are identical to those between Ino and those mutations. For these cross-over values, see the Genetics section in the Ino budgerigar mutation article.

Notes

  1. ↑ Armour, M D S, Exhibition Budgerigars, Cage Birds, p. 88
  2. 1 2 Daniels, T (18 July 1981), "The Laced Clear mutations - a mixed bag", Cage and Aviary Birds (29): 3–4
  3. ↑ Hesford, C, The Texas Clearbody Budgerigar, archived from the original on 2008-01-05
  4. ↑ Al-Nasser, G, Rare Budgerigar Varieties, the Clearbody
  5. 1 2 Hesford, C, The Par-ino Varieties, archived from the original on 2008-01-05
  6. ↑ Onsman, I, Genotypic and Phenotypic Aspects of the Sex-Linked clearbody, archived from the original on 1999-10-03

Related Research Articles

Dominance (genetics) One gene variant masking the effect of another in the other copy of the gene

In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes (autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child. Since there is only one copy of the Y chromosome, Y-linked traits cannot be dominant nor recessive. Additionally, there are other forms of dominance such as incomplete dominance, in which a gene variant has a partial effect compared to when it is present on both chromosomes, and co-dominance, in which different variants on each chromosome both show their associated traits.

Budgerigar colour genetics

The science of budgerigar color genetics deals with the heredity of mutations which cause color variation in the feathers of the species known scientifically as Melopsittacus undulatus. Birds of this species are commonly known by the terms 'budgerigar', or informally just 'budgie'.

The Recessive Pied budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Danish Pied variety, aka Harlequin. It is believed by Inte Onsman of MUTAVI to be the same mutation as the Anti-dimorphic Pied found in some parrots. The Dark-eyed Clear variety results when the Recessive Pied and Clearflight Pied characters are combined.

The Dark budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is part of the genetic constitution of the following recognised varieties: Dark Green and Olive in the green series and Cobalt, Mauve and Violet in the blue series.

The Yellowface I budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars.

The Yellowface II budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. In combination with the Blue, Opaline and Clearwing mutations, the single factor Yellowface II mutation produces the variety called Rainbow.

The Dominant Grey budgerigar mutation, often called the Australian Grey or simply Grey, is one of approximately 30 mutations affecting the colour of budgerigars. It is the basis of the Grey-Green and Grey standard varieties.

The Dilute budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is one of the constituent mutations of several recognised varieties: the Light, Dark, Olive, Grey and Suffused Yellows and the Grey and Suffused Whites.

The Clearwing budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Clearwing variety, often known as Yellowwings in the green series and Whitewings in the blue series. When combined with the Greywing mutation the variety is known as the Full-bodied Greywing. When combined with the Yellowface II and Opaline mutations the Rainbow variety is produced.

The Greywing budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Greywing variety. When combined with the Clearwing mutation the variety is known as a Full-bodied Greywing.

The Opaline budgerigar mutation is one of approximately 30 mutations affecting the colour or appearance of budgerigars. It is the underlying mutation of the Opaline variety. When combined with the Yellowface II and Clearwing mutations the Rainbow variety is produced.

The Cinnamon budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Cinnamon variety and, with Ino, a constituent mutation of the Lacewing variety.

The Ino budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Albino and Lutino varieties and, with Cinnamon, a constituent mutation of the Lacewing variety.

Slate budgerigar mutation

The Slate budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Slate variety.

The Dominant Clearbody budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Easley Clearbody variety.

The German Fallow budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. At least three types of Fallow, the German, English, and Scottish, all named after their country of origin, have been established, although none of these types is common. They are superficially similar, but adult birds may be distinguished by examining the eye. All have red eyes, but the German Fallow shows the usual white iris ring, the eye of the English Fallow is a solid red with a barely discernible iris and the iris of the Scottish Fallow is pink.

The English Fallow budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. At least three types of Fallow, the German, English and Scottish, all named after their country of origin, have been established, although none of these types is common. They are superficially similar, but adult birds may be distinguished by examining the eye. All have red eyes, but the German Fallow shows the usual white iris ring, the eye of the English Fallow is a solid red with a barely discernible iris and the iris of the Scottish Fallow is pink.

The Scottish Fallow budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. At least three types of Fallow, the German, English and Scottish, all named after their country of origin, have been established, although none of these types is common. They are superficially similar, but adult birds may be distinguished by examining the eye. All have red eyes, but the German Fallow shows the usual white iris ring, the eye of the English Fallow is a solid red with a barely discernible iris and the iris of the Scottish Fallow is pink.

The English Grey budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It appeared briefly in the 1930s but was lost shortly after and until recently was believed to be no longer extant. However, the appearance of the anthracite budgerigar mutation in 1998 with a seemingly identical appearance and identical genetic behaviour, insofar as can now be determined, suggests the mutation may have been regained.

The Clearflight Pied budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Continental Clearflight and Dutch Pied varieties. The Dark-eyed Clear variety results when the Recessive Pied and Clearflight Pied characters are combined.

References


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