Let (X c) represent the recessive allele that causes colorblindness and (X +) represent the normal dominant allele.

One example of an X-linked trait is red-green colorblindness. Affected individuals may not see the number 6. An Ishihara plate can be used to test for red-green colorblindness. Most X-linked traits in humans are recessive. Females will have two X-linked alleles (because females are XX), whereas males will only have one X-linked allele (because males are XY). X-linked alleles require a specific notation: X c or X + where the “+” represents the dominant allele and the lowercase letter the recessive allele. So what do we do with these genetic symbols? We go back to the Budgie Genetics and learn about the different types of inheritance.Traits that are determined by alleles carried on the X chromosome are referred to as X-linked. This list can be found on the MUTAVI website. It tends towards the internationally agreed symbols, but you may find other lists that use different ones also. There is a list of the genetic symbols for the various budgie colours and varieties that I prefer. It makes sense to adopt the same naming system as used in other species, but I'm not sure that will happen.

For example we tend to call the par blue varieties in budgies yellow face blue. However, for some reason (probably because budgies are very popular and the clubs large enough to be separate from other clubs) budgie breeders named some of the mutations differently and do not want to change to conform. Generally the same name is used when the same mutation occurs in different species, so there are a number of species that have the par blue mutation. Genetic Symbols for Budgie Colours and VarietiesĪs already mentioned many of the genes present in budgies are also present in other parakeets. Genotype = what genes your budgie has, a list of the genes that produce the budgies phenotype. Phenotype = what your budgie looks like, a description of its physical appearance. Heterozygous = two alleles different, so a budgie with bl +/bl 1 would be said to be heterozygous, or 'split' for the mutated blue gene (called green split blue and written as green/blue).įinally there are two more useful terms that you are bound to come across: Homozygous = two alleles the same, so a budgie with bl +/bl + would be said to be homozygous for the wild type blue gene. Next we need terms to describe a bird with two alleles the same (like bl +/bl + or bl 1/bl 1) or two that are different (like bl +/bl 1): So here we have them:Īs a budgie has two copies of each gene there are three possible combinations of the above genes that any budgie can have.īl +bl + = two genes for green colour bl +/bl 1 = one gene for green and one for blue bl 1/bl 1 = two genes for blue A Couple of Useful Genetic Terms In our example bl 1 is recessive to the wild type of green so this genes symbol is always written in lower case. Page.) So an allele that is dominant to wild type is written in upper case and theĪllele that is recessive is written in lower case. (For more information on these types of inheritance go back When a gene mutates the new allele is usually either dominant or recessive to the original wild type. We can now easily distinguish which allele of the blue gene we are talking about. In our example the wild type allele is bl + and the allele which produces a blue bird is bl 1. Symbol - the symbol for a gene is usually the first two or three letters of the gene name, in this case: bl, and the original wild type version of a gene is also given a +. (As there are two genes that produce the blue phenotype in budgies, it is in How do we name and decide on the symbolĮffects of the mutated gene, so in this case the gene is know called blue. The gene responsible the wild type green colour mutated so that it I will use the internationally agreed system where ever possible. It makes sense to follow a system so everyone is using the same name for the same gene, however, budgerigar clubs tend to stick to what their members are used to instead. There is an international agreement on how names and symbols are used as the same genes and mutations are present in many parakeet species. Sometimes it is helpful to use genetic symbols rather than writing theįull name of each gene.

Symbol for female genetic