RE: question on merle gene
2011-10-17
Svara ▼
George Strain
Till Bodil Carlsson
The gene in question comes in two forms: dominant (M), called merle, and recessive (m). Every dog has two copies of the gene, one from each parent (MM, Mm, or mm). To get the merle phenotype – the pattern of light and dark pigmented areas – a dog must have at least one copy of M; these are known as single merles. It is uncommon, but not numerically documented, for single merles to have auditory or visual disorders. It can happen, but is not frequent. If a dog inherits two copies of the dominant allele (double merle, homozygous M, or MM), the chances of visual or auditory disorders is much greater but still not necessarily a predictable outcome; my work suggests that the impact may vary between breeds. Dogs homozygous for the recessive allele (mm) have no sign of the phenotype and no auditory or visual disorders. Auditory and visual problems are the result of the merle gene affecting the behavior of pigment cells in the eye or in the cochlea – we don’t know why some dogs are affected and others are not.
MM catahoulas can be heavily pigmented – I’ve seen a good number of them and confirmed their genotype from DNA tests (no longer available to me). In these cases the impact of the merle gene – both in the skin and in the ear and eye – is somehow constrained. There probably are multiple genes that modify the action of merle (and piebald, the other gene linked to deafness). We have much to learn. If I could predict the outcomes I could probably become fairly affluent.
Mail från George Strain 17 oktober)
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