***è quello che intendo io... quella che a occhio potrebbe essere una focatura potrebbe geneticamente essere un'altra cosa. E si corre il rischio di buttare il bambino con l'acqua sporca. Il mosaicismo è un fenomeno a sé che non ha a che fare con le focature e... addirittura potrebbe non essere una faccenda strettamente "ereditaria" ma legata a mutazioni genetiche durante lo sviluppo dell'embrione.
Il mosaicismo è studiato soprattutto nel labrador retriever... googlando "mosaicism labrador" vi esce una caterva di roba, in inglese.
Labrador mosaic, riprodotti, hanno dato labrador normali.
nel bracco l'ipotesi è che le macchie che qui vedete nere siano arancio
qualche foto [media]http://www.labbies.com/mosaic.jpg[/media]
[media]http://trinitylabstexas.com/wp-content/uploads/2008/03/2344823615_defb202858.jpg[/media]
riassuntino in inglese
dallo stesso sito, trinity lab
mosaic indicates differences in the somatic tissue of heterozygotes that come about during mitotic division of somatic cells (recall from above that somatic cells are those that make-up the body). There are two possible ways by which an individual may become a mosaic. The first is called chromosome nondisjunction by which during division into daughter cells, one of the chromosomes fails to separate from its duplicated chromosome. As a result, one daughter cell receives an extra chromosome and the other receives an unpartnered-chromosome.
The second way that a mosaic may be produced is called chromosome loss by which the chromosome containing the dominant allele gets left behind when the daughter cell’s nucleus reconstitutes.
In either situation described above, the daughter cells of these altered somatic cells will contain the same alterations. As a result, one will observe a mosaic or brindled pattern of normal color mixed with color produced by the altered somatic cells. This condition has been reported in a Lab showing mosaic black and yellow coat color. When this Lab was bred to other Labs of normal coat colors of black, chocolate, or yellow, it was determined that the variation in color was not due to a mutated E locus allele (like the “ebr” allele) because none of the offspring demonstrated this phenotype. Rather, this coat characteristic was attributed to a chromosomal alteration as described above.
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