TheP-locus position effect inOenothera
InOenothera blandina, the genesPs,Pr andS produce a variegated phenotype when they are present in the interchange chromosome 3.11. When transferred by crossing-over to a normal 3.4 chromosome, they produce normal phenotypes. The variegation is therefore a position effect.
The break is 1·7 units from theP locus and 8·5 units from theS locus, indicating a considerable spread of the position effect along the chromosome. The action is thought to depend on translocation of theP andS loci to the neighbourhood of heterochromatin.
Theories of the mechanism of position effect are considered, but theOenothera case adds nothing new to the solution of the problem.
Volume 100, 2021
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