Loop size in newt lampbrush chromosomes.

Lampbrush chromosome 11 from the newt Taricha granulosa was studied by scanning electron microscopy (SEM) to determine the size of all loops in this bivalent. Measurements with an XY digitizer revealed a mean loop length of 14.9 microns, with a large standard deviation and a skewed distribution toward higher values. The size of the loops at this stage of diplotene extension is similar to that reported in other eukaryotes studies with different approaches. We estimated, from the DNA content of chromosome 11, that between 0.4% and 2.2% of the DNA is found in the loops while the rest of the DNA must remain in the compact chromomeres.