Figure 5.

Nucleolar dominance is independent of rRNA gene dosage and ploidy. Two hexaploid B. napus-like lines (R1 and R2) having two diploid sets of B. oleracea chromosomes but only one set of B. rapa chromosomes were tested to see if doubling the dosage of B. oleracea rRNA genes could alter the dominance relationship. S1 nuclease protection assays show that B. rapa rRNA genes remain dominant (lanes 1 and 2) as in tetraploid B. napus (Fig. 4). Trace amounts of B. oleracea transcripts were detectable in the hexaploid lines (lanes 3 and 4). Size markers are shown in lane 5.