Nuclear Architecture/Overview. Double-membrane envelope Has lumen that is continuous with ER Outer membrane also has ribosomes like ER Nuclear envelope has pores large, complex structures with octahedral geometry allow proteins and RNAs to pass
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Stars indicate heterogeneity in the nucleolus.
c – pores “face on” view thru tunnel
d – partially assembled ribosomes passing through pores (side view)
Fig. 1.37, Buchanan et al.
Nucleolus dumping something??
Nucleolus chromatin spread
RNA Pol I making pre-rRNAs
SV40 virus minichromosomes with a nucleosome-free zone at its twin promoters.
Can also be shown for cellular genes by DNase I digestion of chromatin – promoter regions are hypersensitive to DNase I.
Packing ratio ~ 25 for this step = 1000 overall
x 1000 to get bp
Lilium longiflorum (Easter lily) = 90,000 Mb
Fritillaria assyriaca (butterfly) = 124,900 Mb
Protopterus aethiopicus (lungfish) = 139,000 Mb
How many genes do plants have?
Texas wild rice
Science 286, 2165 (1999)