"Lampbrush" chromosomes in a eukaryote
visible DNA strand is
transcribed by a series of closely-packed RNA polymerase (RNAPol)
molecules moving serially along the strand. Each RNAPol
trails a filament corresponding to an rRNA transcript. Note
direction of transcription is towards the broad end of the lampbrush: the
longest filaments trail from
an RNAPol that
the oocytes of an amphibian, the European crested newt (Notopthalmus).
Instead of condensing during meiotic prophase, they remained uncoiled
so as to
allow extensive transcription of rRNA genes to make the large
number of ribosomes
necessary for early development. In this case, therefore, the RNA transcript is not translated.
© 2000 by Griffiths et al. ; text © 2008 by Steven M.