To the group,
Previously, this query :
AB>> Plant primary transcripts (not just arabidopsis, but most
AB>> plants) tend to be smaller than animal transcripts, as plant
AB>> transcriptional units, like animals, have introns, but the introns
AB>> are small. Does anybody have a nice quotable reference (or two)
AB>> stating an average size for animal vs plant transcriptional units?
AB>> I would think this kind of thing would be in a textbook, but it
AB>> isn't... I do have "Molecular Biology of the Cell" which sets the
AB>> average animal pol II primary transcript at 7kb.
I take this paraphrase, without permission, from "Isolating Plant Genes"
by S. Gibson and C. Somerville, TIBTECH 11 (July 1993). :
Average tobacco mRNA is 1.34 Kb (Goldberg et al, Cell 14, 123-131).
Average weed gene has 3.13 introns, average cDNA has 161 bp and 232
of UTR at 5' and 3' ends, respectively (analysis of Genbank release 70).
Average dicot intron is 215 bp (Goodall and Filipowitz, PMB 14, 727-733).
Therefore, "average size of primary transcripts in Arabidopsis" = 2.4 Kb.
Furthermore (from same) :
Assume average (pol II-transcribed) gene contains .4 and .2 Kb at 5' and 3'
ends respectively, for transcription regulation, then the average gene
is 3.0 Kb.
Depending on the estimate of genome size, and assuming adjacent genes there
are from 21000 to 43500 genes in Arabidopsis.
bosborne at nature.berkeley.edu