chiaraviglio@husc2.UUCP (lucius) (12/15/86)
In article <846@ulowell.UUCP>, rickheit@ulowell.UUCP (Erich Rickheit) writes: > . . .A yeast cell isn't really too much more complicated > than a virus, . . . Have you ever tried sequencing an entire yeast genome? Good luck, if you don't have something on the order of a Department of Energy grant and an extensive allocation of labor. It's on the order of 20 million base pairs of DNA (not counting the hundred thousand or so base-pairs of mitochondrial DNA) -- granted, this is small for a eukaryote, and some of it is introns and other non-coding DNA, but it is still more than most (or maybe all) prokaryotes, let alone VIRUSES (prokaryotes have a few hundred thousand to a few million base-pairs of DNA; viruses have up to a couple of hundred thousand base-pairs of DNA but are usually under 100000). More importantly, a yeast cell is structurally and chemically much more complicated than a virus. It has its own complete metabolism. The most a virus ever manages in the regard of metabolism other than that which it rips off from the host cell is a very limited number of functions such as coding for such things as a hyperspeed RNA Polymerase (SP6, T3(?), and T7 phages), an enzyme to synthesize a modified nucleotide (T4 phage -- needs to synthesize deoxyribo-hydroxymethylcytosine), or other similar functions (DNA Polymerases (T7 phage), Thymidine Kinase (some mammalian virus -- Herpes I think), RNA processing enzymes (Vaccinia (Cowpox) Virus), etc.). A yeast cell also has many different organelles -- functional organizations at a higher level than the molecular, wherease the structural organization of a virus is limited to the arrangement of core molecules, nucleic acid, capsid, and (optionally) envelope. Even prokaryotes are structurally more complicated than a virus, although it could be argued that their greater complexity of structural organization is mainly due to a greater number of different types of molecules and a generally greater size (but then check out such things as the electric motor (no kidding!) that runs the bacterial flagellae, and the molecular computational system that bacteria use to have some useful control over where they move). I am cross-posting this to sci.bio. Followups to this article should be posted there. -- -- Lucius Chiaraviglio lucius@tardis.harvard.edu seismo!tardis!lucius Please do not mail replies to me on husc2 (disk quota problems, and mail out of this system is unreliable). Please send only to the address given above.