Lecture 8 Flashcards
Flow of genetic info in eukaryotes
- each gene transcribed individually into a single mRNA
- replication and transcription occur in nucleaus
- RNAs must be exported out of nucleus for translation
Flow of genetic info in prokaryotes
- multiple genes may be transcribed in one mRNA
- coupled transcription and translation occur = more proteins
Termination of RNA synthesis is covered by…
a specific DNA sequence
intrinsic terminators
transcription is terminated w/o any additional factors
Rho-dependent termination
Rho protein recognizes specific DNA (RNA) sequences and causes a pause in RNA pol.
unit of transcription
unit of chromosome bounded by sites where transcription of DNA to RNA is initiated and terminated
examples of RNA that a re not translated
rRNA, tRNA
typesof rRNA
16S, 23S, 5S
rRNA and tRNA are very..
stable
tRNA cotranscribes with…..
rRNA or other tRNA
mRNAs have…
short half lives (few mins)
Prokaryotes often have genes clustered together and these genes….
are transcribed all at once as a single mRNA
polycistronic mRNA
an mRNA encoding a group of cotranscribed genes
operon
a group of related genes cotranscribed on a polycistrochaperonsnic mRNA
-allows for expression of multiple genes to be coordinated
chaperones
assist other proteins for proper folding or for assembly into larger complexes
signal sequences
found at the beginning of on proteins requiring transport from cell and prevent protein from completely folding
signal sequences signal…
the cell’s secretory system (Sec system)
The Tat system
secretion of folded proteins
tat protein export system
different from Sec export proteins that fold in cytoplasm
Types i to VI Secretion Systems
-large complex of proteins that form channels through membranes
Types II and V Secretion Systems
depend on Sec or Tat
Tyes I, III, IV, and VI Secretion Systems
do not require Sec or Tat
