L15 - prokayotic gene expression 4 Flashcards
why is transcriptional control favoured in prokayotes
- transcription happenes at same time as translation
= rapid reponses can have affect on transcriptional level unlike in eukaryotes
- prokayotic mRNA has short life
= why make somnthing that cant be used or stored
= better just not to make it
- takes a lot of ergy to produce unused mRNA
wjhat are the 2 key components of prokaryoitc ribosome
70s ribosome = 50s and 30s subunits
which part of the ribosome binds to the ribosome-binding site
RBS is bound by 16s rRNA component of the 30s subunit
RBS is specific sequnce upstraem of start codon and is always the same sequnce
how is translation at ribosomes/translation controlled by RNA-binding proteins
repressors bind to RBS preventing binding of mRNA
how can riboswitcjes affect translation at ribosomes in prokaryotes
binding of ligand causes hairpin loop to form in RBS
= double stranded RBS
= ribosome cannot bind = no translation
how can regulatory RNAs cause activation and repssion at ribosomes in prokaryotes
repression:
RNA binds to RBS = ribosome cant bind
activation:
RNA binds to hairpin loop formed over RBS
RNA binds stronger to the loop than the loop does to RBS
= comes aprt
= RBS is free
what is an operon
multiple genes for proteins placed within a single promoter and terminal sequnce
multiple RBS sequnces
= ribosome binds –> produce protein –> falls off —> binds to next RBS
what is coupled translation and how can it go wrong
genes very close togther in single operon
ribosome that disosociates at end of gene 1 rapidly asociates onto following RBS for gene 2
mutations in gene can produce premature stop codons
= prevent coupled translation
= decreased production of downstream protein
