Systems Microbiolo29

Systems Microbiolo29 - o Halfway through the sigma factor...

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Systems Microbiology long). DNA polymerase I (not III) is used on the lagging strand, so that it will eat through the extra primers (polymerase I would stop). ° An RNA primer is laid down by a primase. ° The primers have to be removed. ° Nicks have to be removed by DNA ligase. ° With a circular DNA, the replication happens circularly (a bubble opens up between the strands, and replication happens there). • This is generally what happens with prokaryotes. • But there are also some that have linear DNA. ° Regulatory Pathways in prokaryotes – the larger topic of today’s lecture. o The more important means of cell regulation is transcription. ° Prokaryotic transcription o DNA is more stable than RNA, while RNA can be turned over and used faster than DNA. o The 2’ hydroxy group of RNA is useful here. o RNA polymerase does not need a primer – it just transcribes directly.
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Unformatted text preview: o Halfway through the sigma factor falls off. o Pribnow box and -35 region. o Some bases are more highly conserved than others. Also, some organisms are more GC-rich than others. o There are different types of sigma factors ° Sigma 70 – kind of the vanilla flavor – used for “normal” promoters ° Sigma 32 is used for heat-shock promoters ° Sigma 54 is used for N limitation promoters o There’s a modularity in how cells can turn on all kinds of different genes. o Strong versus weak promoters. o Initially RNA polymerase binds, the strand is opened up, and transcription begins. o Transcription termination ° Inverted repeats – these connect to each other, stopping transcription, and they require no extra factors. ° Row dependent terminations – require extra proteins ° There are other sorts as well...
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