how cell work - introduction of molecular biology
TRANSCRIPT
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How Cell Work-Introduction of Molecular Biology
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Molecular biology: study the information flow and control of
cells.Central dogma is universal from the simplest to most complex
organisms.
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RNA
DNA
Protein
Transcription(RNA Polymerase)
Translation
Reverse Transcription(Reverse Transcriptase)
Post-translational Modifications (PTMs)
Cellular Functions
Genomics
Proteomics
Replication
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Replication: Semi-conservative
Preserving and propagating the cellular message
Replication begins at a predetermined site, the origin of replicationin a bidirectional mode.
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re
(Replication in vitro)
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Transcription:Sending the message
Sigma factor recognizes a specific sequence of nucleotide sequence (promoter) on a DNA strand. It is involved only in initiation.
Transcription stop atterminator sequence.
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DNA as the Template for RNA Synthesis
DNA as the Template for RNA Synthesis
RNA polymerase always reads in the 3’ to 5’-direction.One strand of DNA serves as the template or sense strand.
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Conserved sequences in promoters recognized by E. coli RNA polymerase
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Prokayrotic Promoter Sequences
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Model of Lac Operon (animation)
In procaryotes related proteins are often encoded without interspacing terminators. Transcription from a single promoter may result in a polygenic message.
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The lac operon mRNA.
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The genetic code (as written in RNA).
Universal Message
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Translation of an RNA message into a protein
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The diauxie
• When exposed to glucose + lactose, E. coli does not consume lactose until glucose is exhausted, resulting in two exponential growth phases separated by a lag. This is called the diauxie or “double growth.”• Diauxie occurs because synthesis of lactose permease and -galactosidase is somehow abolished in the presence of glucose.
Question: What is the mechanism that suppresses synthesis of lactose enzymes?
Inada et al, Genes to Cells, 1, 293, 1996
OD
-galactosidase
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