How Cell Work Introduction of Molecular Biology

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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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Replication
DNA
Reverse Transcription (Reverse Transcriptase)
Transcription (RNA Polymerase)
RNA
Genomics Proteomics
Translation
Protein
Post-translational Modifications (PTMs)
Cellular Functions
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Replication Semi-conservative
Preserving and propagating the cellular message
Replication begins at a predetermined site, the
origin of replication in a bidirectional mode.
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(Replication in vitro)
re
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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 at terminator 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
OD
b-galactosidase
Inada et al, Genes to Cells, 1, 293, 1996

• 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 b-galactosidase is somehow
  abolished in the presence of glucose.
• Question What is the mechanism that suppresses
  synthesis of lactose enzymes?

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Model of Lac Operon (animation)
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