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How Cell Work - Introduction of Molecular Biology.

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Presentation on theme: "How Cell Work - Introduction of Molecular Biology."— Presentation transcript:

1 How Cell Work - Introduction of Molecular Biology

2 Molecular biology: study the information flow and control of cells. Central dogma is universal from the simplest to most complex organisms.

3 RNA DNA Protein Transcription (RNA Polymerase) Translation Reverse Transcription (Reverse Transcriptase) Post-translational Modifications (PTMs) Cellular Functions Genomics Proteomics Replication


5 Replication: Semi-conservative Preserving and propagating the cellular message Replication begins at a predetermined site, the origin of replication in a bidirectional mode.

6 rere (Replication in vitro)

7 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.

8 DNA as the Template for RNA SynthesisDNA 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.

9 Conserved sequences in promoters recognized by E. coli RNA polymerase

10 Prokayrotic Promoter Sequences

11 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.

12 The lac operon mRNA.

13 The genetic code (as written in RNA). Universal Message

14 Translation of an RNA message into a protein



17 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

18 Model of Lac Operon (animation)



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