Chapter 7: The Blueprint of Life, from DNA to Protein

1
Chapter 7The Blueprint ofLife, fromDNA to
Protein
2
Important Point
If you are having trouble understanding lecture
material Try reading your text before
attending lectures. And take the time to read it
well!
3
Molecular Genetics Overview

• Genome cells complete set of genetic
  information.
• In practice genome does not include plasmids.
• Genome, for most bacteria, is synonymous with
  chromosome (since chromosome is singular for most
  bacteria).
• The genome of all cells consists solely of DNA.
• For some viruses the genome is RNA, however.
• Genes are the most noteworthy aspect of genomes.
• Traditionally, most genes encode proteins (though
  in reality a great number of genes instead encode
  individual polypeptides or non-mRNA RNAs).
• Central Dogma of Molecular Genetics
• Replication DNA to DNA information transfer.
• Transcription DNA to RNA information transfer.
• Translation RNA to protein information
  transfer.
• Reverse transcription DNA to RNA information
  transfer.

4
Central Dogma
Transcription, catalyzed by RNA Polymerase, is
the first step of Gene Expression.
Translation is catalyzed by Ribosomes.
5
Representations of DNA Structures
Double helix.
Closed-circular DNA.
dsDNA
ssDNA
6
RNA Transcription
ssRNA
mRNA strand
7
RNA Transcription
Medically, transcription is important during
antibiotic therapy as well as for virus
identification characterization.
8
Promotion of Transcription
Note different DNA strands serving as templates.
Note consistency of 5 to 3 orientation.
9
RNA Synthesis Overview
Upstream
Downstream
10
Pro- vs. Eukaryotic Gene Expression
11
Some Sequenced Microbes
12
Mycoplasma genitalium ORFs
Each Open Reading Frame (ORF) one gene as
inferred from the complete sequence of M.
genitalium.
13
Additional Terms/Concepts

• Constitutive expression genes that are
  expressed whenever protein synthesis occurs,
  usually housekeeping genes (central to
  metabolism).
• Inducible expression genes that are normally
  turned off but are expressed under certain
  conditions, e.g., to use new carbon/energy source
  (catabolism).
• Repressible expression genes that are normally
  expressed, but are turned off under certain
  circumstances, e.g., when sufficient quantities
  of a factor (such as an amino acid) is present
  (anabolism).
• Operon set of genes expressed from same
  polycistronic message that are expressed
  simultaneously.
• Quorum sensing control of gene expression based
  on bacterial density (i.e., existence of a
  quorum).

14
Link to Next Presentation