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

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Chapter 7The Blueprint of Life,from DNA to
Protein
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Where weve been

• Our bacterium has
• Entered the hosts body through the Portal of
  Entry.
• Adhered to the hosts cells
• Competed with hosts normal microbiota
• Successfully defended itself against the host
  immune system (more in Stage 03)
• Found the right environment (pH, temperature,
  oxygen requirement, and water availability)
• Found and transported in the right nutrients
• And, finally, through catabolic reactions,
  harvested energy and made precursor metabolites
  that were made into subunits.

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Metabolism

• The sum total of ALL chemical reactions within a
  cell
• Catabolic
• Anabolic

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Where were going

• Now we are going to take those subunits
  (nucleotides, amino acids, monosaccharides,
  glycerol and fatty acids) and put them together
  to make macromolecules so we can make another
  bacterial cell.
• Nucleotides --gt nucleic acids (RNA, DNA)
• Amino acids --gt proteins
• Monosaccharides --gt polysaccharides
• Glycerol fatty acids --gt lipids

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Where were going

• Now we are going to take those subunits
  (nucleotides, amino acids, monosaccharides,
  glycerol and fatty acids) and put them together
  to make macromolecules so we can make another
  bacterial cell.
• Nucleotides --gt nucleic acids (RNA, DNA)
• Amino acids --gt proteins
• Monosaccharides --gt polysaccharides
• Glycerol fatty acids --gt lipids

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Making macromolecules!

• DNA nucleotide subunits --gt DNA Replication to
  make DNA.
• RNA nucleotide subunits --gt Transcription to make
  RNA.
• amino acid subunits --gt Translation to make
  proteins.

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What do you know about DNA?

• Chromosomes made of DNA contain an organisms
  entire genome
• DNA codes for genes.genes code for proteins
• Chemical composition is nucleotides
• It exists in most cells as a double stranded
  structure

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DNA Structure
DNA Base Pairing A-T G-C
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DNA Structure
DNA Base Pairing A-T G-C
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DNA Replication
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Enzymes necessary for DNA replication more about
enzymes!

• DNA gyrase, Helicase, Primase, DNA polymerase,
  DNA ligase

http//www.chem4kids.com/files/bio_enzymes.html
From http//waynesword.palomar.edu/molecu1.htm
http//www.chem4kids.com/files/bio_enzymes.html
Enzymes can break molecules apart
Enzymes can put molecules together
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Nucleotides are added to the 3 position (OH
group)
DNA Base Pairing A-T G-C
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DNA replicationa closer look
DNA polymerase polymerizes DNA nucleotides
together in the 5 -gt 3 direction to make
DNA. DNA polymerase requires a primer (short
stretch of nucleotides) and a template in order
to begin work.
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DNA replicationcloser look
http//www.youtube.com/watch?vyqESR7E4b_8
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Where were going

• We just put DNA nucleotides together to make DNA
  during DNA Replication.
• Now we have to make more proteins needed to build
  our new cell.

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Gene Expressionwhy is it important?

• Transcription
• Translation

In order for our cell to replicate, it needs to
make the proteins that are needed to build that
new cell. DNA has the blueprints (genes) for
making these proteins.
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Transcription RNA is transcribed from DNA
Comparing bases DNA G, A, T, C RNA G, A, U,
C Base Pairing DNA-RNA G-C A-U
T-A C-G
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Transcription DNA to RNA

• Requires an enzyme - RNA polymerase
• RNA nucleotides
• Base pairing rules for building RNA from a DNA
  template
• Process proceeds in the direction 5---gt3
• Process begins at the promoter region and ends at
  the terminator sequence

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Transcription RNA synthesis
Base Pairing DNA-RNA G-C A-U
T-A C-G
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Transcription Promoter orients direction of
transcription
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What are the possible products from transcription?

• Messenger RNA (mRNA)
• Encodes the message for a protein.
• Transfer RNA (tRNA)
• Essential component to translate RNA language
  into amino acid language during translation.
• Ribosomal RNA (rRNA)
• Together with protein, this makes up the
  structure of a ribosome.

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Translation RNA to protein

• What is needed for the process?
• mRNA
• Amino acids
• tRNA
• Ribosomes

Speaks both amino acid language AND RNA
language! Able to translate the RNA code into
amino acids!
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Translation RNA to protein

• What is needed for the process?
• mRNA
• Amino acids
• tRNA
• Ribosomes
• Connects amino acids
• together to make a protein!

Large subunit
Small subunit
Prokaryotic ribosome
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The Genetic codeTranslating RNA to amino acids
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Translation
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Translation
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Translation reading frame determines the protein
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Both processes occur at the same time in bacteria
because the DNA is not separated from the
ribosomes (like in eukaryotic cells!)
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Is it important to regulate protein synthesis?

• Yes!
• Genes to produce enzymes for glucose metabolism
  are constitutive (always made)
• Other genes are inducibleonly made when needed
  (lactose operon)
• Other genes are repressibleturned off when not
  needed (tryptophan operon)

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Models for transcriptional regulation with
repressors
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Transcriptional regulation by activators
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Lactose Operon as a model

• Used to understand control of gene expression in
  bacteria
• Operon consists of three genes needed to degrade
  lactose
• Repressor gene(codes for repressor protein)
  outside of operon coding region inhibits
  transcription unless something else bind to the
  repressor protein

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Lactose Operon
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Diauxic growth curve of E. coli
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What conditions are needed for the lactose operon
to be turned on?

• No glucose
• Increasing levels of cAMP
• cAMP binds to CAP, then complex binds next to
  lactose operon promoter at the activator region
• RNA polymerase binds to promoter
• Lactose present
• Allolactose binds to repressor, keeping it from
  binding to the operator
• RNA polymerase can transcribe the gene

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How do organisms adapt to other changes in their
environment?

• Some organisms turn genes on/off as needed
• Some organisms alter gene expression

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Gene regulation systems in bacteria

• Signal transduction
• Two component regulatory system
• E. coli use this system to sense if nitrate is
  present when in an anaerobic environment. It
  turns on genes to use nitrate as the terminal
  electron acceptor for use in anaerobic
  respiration!

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Gene regulation systems in bacteria

• Signal transduction
• - Quorum sensing
• Quorum sensing turns on biofilm production!

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Metabolism

• The sum total of ALL chemical reactions within a
  cell
• Catabolic
• Anabolic

DNA Replication
Transcription
Translation