Molecular Biology

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Molecular Biology

• Introduction
• Definitions
• History
• Central Dogma

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Molecular Biology

• Definitions
• Chromosomes
• DNA
• Gene
• Genotype
• Phenotype

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Molecular Biology

• Chromosomes
• The structure in cells that carries hereditary
  information
• Composed of DNA and protein
• Prokaryotic - circular
• Eukaryotic - linear

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Molecular Biology

• DNA
• Nitrogenous base (4 bases - A,T,G C
• Deoxyribose sugar
• Phosphate
• Nitrogenous bases are paired
• AT
• GC
• Double helix structure

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Molecular Biology

• Genes
• Segments of DNA
• Functional or regulatory
• Mutability and variation

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Molecular Biology

• Genotype
• The genetic make-up of an organism the
  information that codes for all the
  characteristics of an organism
• Phenotype
• The expression or physical manifestation of a
  gene how it appears

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Molecular Biology

• Molecular biology seeks to understand the
  molecular or chemical basis of genetics
• History of molecular biology is a melding of
  biochemistry, especially nucleic acid
  biochemistry and genetics

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Molecular Biology

• Biochemistry
• Meischer
• Avery MacLeod
• Hershey Chase
• Watson Crick

• Genetics
• Mendel
• Sutton
• Morgan
• Griffith
• Delbruck
• Beadle Tatum
• Tatum Lederberg

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Molecular Biology - Genetics

• Mendel (1865)
• Fluid vs. particulate inheritance
• Studied pure breeding pea plants
• Law of Segregation
• Law of Independent Assortment
• Rediscovered by de Vries others

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Molecular Biology
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Molecular Biology
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Molecular Biology - Genetics
Cross of pure breeding purple flowers with pure
breeding white flowers produces all purple plants
with genotype Pp crossing Pp plants produces
following distribution
P p
P PP purple Pp purple
p Pp purple pp white
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Molecular Biology - Genetics

• Walter Sutton (1902)
• Studied meiosis in grasshoppers (insects have
  large readily observable chomosomes)
• Observed that chromosomes behave in manner
  similar to segregation of hereditary material
• Found that chromosomes occur in morphologically
  similar pairs
• Pairs separate during meiosis

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Molecular Biology - Genetics
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Molecular Biology - Genetics

• Morgan
• Developed modern science of genetics
• Used fruit flies because they had a shorter
  generation time than peas
• Discovered sex-linkage
• Students developed techniques of mapping genes on
  chromosomes

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Molecular Biology - Genetics

• Griffith
• discovered transformation in 1927
• is a means of genetic transfer in microorganisms
• a process by which a nonpathogenic strain is
  transformed into a pathogenic strain

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Molecular Biology - Genetics
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Molecular Biology - Genetics

• Delbruck
• developed quantitative methods for analysis of
  bacteriophage viruses of bacteria
• organized course to teach biologists methods at
  Cold Spring Harbor resulting in a large number of
  biologists trained in molecular techniques

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Molecular Biology - Genetics

• Beadle Tatum
• developed Neurospora as an experimental organism
• established one gene one enzyme hypothesis
• generation time is even shorter with Neurospora

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Molecular Biology - Genetics
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Molecular Biology - Genetics
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Molecular Biology - Genetics

• Tatum Lederburg
• discovered conjugation in bacteria

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Molecular Biology - Biochemistry

• Meischer (1869)
• Austrian doctor
• isolated a substance called nuclein from the
  nuclei of cells obtained from the pus of surgical
  bandages
• found to contain nitrogenous chemicals, sugar and
  phosphate

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Molecular Biology - Biochemistry

• Avery MacLeod (1944)
• isolated Griffiths transforming factor to a high
  degree of purity
• characterized transforming factor using highly
  purified enzymes
• found transforming factor to be DNA

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Molecular Biology
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Molecular Biology - Biochemistry

• Hershey Chase (1952)
• used newly developed radioisotopes
• 35S for protein
• 32P for nucleic acid
• labeled bacteriophage (a virus of bacteria)
• found 32P went into cells but 35S did not
  implying that nucleic acid transfer information
  to cell for new bacteriophages

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Molecular Biology - Biochemistry

• Watson Crick (1953)
• used X-ray crystallography to study structure of
  DNA
• by combining chemical data and X-ray data were
  able to construct a model of DNA
• structure inferred function leading to Central
  Dogma

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Molecular Biology

• Central Dogma
• DNA Structure
• Genetic Code
• Replication
• Transcription
• Translation

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Molecular Biology

• DNA Structure
• Sugars
• Bases
• Phosphates
• Double Helix
• Anti-parallel

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Molecular Biology

• Genetic Code
• 4 bases / 20 amino acids
• codons
• punctuation

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Molecular Biology
Universal Genetic Code
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Molecular Biology

• Central Dogma states a hypothesis regarding
  information flow in cell
• Replication - the copying of DNA or information
  for next generation
• Transcription - the copying of information for
  use by the cell
• Translation - the conversion of information into
  useful products -enzymes

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Molecular Biology
Replication
Transcription
Translation
Protein
DNA
mRNA
mRNA tRNA Ribosomes
RNA Polymerase
DNA Polymerase
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Molecular Biology

• Replication
• replication is semi-conservative
• replication occurs at replication fork
• replication is discontinuous process
• uses DNA polymerase
• Uses RNA polymerase
• requires a primer with free 3-hydroxyl

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Molecular Biology
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Molecular Biology
The Meselson Stahl Experiment
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Molecular Biology
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Molecular Biology
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Molecular Biology
Continuous/Discontinuous DNA Synthesis
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Molecular Biology

• Transcription
• RNA polymerase
• promoters
• produces messenger RNA (mRNA)
• requires NO primer

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Molecular Biology
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Molecular Biology

• Differences between prokaryotic and eukaryotic
  mRNA
• Prokaryotic
• often polygenic
• turns over quickly
• translated almost immediately
• Eukaryotic post transcription modification
• Heterogenous introns exons - excision of
  introns
• mRNA stability days to weeks
• Addition of 5 cap and 3 polyadenylation

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Molecular Biology

• Translation
• tRNA
• amino acid synthase
• ribosomes
• initiation
• termination

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Molecular Biology
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Molecular Biology

• DNA Sequence Analysis
• DNA coding (sense)
• 5CCG ATG AAT GTC GAG CTA TCC TAC 3
• DNA non-coding (nonsense)(template)
• 3GGC TAC TTA CAG CTC GAT AGG ATG 5
• mRNA
• 5CCG AUG AAU GUC GAG CUA UCC UAC 3