VII. DNA and Genome Structure

1
VII. DNA and Genome Structure
2
VII. DNA and Genome Structure A. Search for
the Genetic Information
3
VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work a.
Miescher 1868 isolated nuclein from the
nucleus of cells. An acidic, nitrogen rich
material.
4
VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work a.
Miescher 1868 isolated nuclein from the
nucleus of cells. An acidic, nitrogen rich
material. b. Levene - 1910 Chromosomes
consist of DNA and proteins. DNA was very simple
(4 nucleotides) whereas proteins were very
complex (21 amino acids).
5
VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work a.
Miescher 1868 isolated nuclein from the
nucleus of cells. An acidic, nitrogen rich
material. b. Levene - 1910 Chromosomes
consist of DNA and proteins. DNA was very simple
(4 nucleotides) whereas proteins were very
complex (21 amino acids). Levene found that
these nucleotides were in approximately an even
ratio, and he hypothesized a very simple
tetranucleotide structure that was similar over
its length.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work a.
Miescher 1868 isolated nuclein from the
nucleus of cells. An acidic, nitrogen rich
material. b. Levene - 1910 Chromosomes
consist of DNA and proteins. DNA was very simple
(4 nucleotides) whereas proteins were very
complex (21 amino acids). Levene found that
these nucleotides were in approximately an even
ratio, and he hypothesized a very simple
tetranucleotide structure that was similar over
its length. Given that the genetic system must
encode the diversity of life, it seemed likely
that the more complex molecule (proteins) was
responsible.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work a.
Miescher 1868 isolated nuclein from the
nucleus of cells. An acidic, nitrogen rich
material. b. Levene - 1910 Chromosomes
consist of DNA and proteins. DNA was very simple
(4 nucleotides) whereas proteins were very
complex (21 amino acids). Levene found that
these nucleotides were in approximately an even
ratio, and he hypothesized a very simple
tetranucleotide structure that was similar over
its length. Given that the genetic system must
encode the diversity of life, it seemed likely
that the more complex molecule (proteins) was
responsible. c. Chargaff 1940s A
T, C G disproving Levenes model.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths
1927 Streptococcus pneumoniae causes pneumonia,
meningitis, sepsis Virulent strain has a
polysaccharide capsule that protects the cell
from being engulfed by white blood cells and it
makes them appear smooth (IIIS).
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths
1927 Streptococcus pneumoniae causes pneumonia,
meningitis, sepsis Non-virulent strain has no
capsule and are killed by the immune system they
are rough (IIR).
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths
1927 Streptococcus pneumoniae causes pneumonia,
meningitis, sepsis If virulent IIIS are killed
by heat, they can be injected without causing
disease.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths
1927 Streptococcus pneumoniae causes pneumonia,
meningitis, sepsis If virulent IIIS are killed
by heat, they can be injected without causing
disease. Griffith found that a combination of
LIVE IIR and DEAD IIIS, both non-virulent
independently, would kill the mouse.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths
1927 Streptococcus pneumoniae causes pneumonia,
meningitis, sepsis If virulent IIIS are killed
by heat, they can be injected without causing
disease. Griffith found that a combination of
LIVE IIR and DEAD IIIS, both non-virulent
independently, would kill the mouse. Concluded
that the IIR received a HERITABLE transforming
factor from dead IIIS cells, and turned into
live IIIS cells.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths
1927 Streptococcus pneumoniae causes pneumonia,
meningitis, sepsis Thought it was a chemical
that induced capsule formation.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths 1927
b. Dawson 1931 Transformation in vitro (test
tube)
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments a. Griffiths 1927
b. Dawson 1931 Transformation in vitro (test
tube) c. Alloway 1933 Transformation with
an extract from hk-IIIS dont even need the
intact cells to cause a HERITABLE change in the
live IIR?IIIS What causes this heritable change
DNA, RNA, or protein?
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2. Major Experiments d. Avery, McCarty,
and MacLeod - 1944

1. Took hk-IIIS extract and added live IIR got
   transformation (control).

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2. Major Experiments d. Avery, McCarty,
and MacLeod - 1944

1. Took hk-IIIS extract and added live IIR got
   transformation (control).
2. Took hk-IIIS and added proteases that destroy
   proteins got transformation Transforming
   factor is NOT a PROTEIN

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2. Major Experiments d. Avery, McCarty,
and MacLeod - 1944

1. Took hk-IIIS extract and added live IIR got
   transformation (control).
2. Took hk-IIIS and added proteases that destroy
   proteins got transformation Transforming
   factor is NOT a PROTEIN
3. Took this solution, added RNAases got
   transformation Transforming factor is NOT an RNA

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2. Major Experiments d. Avery, McCarty,
and MacLeod - 1944

1. Took hk-IIIS extract and added live IIR got
   transformation (control).
2. Took hk-IIIS and added proteases that destroy
   proteins got transformation Transforming
   factor is NOT a PROTEIN
3. Took this solution, added RNAases got
   transformation Transforming factor is NOT an RNA
4. Added DNAases NO TRANSFORMATION transforming
   factor is DNA.

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2. Major Experiments d. Hershey and Chase
- 1952

1. Viruses replicate within a bacterium requiring
   the replication of the genetic information.

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2. Major Experiments d. Hershey and Chase
- 1952

1. Viruses replicate within a bacterium requiring
   the replication of the genetic information.
2. Viruses are about 50 DNA and 50 protein. Which
   goes inside the cell to cause change?

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2. Major Experiments d. Hershey and Chase
- 1952

1. Viruses replicate within a bacterium requiring
   the replication of the genetic information.
2. Viruses are about 50 DNA and 50 protein. Which
   goes inside the cell?
3. Labelled proteins with radioactive sulfur and DNA
   with radioactive phosphorus by growing virus on
   labelled bacteria for one generation.

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2. Major Experiments d. Hershey and Chase
- 1952
4) Then, they exposed normal bacteria to these
differentially labelled viruses.
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2. Major Experiments d. Hershey and Chase
- 1952
4) Then, they exposed normal bacteria to these
differentially labelled viruses. 5) Then they
shook the solutions, separating the viral
component from the bacterial component.
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2. Major Experiments d. Hershey and Chase
- 1952

• 4) Then, they exposed normal bacteria to these
  differentially labelled viruses.
• Then they shook the solutions, separating the
  viral component from the bacterial component.
• Both replicates confirmed that only DNA, and not
  protein, entered the cell and must be responsible
  for orchestrating viral reproduction. DNA is the
  genetic information.

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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments 3. Other Evidence
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments 3. Other Evidence a.
Mutagenesis
The wavelengths of radiation that cause damage to
the genetic information are the wavelengths
absorbed by DNA, not proteins.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments 3. Other Evidence a.
Mutagenesis b. Recombinant DNA Technology
1986 gene for luciferase (from fireflies) was
transferred to plant embryos. When they grew,
and then were injected with luciferin (the
enzymes substrate), the action of the enzyme
(oxidation of luciferin) releases light.
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VII. DNA and Genome Structure A. Search for
the Genetic Information 1. Early Work 2.
Major Experiments 3. Other Evidence a.
Mutagenesis b. Recombinant DNA
Technology c. RNA is the genetic
information in some viruses
RNA injected by virus can act directly (TMV), or
can be copied into DNA (retroviruses) and
inserted into the hosts genome and inherited
during host cell replication (HIV).
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work - Chargaffs
ratios
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work - Chargaffs
ratios - Astburys 3.4A periodicity
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling (CalTech) Nobelist
for describing helical structure of proteins,
turned his attention to DNA.
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling (CalTech) Nobelist
for describing helical structure of proteins,
turned his attention to DNA. He used X-Ray
crystallography, and with impure samples of DNA,
suggested DNA was a triple-helix
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling b. Maurice Wilkins
and Rosalind Franklin - The King College Lab,
Univ. of London. - They had a more purified
sample of DNA, but lab tensions made their
supervisor assign Wilkins the B form and
Franklin the A form. Wilkins concluded that
the B form was helical Franklin did not agree.
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling b. Maurice Wilkins
and Rosalind Franklin - However, her subsequent
work and beautiful x-rays ultimately convinced
her of a double-helical structure submitted to
journals in March 1953 but without describing a
specific model. Critical contributions were
confirming Astburys 3.4A periodicity, and
finding a larger periodicity at 34.0A.
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling b. Maurice Wilkins
and Rosalind Franklin c. Francis Crick and James
Watson - Cavendish Lab, Cambridge University.
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling b. Maurice Wilkins
and Rosalind Franklin c. Francis Crick and James
Watson - Cavendish Lab, Cambridge
University. - Crick was the crystallographer
and a modeller. - Were working on helical
structures with the backbone on the inside. On
seeing Franklins picture 51 in January 1953,
they changed direction and ultimately produced a
model of DNA that explained Franklins
regularities and Chargaffs Ratios.
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling b. Maurice Wilkins
and Rosalind Franklin c. Francis Crick and James
Watson - Cavendish Lab, Cambridge
University. - Crick was the crystallographer
and a modeller. - Were working on helical
structures with the backbone on the inside. On
seeing Franklins picture 51 in January 1953,
they changed direction and ultimately produced a
model of DNA that explained Franklins
regularities and Chargaffs Ratios. d. 1958
Franklin dies of ovarian cancer probably related
to her x-ray work.
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize a. Linus Pauling b. Maurice Wilkins
and Rosalind Franklin c. Francis Crick and James
Watson - Cavendish Lab, Cambridge
University. - Crick was the crystallographer
and a modeller. - Were working on helical
structures with the backbone on the inside. On
seeing Franklins picture 51 in January 1953,
they changed direction and ultimately produced a
model of DNA that explained Franklins
regularities and Chargaffs Ratios. d. 1958
Franklin dies of ovarian cancer probably related
to her x-ray work. e. 1962 Nobel Prizes for
Crick, Watson, and Wilkins
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize 3. The Structure of DNA
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts i.
pentose sugar
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts i.
pentose sugar ii. Nitrogenous base
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts i.
pentose sugar ii. Nitrogenous base
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts i.
pentose sugar ii. Nitrogenous base iii.
Phosphate group
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts i.
pentose sugar ii. Nitrogenous base iii.
Phosphate group - nucleotide diphosphates and
triphosphates can also occur, and two of these
(ATP and GTP) are energetically important, too.
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts -
nucleotides are linked by phosphodiester bonds to
form a helix
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts -
nucleotides are linked by phosphodiester bonds to
form a helix - typically, synthesis occurs by
adding new bases to the 3 hydroxyl group
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts -
nucleotides are linked by phosphodiester bonds to
form a helix - typically, synthesis occurs by
adding new bases to the 3 hydroxyl group -
the helix has a 5 to 3 polarity
3
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts -
nucleotides are linked by phosphodiester bonds to
form a helix - DNA double-helices have helices
that are complementary (base pair pairing)
A purine (A or G) always binds with a pyrimidine
(T or C) In fact, A with T (2 h-bonds) And G
with C (3 h-bonds)
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts -
nucleotides are linked by phosphodiester bonds to
form a helix - DNA double-helices have helices
that are complementary (base pair pairing)
and antiparallel (polarity is in opposite
directions).
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3. The Structure of DNA (and RNA) - basic unit
is a nucleotide, that has three parts -
nucleotides are linked by phosphodiester bonds to
form a helix - DNA double-helices have helices
that are complementary (base pair pairing)
and antiparallel (polarity is in opposite
directions).
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VII. DNA and Genome Structure A. Search for
the Genetic Information B. Determining DNA
Structure 1. Background Work 2. Race for the
Prize 3. The Structure of DNA 4. Function of
DNA and RNA overview
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4. Function of DNA and RNA overview i. DNA is
a template for RNA production (transcription)
GENE
DNA
RNA
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4. Function of DNA and RNA overview i. DNA is
a template for RNA production (transcription) ii
. RNA may be functional, or may itself be a
template for protein formation (translation).
DNA coding for RNA coding for proteins is called
the central dogma of genetics.
PROTEIN GENE
RNA GENE
DNA
RNA
Functional RNA (r-RNA, t-RNA)
M-RNA Protein-gene transcript
Protein
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4. Function of DNA and RNA overview i. DNA is
a template for RNA production (transcription) ii
. RNA may be functional, or may itself be a
template for protein formation (translation).
DNA coding for RNA coding for proteins is called
the central dogma of genetics. iii. Introns
are sequences in a gene (and the RNA transcript)
that are cut out of the RNA and are not
translated into protein sequence. Exons are the
coding sequences.
PROTEIN GENE
RNA GENE
DNA
exon
Initial RNA
(same process)
Transcript splicing
Functional RNA (r-RNA, t-RNA)
m-RNA
Protein
Post-translational processing