Download Central Dogma and Structure of DNA

A lion hunter…
In The Jungle Dark…
And A Chinese Dentist…
And A British Queen…
All Fit Together
The 53rd Calypso Of Bokanon
• A lion hunter
• In the Jungle Dark
• And A Chinese
Dentist
• And A British Queen
• All Fit Together
• The Central Dogma of
Bokanon
What is Dogma?
DOGMA
• DEF: An
unshakeable,
commonly held
belief
• In biology, the
CENTRAL DOGMA
states that all life
demonstrates
continuity within
change over time
• We all “fit together”
How do we “all fit together” biologically?
The Central Dogma
• All life shares a
common language
for the synthesis of
protein
• The “language” is
the nucleic acid
5’-Deoxyribonucleic
Acid or “DNA”
The 3 Steps of The Central Dogma
1) REPLICATION
2) TRANSCRIPTION
3) TRANSLATION
What Makes A Language Efficient and Effective?
Characteristics of Effective Languages
• 1) Universal/Able to be used
by large numbers of
individuals
• 2) Efficiency in
communicating critical
information
• 3) Ability to be obtained and
used by successive
generations
• 4) Ability to prevent changes
that would diminish the
accurate passage of
information
• 5) Ability to repair or correct
changes that do occur
How does Deoxyribonucleic Acid
exhibit these characteristics?
Friedrich Miescher
• Obtained “acid-fast”
dye from World
Exposition of 1865
• In 1869, Miescher
extracted material from
the nucleus of
Leucocytes (white
blood cells) and was
able to stain them with
the acid-fast dyes
• First identification of
NUCLEIC ACIDS and
CHROMOSOMES
What Is The Function of Nucleic Acids?
Griffith Experiment
• Fred Griffeth 1928
• Streptococcus
pneumoniae has two
distinct forms
– Unencapsulated
– Encapsulated
– The encapsulated form
caused pneumonia but
the unencapsulated
strain does not cause
pneumonia
Griffith’s Protocol
• When either live
unencapsulated OR
dead encapsulated
bacteria were injected
into mice, they survived
• When dead
encapsulated bacteria
were mixed with live
encapsulated bacteria,
then injected, the mice
died of pneumonia
• Examination of the mice
showed high levels of
encapsulated bacteria
Significance of Griffith Experiment
• There is something inside of cells that
determines their traits.
• This substance is merely a component or
part of the cell
• When transferred to another cells, this
substance can transform the traits of
another organism
What do these results mean?
Avery’s Experiment
• Oswald T. Avery 1943
• Transformed bacteria
merely by exposing
them to the chromatin
(DNA & Protein)
obtained from other,
toxic bacteria
What do these results mean?
Significance of Avery’s Experiment
• The transformative substance inside of
cells is the chromatin
Hershey & Chase
• Alfred Hershey &
Martha Chase 1952
• Infected bacteria with
BACTERIOPHAGES
(viruses)
• The protein capsule of
bacteriophages
contains sulfur but not
phosphorus
• The nucleic acids of
bacteriophages do not
contain sulfur but do
contain phosphorus
Hershey & Chase Results
• When bacteriophages
infected bacteria, they
left the sulfur outside
of the bacterial host
cells
• The phosphorus was
passed into the host
cells
What do these results mean?
Significance of Hershey & Chase
• Protein was not causing the changes in
the host cells
• The transformative substance must be
the nucleic acid, 5’-Deoxyribonucleic
Acid
The Transforming Principle
• The information for
the traits/features of
an organism is
contained in the
nucleic acids
• If another organism
receives these nucleic
acids, it may express
the same traits as the
original
How does the structure of
5’-Deoxyribonucleic Acid Cause These
Changes In Living Organisms?
Levine Experiment
• P.A. Levine (1920)
• Building upon
Miescher’s
identification of DNA
as an acidic
substance, Levine
identified the
constituant parts of
Deoxyribonucleic Acid
• Three parts constitute
a NUCLEOTIDE
NUCLEOTIDE MONOMERS
• Deoxyribose (pentose carbohydrate/sugar)
• Phosphoric Acid
• Nitrogenous Bases
Purines
• Adenine (A)
• Guanine (G)
• Adenine forms two
hydrogen bonds
• Guanine forms three
hydrogen bonds
Pyrimidines
• Cytosine (C)
• Thymine (T)
• Thymine forms two
hydrogen bonds
• Cytosine forms three
hydrogen bonds
Chargaff’s Ratios
• Erwin Chargaff
• Chemical analysis of
nucleic acids obtained
from several different
species were
compared regarding
the relative
proportions of the four
nitrogenous bases
What Do These Results Mean?
Source
%A
%G
%C
%T
Human
Liver
Human
Thymus
Herring
Sperm
Yeast
30.3
19.5
19.9
30.3
30.9
19.9
19.8
29.4
27.8
22.2
22.6
27.5
31.7
18.2
17.4
32.6
Complimentary Base Pairing
• Due to their
complimentary
numbers of hydrogen
bonds, only certain
nitrogenous bases
may pair
• Adenine-Thymine
• Cytosine-Guanine
Structure of A Nucleotide
• Nucleotides are made
of three parts
• PO4 attached to 5’
carbon of deoxyribose
• Nucleotides may be
linked together as a
polymer via
dehydration synthesis
• -OH removed from
3’carbon of
deoxyribose and H
removed from PO4
group
Look Familiar?
How does the form of DNA allow
itself to be replicated?
Pauling’s Experiment
• Linus Pauling
• Showed that the form
of proteins in the
nucleus of living
organisms were often
twisted into a helix
X-Ray Crystallography
• Bombarding
biomolecules with xray radiation and
exposing the result to
a photographic plate
reveals the shadow of
the biomolecule
• Using the shadow,
the shape of the
biomolecule may be
deduced
Wilkins & Franklin
• Maurice Wilkins and
Rosalind Franklin
exposed DNA to Xray bombardment and
photographed the
result
• Franklin’s photos of
DNA indicated that it
was a helix
Watson & Crick
• James Watson &
Francis Crick (1953)
• Using data from
Chargaff & Franklin,
they determined that
DNA must be a
double (not single)
helical polymer
Modeling DNA
• Through construction
of a model, Watson &
Crick determined that
by using the
complimentary base
pairing of A-T & C-G,
DNA could attain a
double helix shape
The Significance of Watson & Crick
• Provided an
explanation for how
all the “parts” of DNA
could be arranged in
a manner that would
allow the molecule to
replicate itself
• 1st Part of Central
Dogma
During mitosis, the supercoils of DNA may
be further condensed into chromosomes