Download Protein Synthesis - Sonoma Valley High School

DNA, RNA And
Protein
Synthesis
Function of DNA
Modern Biology
Pages 193 - 195
Structure of
DNA must
allow the
storage and
transmission
of genetic
information.
DNA spills from E. coli cell.
Function of DNA
Modern Biology
Pages 193 - 195
Genetic
information
must tell
cell(s) how to
make
proteins.
Proteins are made in the cytoplasm
but DNA remains in nucleus
Functions of DNA
Modern Biology
Pages 193 - 195
Proteins
form
structures
and control
chemistry
of cell.
Ribosomes embedded in the E.R.
construct proteins
Functions of DNA
Structure
of DNA
must allow
exact
replication
to occur.
Modern Biology
Pages 193 - 195
Why Understanding
DNA is Important to
You.
DISCOVERY OF
DNA – GRIFFITH’S
EXPERIMENT
• Called
transformation.
• Used mice and
pneumonia.
– Rough (non-virulent)
– Smooth (virulent)
Griffith’s
Experiment
Modern Biology
Pages 193 - 195
Avery Determines DNA To
Be Hereditary Molecule
• Avery,
McCloud,
and McCarty
– Used process
of elimination.
– Determined
DNA was
heredity
material.
Modern Biology
Pages 193 - 195
Important People in
DNA Science
Modern Biology
Pages 184 - 187
• Rosalind
Franklin of Cal
Tech in Los
Angeles took
pictures using
X-Rays in the
1930’s
Was never given due credit for her
contribution to DNA Science
Important People in
DNA Science
Modern Biology
Pages 184 - 187
• James Watson
& Francis Crick
discovered
structure of
DNA in 1953.
James Watson Left & Francis Crick right: Nobel
prize for DNA structure
DNA Structure
Modern Biology
Pages 184 - 187
– DNA is a
polymer.
– The
monomer of
DNA is
called a
nucleotide.
deoxyribonucleic acid
Nucleotide
Structure
Modern Biology
Pages 184 - 187
• One 5 carbon
sugar called
deoxyribose.
– “Deoxy” = one less
oxygen.
– “ribo” = than
ribose.
• Deoxyribonucleic
acid
– “nucleic” = found in
nucleus.
– “acid” = acidic
Deoxyribose, a pentose sugar, has
each carbon numbered.
Nucleotide
Structure
Modern Biology
Pages 184 - 187
Phosphate group
attached to the
#5 carbon of the
sugar.
The phosphoric acid
is negative and so
makes the DNA
molecule negative.
The deoxyribose has a nitorgenous base and a
phoshate attached to it.
Nucleotide
Structure
Modern Biology
Pages 187 - 189
One nitrogenous base
attached to the #1
carbon in the sugar..
–Adenine (Purine)
–Guanine (Purine)
–Cytosine (Pyrimidine)
–Thymine (Pyrimidine)
Four bases of DNA
DNA Structure
• DNA
molecule has
shape of a
double helix.
• The sides are
anti-parallel.
Modern Biology
Pages 187 - 189
DNA Structure
Modern Biology
Pages 187 - 189
• Nucleotides
linked together
form the sides
of the DNA
molecule.
• Phosphodiester
bond links
phosphates and
deoxyribose
Each phosphate is linked to
two sugar molecules.
DNA Structure
Modern Biology
Pages 187 - 189
Complementary base pairing
rules
– Nitrogenous bases form “steps” or
rungs of the helix.
• Adenine (2 rings) is bonded with
Thymine (1 ring) using 2 hydrogen
bonds.
• Guanine (2 rings) is bonded with
Cytosine (1 ring) using 3 hydrogen
bonds.
CENTRAL DOGMA
OF DNA
DNA
mRNA
Modern Biology
Pages 187 - 189
Protein
1) DNA must send a message to ribosomes as to how a
protein is to be produced.
2) DNA must replicate itself exactly prior to each cell
division.
Replication of
DNA
• Replication must:
– Occur prior to
every cell division.
– Occur during “S”
phase of
interphase.
– Result in two
identical copies of
the DNA molecule.
Modern Biology
Pages 187 - 189
Replication of
DNA
• DNA replication
is semiconservative
– Each new
molecule is
composed of one
old and one new
strand.
Modern Biology
Pages 187 - 189
Modern Biology
Pages 187 - 189
Replication
Process
• Replication fork is
where double helix is
split apart.
• Double helix is split
apart by enzyme
called DNA Helicase.
Modern Biology
Pages 187 - 189
Replication Process
• Role of DNA
polymerase.
– Constructs a new
strand of DNA
• One side is
continuous
• One side is
discontinuous
• Complementary
nature of bases
allows replication to
occur properly.
• Replication occurs at
many sites at same
time.
Modern Biology
Pages 187 - 189
Modern Biology
Replication
Process
Pages 187 - 189
•Mistakes and repair processes.
–Xeroderma Pigmentosa
–Lacks proper enzyme to repair DNA
damage due to sunlight.
•Multiple carcinomas
develop due to exposure
to uV light
RNA
Modern Biology
Pages 190 - 194
•Structure of RNA.
–Ribose instead of
deoxyribose.
–Uracil instead of thymine.
–Single helix instead of
double.
•Three types of RNA.
–mRNA
–tRNA
–rRNA
RNA is made from DNA
TRANSCRIPTION
Modern Biology
Pages 190 - 194
• Making mRNA
as a messenger.
– Process
referred to as
transcription.
– Purpose is to
copy the
message for a
protein from
the DNA
molecule.
Making mRNA
TRANSCRIPTION
Modern Biology
Pages 190 - 194
• Transcription
– DNA untwists and
unzips in area of
molecule where the
message for a certain
protein is held.
– Role of RNA
polymerase.
– Role of promoter.
– Role of termination
signal.
Making mRNA
TRANSCRIPTION
– The product of
transcription is
mRNA,
tRNA,and
rRNA.
– Transcription
occurs in the
nucleus of the
cell.
Modern Biology
Pages 190 - 194
Translation
Modern Biology
Pages 190 - 194
• Translation occurs in the
cytoplasm.
• Amino acids are
assembled polypeptides.
(Proteins)
• Ribosomes assemble
polypeptides based on
instructions held in the
DNA molecule.
mRNA leaving the nucleus
Translation
Wednesday 1/8/03
Pages 194 - 198
• Protein structure
– Composed of building
blocks called amino
acids.
• 20 different types
of amino acids.
• Sequence and length
of amino acid chain
determines the
characteristics of
the protein.
Ribosomes attach to the mRNA
molecule in the cytoplasm.
Genetic code
Wednesday 1/8/03
Pages 194 - 198
• The Genetic Code
• Each 3 nucleotides on
mRNA is a codon.
– Each codon codes
for a specific amino
acid.
– 64 possible codons.
– 1 start codons
– 3 stop codons
– 60 different codons
code for 20
different types of
amino acids.
mRNA codon list
Wednesday 1/8/03
Pages 194 - 198
Translation
Wednesday 1/8/03
Pages 194 - 198
• The ribosome binds to the
mRNA.
• tRNA (with anticodon) brings
proper amino acid to ribosome.
(met tRNA)
• Ribosome moves to next three
bases (codon).
• Another tRNA brings proper
AA to ribosome.
• Protein is assembled.
• Stop codon signals end of
protein.
tRNA brings an amino acid to
the ribosome.