Download Nucleic Acids and Protein Synthesis

Nucleic Acids and
Protein Synthesis
I. DNA= deoxyribonucleic acid
A. Contains Genes = specific locations on DNA.
1. Genes specify proteins and traits (eye color, disease, etc)
DNA is bundled into structures called
chromosomes.
• If the DNA in a person was stretched out it would
reach to the sun and back 600 times. It is an
extremely long molecule that coils really tight.
B. The Structure of DNA
1. Rosalind Franklin and Maurice Wilkins
a) Produced X-ray diffraction photograph
of DNA.
b) Showed that: DNA is a double helix.
2. James Watson and Francis Crick (1953)
a) Used Franklin’s info to build DNA model
b) Model= double helix of repeating nucleotide monomers
`
1953
2003
c. Nucleotides have three parts:
1) Deoxyribose Sugar
2) Phosphate Group
3) Nitrogen Base (4 kinds)
Purines = Adenine (A) & Guanine (G)
Pyrimidines = Thymine (T) & Cytosine (C)
How do the nitrogen bases
bind?
d.Sugar-phosphate
molecules on outside of
ladder; paired bases on
inside.
e.Purines paired to
pyrimidines.
1) A is hydrogen-bonded to T
2) G is hydrogen-bonded to C
f. Watson and Crick
- Nobel Prize in 1954 for
their model of DNA.
Stop
End of day 1
II. DNA Replication
= process of duplicating a molecule of DNA
A.Begins at a specific
sequence of nucleotides
B.DNA is unzipped by DNA
Helicase enzyme.
C.Helicase breaks the
hydrogen bonds between
nitrogen bases.
D.Free floating nucleotides
bind with complementary
bases.
II. DNA Replication
= process of duplicating a molecule of DNA
E. DNA polymerase enzyme
catalyzes the bonding of sugar
and phosphates
F. Results in 2 new strands of DNA
G. Each new DNA molecule has
one old and one new strand
(semi-conservative replication)
H. Special Enzymes (DNA
polymerase) “proofread” and
repair any mistakes
I. If repairs are not made, the
mutations may cause cancer.
I. Replication Errors Do Occur
1. Ability to mutate is requirement for genetic material.
2. Only one error per billion nucleotides.
J. The newly synthesized strand always
forms from 5’ to 3’.
Animation of DNA Replication
• http://207.207.4.198/pub/flash/24/menu.sw
f
• ~ 15 minutes
STOP
End of day 2
III. Ribonucleic Acid (RNA)
A. DNA ultimately determines
amino acid sequence of
proteins.
B. DNA molecule cannot directly
control the sequence of amino
acids.
C. DNA is restricted to nucleus.
D. Go-between is ribonucleic acid
(RNA).
= makes proteins
E.
The Structure of RNA
1. Polymer of nucleotides
(ribose sugar, Nitrogen base, PO 4 group
2. Unlike DNA, RNA :
a) Single-stranded
b) Contains the sugar ribose
c) Contains the nitrogen base
uracil instead of thymine.
No “T” in RNA
A-U
F. There are three major
classes of RNA.
1. Messenger RNA
(mRNA)- takes a
message from DNA in
nucleus to ribosomes in
cytoplasm.
2. Ribosomal RNA
(rRNA)- and proteins
make up ribosomes
where proteins are
synthesized.
3. Transfer RNA (tRNA)transfers a particular
amino acid to a
ribosome.
IV. Central Dogma of
Molecular Biology
A.
B.
DNA undergoes
transcription to mRNA
mRNA undergoes
translation to a protein.
V. Transcription =process in which mRNA is made
according to the sequence of bases in DNA
A. Occurs in the nucleus.
B. Begins when RNA
polymerase (enzyme)
binds to a DNA
molecule. (Unzips the
DNA)
C. Complementary RNA
nucleotides pair with
DNA nucleotides.
D. RNA polymerase joins
the RNA nucleotides
together.
E. Terminator sequence
causes RNA
polymerase to stop.
F. DNA strands rejoin.
VI. Translation
= assembling proteins from “info” encoded in
mRNA
A.Takes place in cytoplasm.
B.One language (nucleic acids)
is translated into another
language (protein).
C.How Genes Code for Amino
Acids
1.DNA serves as a template
to build RNA
2.mRNA contains the
genetic code in the form of
codons.
3. Codons
a) 3 sequential nucleotide bases of
mRNA. (43=64)
b) Each codes for an amino acid.
c) There are 64 triplets to code for 20
amino acids.
d) The Code Is Universal
1) AUG is universal start codon.
2) There are three stop codons.
D.
Ribosome attaches to a
start codon(AUG).
E. tRNA transfers Amino
Acids to the ribosome.
1. tRNA is a singlestranded ribonucleic
acid that doubles back
on itself to create a
cloverleaf structure.
2. At one end it binds to
amino acid; at other
end it has an
anticodon that binds to
mRNA codon.
3. Brings the correct
amino acid to the
codon.
4. Ribosome moves
to next codon and
a new tRNA brings
next amino acid.
5. A peptide bond is
formed between
amino acids.
6. Process continues
until ribosomes hits
a stop codon.
7. Polypeptide
(protein) is formed.