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DNA
The Blue Prints of Life!
What do you think is the purpose
of DNA ...why does it exist at all?
Is DNA found in all creatures?
How different is DNA among
different creatures? A dog? A
banana? A bacterium?
If the total DNA in one
person were laid in a
straight line, it would
stretch to the sun and back
over 600 times (it's 93
million miles from here to
the sun).
You could fit one million
threads of DNA across
the period at the end of a
sentence.
Modern Humans have about 1 – 4 %
Neanderthal DNA.
The difference between your DNA and
the person next to you is less than
0.1%.
You share about 96% of your DNA with
a Chimpanzee, our closest relative on
planet Earth.
You share about 60% of your DNA with
a Banana.
What is DNA?
• DNA (De-oxy-ribo-nucleic Acid) is the
nucleic acid that stores the genetic code.
What is a Genetic Code?
• Genetic Codes are programs of the cell. In other
words how cells store information they pass from
one generation to the next.
WHAT IS DNA MADE OF?
•
DNA is a polymer (Large Molecule)
formed from units called nucleotides.
– A nucleotide is made up of three parts:
1. Nitrogen base
2. Deoxyribose (5 carbon sugar)
3. Phosphate group
NITROGEN BASES
• There are 4 different nitrogen bases:
• Adenine (A) and Guanine (G) which are
the purines
• Cytosine (C) and Thymine (T) which are
the pyrimidines
BASE PAIRING RULES
• Erwin Chargaff discovered the base pair
ruling that in DNA:
– Adenine (A) pairs with Thymine (T) by 2 hydrogen bonds
– Cytosine (C) pairs with Guanine (G) by 3 hydrogen bonds
REMEMBER
• AT and GC
– OR ELSE!!!!!
Testing Your Skill
Can you write the corresponding Nitrogen Base?
1. GAC TAT ATT GAC ATT GAG CCC TTA
2. ATA GAG CAC GCA TAT CCG AGT TAT
Do you understand how to match up the bases???
IF NOT ASK FOR HELP NOW!!!
STRUCTURE OF DNA:
• Is called a double helix (resembles a twisted
ladder): has 2 strands
Watson and Crick
• Made the first model of the DNA ladder called
the Double Helix in 1953.
• They used X-ray crystalography pictures created
by Rosalind Franklin and Chargaff’s rule to
develop their ladder.
• They won the nobel prize in 1962 for their
accomplishments.
ROSALIND FRANKLIN
• Rosalind Franklin also
played a major role in the
ladder’s discovery because
Watson and Crick used her
photos of the DNA ladder to
figure out and assemble the
model. (Unfortunately she died 4
years before the nobel prize was
awarded at the age of 37 of
ovarian cancer. Her contributions
were made known later after the
award was given. According to
Nobel Prize Rules, the individual
must be alive in order to receive
the award )
History of
DNA
(CONT)
1. Fredrick Griffith (microbiology research with nucleic acids)
2. Oswald Avery (colleague that completed/supported Griffith’s work)
3. Alfred Hershey and Martha Chase (proved that DNA and
not protein is the genetic material of life)
4. Erwin Chargaff (A-T, G-C)
5. Rosalind Franklin (x-ray pics-DNA)
6. Francis Crick and James Watson (double helix model)
Born: London, England, July 25, 1920
Died: London, England, April 16, 1958
Pioneer Molecular Biologist
There is probably no other woman
scientist with as much controversy
surrounding her life and work as
Rosalind Franklin. Franklin was
responsible for much of the research
and discovery work that led to the
understanding of the structure of
deoxyribonucleic acid, DNA.
DNA Replication (synthesis)
DNA replication is an important process because as cell divide, it is
critical that the two daughter cell are identical to the original cell.
Now we will look at how DNA replication take place.
Process of DNA Replication
1.
Each strand (side) of DNA serves as a
template for a new strand of DNA
2. Steps of replication:
a) Enzymes unzip DNA breaking hydrogen
bonds between bases.
b) The two strands unwind.
c) Each DNA strand serves as a template
for complementary bases.
Example: TEMPLATE DNA: TAC-GTT
NEW DNA: ATG-CAA
d) DNA replicates itself exactly so that each
new cell will have an identical copy of
the original DNA ladder.
DNA REPLICATION VIDEO
REPLICATION VIDEO (ADVANCED)
RNA
There are 3
different types:
1.mRNA
2.tRNA
3.rRNA
mRNA
• mRNA is the nucleic acid that
acts as a messenger between
DNA and ribosomes and carries
the genetic code for making
protein from amino acids.
mRNA
Just like DNA, RNA is made of
Nucleotides: A, U, C, G.
Notice, RNA does not contain
thyamine (T) as a base, but
instead has uracil (U).
So in RNA its AU and CG
PROTEIN SYNTHESIS
Why make protein?
Proteins are needed for cell structure and
movement, makes enzymes and nucleotides.
TRANSCRIPTION
• Transcription is the process
in which a molecule of DNA
is copied into a
complementary strand of
RNA.
– DNA is in the nucleus and can’t
leave, so a messenger RNA(mRNA) must bring the genetic
information from the nucleus to
the ribosomes in the cytoplasm
Steps in Transcription
1. RNA polymerase attaches to
DNA and moves along it
unwinding the two strands
2. RNA nucleotides match up
with the bases of DNA
Ex: DNA TGCACGCA
mRNAACGUGCGU
CODONS
• Codon- is a 3 letter word composed of 3
nucleotides on mRNA.
– Each codon codes for a particular amino acid while
chains of amino acids form proteins.
– There are 64 different codons; there can be more
than 1 codon for each amino acid.
– There are start and stop codons.
EXAMPLES OF CODONS
AUG-CCC-GAA-GGG-UAA
CAN YOU IDENTIFY THE CODONS IN THE
PROBLEMS BELOW?
1. AUGCCCAUAGACUAG
2. AUGGACCGGCUUUAA
YOUR TEACHER WILL TEACH YOU HOW TO USE THE CODON TO
IDENTIFY THE AMINO ACID
PROTEIN SYNTHESIS VIDEO
STILL CONFUSED?
• Imagine that you are a mechanic. The repair
manual that you use is the DNA ladder.
• If you wanted to copy the instructions to install
a radio in your car, would you copy the entire
repair manual? (RAISE YOUR HAND TO ANSWER)
• NO!!! You would only copy the portion
pertaining to installing the radio. That is what
transcription does.
CONTINUED
• Enzymes open the DNA ladder and the needed
portion is copied in the form of mRNA.
• Why is it called mRNA?
It carries the message or instructions on how to
assemble something.
• What’s next?
This message is carried from the nucleus to a
ribosome which is located outside of the
nucleus.
(HINT: M=Messenger)
translation
• is the process of building a
protein molecule according
to code in mRNA.
Translation cont.
A. During the process, transfer
RNA (tRNA) carries amino
acids to ribosomes where the
amino acids are joined to
form the protein.
(**ribosomes are the place
where protein are made)
Translations cont.
B. Steps of translation:
1. tRNA bind to the mRNA.
2. a “start” codon start the protein
synthesis.
3. tRNA contains 3 complementary
nucleotides to the mRNA called the
anticodon; once it matches it leaves behind
amino acid and next codon is read.
Translation cont.
4. More tRNA molecules will come together
to create the _____________.
5. Once a “stop” codon is read, the new
polypeptide chain is released as a new
protein.
Translation Video