Download DNA

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From DNA to Proteins
2 Types of nucleic acid
DNA -> RNA -> Protein
Frederick
Griffith – Experimented with two forms of bacteria
that cause pneumonia on mice
o Smooth (S) and Rough (R)
o Demonstrated Transformation
His
conclusion: some factor changed the bacteria
o “Transforming Principle”

Oswald Avery – Was puzzled by Griffith’s discovery and
worked for 10 years to find the answer.
o Directly observed transformation of R bacteria into S bacteria

Concluded that DNA is the transforming principle
o DNA = Genetic material

Hershey and Chase- supported the conclusion - DNA is the
source of genetic information
o Used bacteriophage infected with radioactive sulfur atoms on
protein.
• Bacteriophage – a virus that infects and replicates within bacteria.
• Minimal radioactivity found in bacteria
o Used bacteriophage infected with radioactive phosphorus atoms on
DNA.
• Radioactivity found in bacteria
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DNA
DNA stands for Deoxyribo Nucleic Acid
DNA is genetic material that determines inherited
characteristics/traits
The job of DNA is to code for proteins in the body.

What is the monomer that makes up DNA?
o DNA is made up of long chains of Nucleotides.
o Nucleotides- make up genes that code for a specific trait.

What makes up a Nucleotide?
o 1. Deoxyribose sugar (
o 2. Phosphate (
o 3. Nitrogen Base
•
•
•
•
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
)
)
Nitrogen bases come in two types:
1. Adenine
2. Guanine
Nitrogen bases come in two types:
Pyrimidines
have ONE
ring
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And come in two
types:
1. Cytosine
2. Thymine
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
Double Helix – Spiral ladder
o Discovered by Watson and Crick in the 1950’s with the help of
Franklin’s x-ray pictures
o Double stranded (Antiparallel)
Complementary base paring – the nitrogen bases on one side of the
ladder ALWAYS pair up with the same nitrogen base on the other side of
5’
3’
the ladder.
o Discovered by Chargaff
o The pairs are held together
with hydrogen bonds
AT
GC
5’
3’
T
P
Complete
the other
side of the
DNA
molecule
P
A
P
P
C
P
P
C
Circle a
nucleotide
P
P
T

How many different types of nucleotides are there? How do they
differ?

What is the monomer of DNA?

What does DNA stand for?

DNA’s shape can be described as a ______________?

What makes up the sides of DNA?

What makes up the rungs?

Remember: DNA is always copied during cell cycle
o Mitosis & Meiosis

This takes place during the S phase of Interphase

1. The DNA molecule is split down the
middle (at the nitrogen bases) by helicase,
breaking the hydrogen bonds.
o Similar to a zipper
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
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2. The nitrogen bases on each side of the
molecule are used as a pattern for a new
strand.
3. Complementary bases are added to
each individual strand by DNA polymerase
(enzyme).
Each new cell can now get a complete copy
of all the DNA. – Semi-conservative
o One of the original strand, one new
DNA
polymerase adds the new
nucleotides one at a time.
Lastly,
DNA ligase enzyme “glues”
nucleotides together on the
lagging strand.
 Both
nucleotide chains separate and serve as a
template for a new nucleotide chain.
 The open structure is often referred to as a
replication fork.
 The leading strand requires fewer steps and
therefore is synthesized more quickly.
 The lagging strand is done in pieces since the helix
uncoiling occurs in the opposite direction the
polymerase is working. These pieces are called
Okazaki fragments.
***You are left with 2 exactly
identical molecules of DNA double
helix.***
Original strands
of DNA
Original
New
New Original
Semi-conservative Model
O
N
N
O
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Original strand: ATTCCG
Complement:
Original strand: GCTAAG
Complementary strand:
Original strand: CTACCA
Complement:
Original:
o Strand A: GACCTA
o Strand B:

What is the purpose of replication?

How does DNA serve as its own template?
new strand
nucleotide
DNA polymerase

DNA  RNA  Protein
Transcription
DNA  RNA
Translation
RNA  Protein
o Why make proteins?
• Skin, muscles, nails, hair,
hormones, enzymes
• How do we make proteins?


RNA is the 2nd type of Nucleic Acid
RNA is made of nucleotides, just like DNA
o 1. Ribose is the sugar
o 2. Phosphate
o 3. Nitrogen Bases
•
•
•
•
Adenine (A)
Guanine (G)
Cytosine (C)
Uracil (U): NOT Thymine (T)
o Single Stranded
o When RNA is assembled based off of DNA’s pattern, this is called
Transcription
Types:
1. mRNA – messenger
2. tRNA – transfer
3. rRNA - ribosomal
Comparing DNA and RNA
DNA
RNA
SUGAR
Deoxyribose
Ribose
BASES
A T C G
A U C G
Double Helix
Single Stranded
Nucleus
Nucleus. Cytoplasm,
Ribosomes
STRUCTURE
LOCATION
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

Occurs in the nucleus
DNA is again unzipped by
RNA Polymerase.
RNA Polymerase adds
complementary RNA nucleotides
DNA is too large to get out of the
nucleus, RNA carries DNA’s message
out of the nucleus to a ribosome.
Ribosome – where the protein will be
made.
o Starting at a region called the promoter
o This makes mRNA
o mRNA = messenger = carries the
message

mRNA leaves the nucleus
DNA
Deoxyribose
P
Deoxyribose
Adenine
---H---
Thymine
Uracil
mRNA
DNA
exits
re-coils
nucleus
RNA
RNAPolymerase
Polymerase
Strands
move
breaks
makes
apart
H-bonds
mRNA
Cytosine
---H---Guanine
Guanine
Guanine
P
Deoxyribose
Ribose
Ribose Deoxy-
ribose
P
P
Ribose
Ribose Deoxy-
ribose
P
P
Thymine
---H---Adenine
Adenine
Adenine
P
P
Ribose
Ribose Deoxy-
ribose
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DNA strand = AATTTGCGCGGCT
mRNA strand =
DNA strand = TATGCGCACTG
mRNA strand =
DNA strand = CGATCAGCCTAT
mRNA strand =
Fill in the missing information
 Many
RNA molecules
require a bit of editing
before they leave the
nucleus.
 Introns- not involved in
coding for proteins
o These get taken out
 Exons-
are expressed


RNA to Protein
Translation converts mRNA messages into Polypeptides
o String of amino acids held together by a peptide bond


A codon is a sequence of three nucleotides that codes for
an amino acid.
Examples:
o AUG= Methionine
o CUU= Leucine

The genetic code matches the mRNA codon with the tRNA
anticodon to link amino acid or action
AUG= Start/ Methionine
UAA, UGA or UAG= Stop

Codon GCA =

Codon AAG =

Codon CGA =
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mRNA carries the DNA instructions for making protein
mRNA goes into the cytoplasm through nuclear pores
mRNA attaches to a ribosome to be “read”
o Ribosomal RNA (rRNA)
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Appropriate amino acids are strung together to build a polypeptide chain
by reading codons.
Amino acids are attached to Transfer RNA (tRNA)
o tRNA is complementary to mRNA
o mRNA codon- ACC
o tRNA anti-codon =
o mRNA codon - GUC
o tRNA anticodon =

Polypeptide chain = protein
MET
MET
ISO
PRO
tRNA
tRNA
tRNA
Start Codon (Methionine)
E Site
UP Site
AA C
This process
continues until a
stop codon is
reached, at which
point the mRNA
strand, tRNA units,
and rRNA subunits
all are released.
UU
AAG UUG
G Site
A
Large Ribosomal Subunit (rRNA)
A G C A A U G A U A C C C
mRNA
A A U A
U
A G
U G
Small Ribosomal Subunit (rRNA)
o Process:
ribosome
mRNA
Codon: 3
nucleotides
of mRNA
A
C
G
C
U
A
U
G
G
U
C
C
G
A
U
G AC
AntiCodon: 3
nucleotides
of tRNA
tRNA
A. A.
Amino
Acid
A. A.
A. A.
TRANSLATION
Process of
assembling
polypeptides
from
information
encoded in
mRNA;
Interpreting
the code!
Number
the 4 anticodons in
the order
they occur
Only
20
Amino
Acids
1
START
codon
3 STOP
codons
1. Which two
mRNA codes
correspond to
histidine?
2. How many
different mRNA
codes
correspond to
arginine?

What are the three parts to the Central Dogma?

How is RNA similar to DNA?
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How is RNA different from DNA?

What are the 3 types of RNA?
There
are two types of mutations
o Sex cell mutations: affect the offspring
o Body cell mutations: affect the individual
only
Lethal mutations vs. beneficial mutations
o Most mutations are good
DNA Polymerase can usually detect errors
 Mistakes
in base paring during DNA Replication
o Cause of many genetic disorders
o Insertions and deletions
 Chemicals:
like tobacco
o Can lead to cancer because it changes the genes that
regulate mitosis
 Radiation:
including UV (sun) and X-ray
o Can lead to cancer because it changes the genes that
regulate mitosis

1. Substitution
o Point where one nitrogen base is substituted for another
o Sickle Cell Anemia: substitute A for T
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2. Deletions and insertions
o When a nitrogen base is deleted or added
o Frame shift mutations- because it moves the
codon up or down
o Changes the sequence of amino acids