DNA

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KEY CONCEPT DNA structure is the same in all
organisms.
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DNA

• If you unraveled all your chromosomes from all of
  your cells and laid out the DNA end to end, the
  strands would stretch from the Earth to the Moon
  about 6,000 times.

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Lets Review!

• What is a macromolecule?
• What are the four kinds of organic molecules?
• What are nucleic acids made of?

- A large organic molecule (made of carbon!)
- Carbohydrates, lipids, proteins and nucleic
acids
- NUCLEOTIDES Phosphate group, 5-carbon sugar,
nitrogenous base
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Nucleic Acids

• Nucleic Acids are the chemical link between
  generations dating back to the beginning of life
  on earth.
•  

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Nucleic Acids

• A nucleic acid is a complex macromolecule that
  stores information in cells in the form of a
  code.

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DNA

• What are genes made of?
• Where are genes located?
• How do they determine characteristics?

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Try to figure out what happened?

• Harmless Disease-causing Heat-killed
  Harmless Heat-
• bacteria bacteria disease causing killed
  disease causing

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Figure 122 Griffiths Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough colonies)
Control(no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth
colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causingbacteria (smooth colonies)
Go to Section
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Figure 122 Griffiths Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough colonies)
Control(no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth
colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causingbacteria (smooth colonies)
Go to Section
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Some History

• While Frederick Griffith was experimenting with
  pneumonia, he discovered that mice injected with
  dead bacteria still died of pneumonia so it was
  something inside the bacteria that was still
  passed on to the next generation.
• Oswald Avery and other scientists discovered that
  DNA is the nucleic acid that stores and transmits
  the genetic information from one generation of an
  organism to the next.

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Some More History

• Alfred Hershey and Martha Chase concluded that
  the genetic material of the bacteriophage (a
  virus that eats bacteria) is DNA, not protein.

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Figure 124 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Go to Section
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Figure 124 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Go to Section
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Figure 124 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Go to Section
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DNA

• Genes are made of DNA deoxyribonucleic acid
• How could DNA code for everything genes do?
• Genes had to carry information from one
  generation to the next
• Genes had to put that information to work by
  determining the inheritable characteristics of
  organisms
• Genes had to be easily copied, because it is
  replicated every time the cell divides

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DNA Structure

• Double Helix
• (twisting ladder)
• modeled by Watson Crick 1953
• Sides/backbone - alternating deoxyribose sugar
  phosphate
• Rungs - nitrogen bases held together by
  hydrogen bonds

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The Double Helix

• Rosaline Franklins x-ray showed that two DNA
  strands are twisted around each other.
• James Watson and Francis Crick used Franklins
  x-ray to make a model of DNA.
• Watson and Cricks model of DNA was a double
  helix, in which two strands were wound around
  each other.
• Watson and Crick also discovered that hydrogen
  bonding held the nitrogenous bases together.

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DNA

• DNA DeoxyriboNucleic Acid
• Short nucleic acid
• A polymer that stores genetic information
• Found in the chromosomes of all organisms
• Controls production of proteins depending on
  sequence of nitrogen bases
• Unit of structure nucleotide

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DNA

• Nucleotide 3 parts
• A phosphate group PO4
• A 5 carbon sugar deoxyribose
• A nitrogen base

Draw the Picture
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Base Pairing

• Base Pairing According to Chargaffs Rule
• The complementary bases always pair a certain
  purine with a certain pyrimidine

• Base
• A adenine
• T thymine
• C cytosine
• G guanine

Complementary Base thymine adenine
guanine cytosine
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Base Pairing Rule

• A always pairs with T
• C always pairs with G

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Nitrogen Bases

• Nitrogen Bases name source for the nucleotides
• 2 different types
• Purines double ring
• Adenine
• Guanine
• Pyrimidines single ring
• Cytosine
• Thymine

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Nitrogen Bases
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DNA Structure
Phosphate Group
Deoxyribose Sugar
Nitrogenous Base
Weak Hydrogen Bonds
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Figure 127 Structure of DNA
Section 12-1
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key Adenine (A) Thymine (T) Cytosine (C) Guanine
(G)
Go to Section
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Lets pair up DNA!

• What would pair up with ATCG?
• TAGC
• What would pair up with ATTAGC?
• TAATCG
• What would pair up with ATACGGTC?
• TATGCCAG

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Replication General Info

• The exact copying of DNA
• DNA must be copied before cells divide ? each
  daughter cell has a complete set of DNA
• Original strands serve as templates for new
  strands
• Replication occurs in both directions

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Replication General Info

• How it happens
• Helicase (enzyme) unwinds the DNA by breaking
  hydrogen bonds

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• 2. DNA polymerase (enzyme) joins individual
  nucleotides to each separated strand, producing
  DNA molecule
• DNA polymerase also proofreads each new DNA
  strand to make perfect copies

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Results of Replication

• 2 DNA molecules ? each contains one original
• strand one new strand (semi-conservative)

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Review of The Genetic Code

• The sequence of nitrogen bases (A,T,C G) along
  a DNA strand code for the synthesis (making) of
  specific proteins.
• According to Chargaffs Rule
• A bonds with T
• C bonds with G

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What are chromosomes???
Nucleotides make up DNA DNA winds into
Chromatin Chromatin condenses into
Chromosomes Chromosomes contain Genes Genes are
sections of DNA THAT CODE FOR PROTEINS Chromosome
s contain Instructions for making YOU!!!
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• Proteins are made in the ribosomes outside the
  nucleus.
• DNA is copied (replicated) in the nucleus but
  cannot leave the nucleus.
• THEREFORE.

• A message must be sent to the ribosomes in the
  cytoplasm telling them what proteins to make.
• This message is carried by a nucleic acid called
  messenger (mRNA ).

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RNA Structure
RNA differs from DNA in 4 ways

1. RNA is a single strand
2. RNA has the sugar ribose
3. Adenine bonds with Uracil (NOT thymine).
4. Can leave the nucleus

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Differences Between

• DNA
• Deoxyribose Sugar
• Double Stranded
• A, C, T, G
• Remains in nucleus

• RNA
• Ribose sugar
• Single Stranded
• A, C, U, G
• Moves out of nucleus

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• Lets wrap it up with a few questions together

1. How many strands does DNA have?
a. one
b. two
c. three
d. four
2. Which scientists came up with the double helix
model of DNA?
a. Hershey Chase
b. Watson and Crick
d. Darwin Malthus
c. Galileo Aristotle
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3. What holds the strands of DNA together?
a. Phosphate Group
b. Deoxyribose Sugar
c. Hydrogen Bonds
d. Nitrogen bonds
4. What DNA bases would pair up with CATTAT?
a. CATTAT
b. TATTAC
c. GTAATA
d. GUAAUA
5. What DNA bases would pair up with GAATCC?
a. CTTAGG
b. GAATCC
d. GCCTCC
c. CGGAGG
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Is your answer the same as earlier

• What are genes made of?