DNA

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DNA
Chapter 12 Section 1
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DNA
Deoxyribose Nucleic Acid The Architect of Life
The First three-dimensional xerox
machine
Life Instruction Manual
The Molecule of Heredity
The Blueprint of Life
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DNA
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Why Study DNA?

• To truly understand genetics, biologists first
  had to discover the chemical structure of the
  gene
• This would then help them understand how genes
  control the inherited characteristics of living
  things
• Gene expression is what enables cells of the
  same organism to take on so many different
  sizes, shapes and functions
• (even though just about every cell in an
  individual contains the same DNA)

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Review

• What organelle is known as the control
  center of the cell?
• What structures are found in the nucleus?
• What are short segments of chromosomes?
• 4. What are genes/chromosomes composed of?
• 5. How do genes/chromosomes control the
  activity of the cell?

nucleus
chromosomes
genes
DNA
produce
proteins thatregulate cell functions and become
cell structures
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Review
Review
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History

• 1869 - Friedrich Miescher discovered DNA in
  nucleus
• 1928 - Frederick Griffith Identified DNA as
  source of genetic material using
  bacteria
• 1930s - Oswald Avery, Colin MacLeod and Maclyn
  McCarty - Confirmed that genes made
  of DNA
• 1950 - Alfred Hershey and Martha Chase confirmed
  DNA is the biochemical of heredity
  using radioactive markers
  bacteriophages
• 1952- Maurice Wilkins and Rosalind Franklin
  X-rayed DNA to show repeating
  nucleotide structure
• 1953- James Watson and Francis Crick combined
  data to create a 3-D model of
  structure called the double helix

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Watson-Crick Model
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DNA Structure

• Is a polymer of 1000s of nucleotide monomers
• Is a double strand of covalently bonded
  nucleotides in twisted ladder shape
• twisted ladder shape double helix

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DNA Shape
Double helix 2 spirals wound around each
other
But joined in the middle
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DNA Structure

• Is a polymer of 1000s of nucleotide monomers
• Is a double strand of covalently bonded
  nucleotides in twisted ladder shape twisted
  ladder shape double helix
• Rungs of ladder nitrogen bases
• Sides of ladder sugar phosphate groups
  (also called the DNA backbone)

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Nucleotide

• Nucleotide- Individual unit of DNA.
• Made of three parts
• Deoxyribose (5-carbon sugar)
• Phosphate group
• A nitrogen-containing base

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Bases

• Four nitrogen-containing bases
• Adenine
• Guanine
• Cytosine
• Thymine

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Bases

• Adenine
• double ringed
• Guanine
• Thymine
• single ringed
• Cytosine

purines
pyrimidines
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Nucleotide
Deoxyribose (like ribose)
is a sugar with 5 carbon  atoms
in a ring Oxygen is one of the ring members
In Deoxyribose, one of the OH groups is missing
and replaced with hydrogen Thus deoxy
- 1 oxygen
H
OH
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Nucleotide
P - the Phosphate group Is important because it
links the sugar on one nucleotide with the
phosphate of the next nucleotide to make a
polynucleotide Nucleotides are connected to each
other via a covalent bond
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Base Pairing Rule

• Bases are paired together in specific manner
• Because of chemical structure and shape
• Adenine only pairs with Thymine
• Guanine only pairs with Cytosine
• Exactly enough room for only one purine and
  one pyramide base between the two strands of
  DNA

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Base Pairing Rule

• Bases held together in rungs by weak hydrogen
  bonds
• 2 hydrogen bonds between A T
• 3 hydrogen bonds between C G

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DNA
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DNA Function

• Scientists wondered how DNA worked.
• They knew genes do these critical things
• Carry information from one generation to
  another
• Put information to work to determine an
  organisms characteristics
• Can be easily copied
• Store and transmit genetic information
  needed for all cell functions
• In order to do these things it had to be a
  special molecule!

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Understanding DNA

• Our knowledge of DNA put to use
• Inheritance/ Genetic Counseling
• Cell function/protein synthesis
• Embryonic development/gene regulation
• Evolution/ phylogenetic relationships
• Medicine/genetic diseases
• Genetic engineering/ recombinant DNA

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Structure of DNA Review
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key Adenine (A) Thymine (T) Cytosine (C) Guanine
(G)
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Structure of DNA Review
Pyrimidines
Purines
Adenine
Guanine
Cytosine
Thymine
Bases
Phosphate group
Deoxyribose
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DNAs Size
To get an idea of the size of the human genome
present in each of our cells, consider the
followinganalogy If the DNA sequence of the
human genome were compiled in books, the
equivalent of 200 volumes the size of a
Manhattan telephonebook (at 1,000 pages each)
would be needed tohold it all. It would take
about 9.5 years to read out loud (without
stopping) the 3 billion bases in one person's
genome sequence, calculated on a reading rate of
10 bases per second, equaling 600 bases/minute,
36,000 bases/hour, 864,000 bases/day,
315,360,000 bases/year.
Human Genome Project
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(No Transcript)
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Structure of DNA Review
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T
A
DNA
C
How Am I Packaged?
G

• Nitrogen bases
• 1. Are like letters in the code
• 2. Put them in different order make
  a different gene

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A
DNA
Package

• Genes
• 1. Are like words made up of letters
• 2. A group of nitrogen bases that
  makes sense
• 3. Tells the cell to do something

T
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The cat sat.
One dog ate.
DNA
Package
The big hat.

• DNA strand
• 1. Are like sentences made up of words
• 2. A long line of genes on each DNA
  strand

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DNA
Package

• Chromosomes
• 1. Are like books full of sentences
• 2. DNA strand twists around and
  around itself

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DNA
Package

• Nucleus
• 1. Is like a bookcase
• 2. Inside the cell, where all the
  chromosomes are stored

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DNA
Package

• So what would a library full of rows and rows
  of bookcases represent?
• many cells together
• which is a tissue