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© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko
PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, and
Campbell Essential Biology with Physiology,
Fourth Edition– Eric J. Simon, Jean L. Dickey, and Jane B. Reece
Chapter 10Chapter 10The Structure and Function of DNA
1 DNA: STRUCTURE AND REPLICATION
• DNA
– was known to be a chemical in cells by the end of the nineteenth century,
– has the capacity to store genetic information, and
– can be copied and passed from generation to generation.
• The discovery of DNA as the hereditary material
ushered in the new field of molecular biology, the
study of heredity at the molecular level.
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Watson and Crick’s Discovery of the Double Helix
• James Watson and Francis Crick determined that
DNA is a double helix.
• Watson and Crick used X-ray crystallography data
to reveal the basic shape of DNA.
• Rosalind Franklin produced the X-ray image of
DNA.
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5 Figure 10.3a
James Watson (left) and Francis Crick
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Figure 10.3b
X-ray images of DNARosalind Franklin
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• The model of DNA is like a rope ladder twisted into
a spiral.
– The ropes at the sides represent the sugar-phosphate backbones.
– Each wooden rung represents a pair of bases connected by hydrogen bonds.
Watson and Crick’s Discovery of the Double Helix
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Figure 10.4
Twist
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• DNA bases pair in a complementary fashion:
– adenine (A) pairs with thymine (T) and
– cytosine (C) pairs with guanine (G).
Watson and Crick’s Discovery of the Double Helix
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Figure 10.5
(c) Computer model(b) Atomic model(a) Ribbon model
Hydrogen bond
11 The Central Dogma of Molecular Biology
• Central dogma of molecular biology
– Formulated by Francis Crick
– Genetic information is transferred within biological system in 3 distinct processes
– Replication
– Transcription
– Translation
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The Central Dogma of Molecular Biology
• Replication
– creating an exact copy. Using nucleotide sequence in DNA to produce another double stranded DNA molecule with the exact same sequences
• Transcription
– Same language and essentially the same words but in a slightly different format. Uses nucleotide sequence in DNA to produce an equivalent nucleotide sequence in an RNA molecule
• Translation
– Converting words from one language into different words in a different
language. Using nucleotide sequence in RNA to produce a sequence of
amino acids in a polypeptide according to specific translation rules. In
essence going from the language of nucleotides to the language of amino
acids.
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Replication Transcription Translation
Template DNA DNA RNA
Polymer synthesized
DNA RNA Polypeptide
Monomernucleotide (deoxyribose)
nucleotide (ribose)
Amino acid
Polymerizing enzyme
DNA polymerase RNA polymerase ribosome
initiation site origin of replication promoterstart site (start codon)
termination site none terminator1 of 3 stop codons
14
DNA and RNA Structure
• DNA and RNA are nucleic acids.
– They consist of chemical units called nucleotides.
– A nucleotide polymer is a polynucleotide.
– Nucleotides are joined by covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar-phosphate backbone.
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15
© 2013 Pearson Education, Inc.
Animation: DNA and RNA Structure
Right click slide / select “Play”
16
Figure 10.1
Sugar-phosphatebackbone
Phosphate
group Nitrogenous base
DNA nucleotide
DNAnucleotide Thymine (T)
Sugar
Polynucleotide
DNAdoublehelix
Sugar
(deoxyribose)
Phosphategroup
Nitrogenous base(can be A, G, C, or T)
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• The sugar in DNA is deoxyribose. Thus, the full
name for DNA is deoxyribonucleic acid.
DNA and RNA Structure
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• The four nucleotides found in DNA differ in their
nitrogenous bases. These bases are
– thymine (T),
– cytosine (C),
– adenine (A), and
– guanine (G).
• RNA has uracil (U) in place of thymine.
DNA and RNA Structure
© 2013 Pearson Education, Inc.
19 Figure 10.2
Sugar(ribose)
Phosphate
Adenine
Uracil
Guanine
Cytosine
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DNA Replication
• When a cell reproduces, a complete copy of the
DNA must pass from one generation to the next.
• Watson and Crick’s model for DNA suggested that
DNA replicates by a template mechanism.
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© 2013 Pearson Education, Inc.
Bioflix Animation: DNA Replication
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Figure 10.6
Parental (old)DNA molecule
Daughter (new) strand
Daughter DNA molecules (double helices)
Parental (old) strand
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• DNA can be damaged by X-rays and ultraviolet
light.
• DNA polymerases
– are enzymes,
– make the covalent bonds between the nucleotides of a new DNA strand, and
– are involved in repairing damaged DNA.
DNA Replication
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• DNA replication ensures that all the body cells in
multicellular organisms carry the same genetic
information.
DNA Replication
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• DNA replication in eukaryotes
– begins at specific sites on a double helix (called origins of replication) and
– proceeds in both directions.
DNA Replication
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Figure 10.7
Origin ofreplication
Origin ofreplication
Origin ofreplication
Parental strands
Parental strand
Daughter strand
Two daughter DNA molecules
Bubble
27 THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN
• DNA provides instructions to
– a cell and
– an organism as a whole.
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How an Organism’s Genotype Determines Its Phenotype
• An organism’s genotype is its genetic makeup, the
sequence of nucleotide bases in DNA.
• The phenotype is the organism’s physical traits,
which arise from the actions of a wide variety of
proteins.
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