Molecular Biology of the Gene

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Chapter 9

• Molecular Biology of the Gene

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Bacteriophages
Bacteriophages are viruses that eat bacteria.
They were used to identify where genetic material
is located
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Hershey-Chase Experiment
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DNA Structure
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Nitrogenous Bases of DNA
The nitrogenous bases give the nucleotides their
properties and information
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RNA Nucleotide
RNA uses the same nitrogenous bases as DNA with
one exception Instead of Thymine, RNA uses
Uracil in its place
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The Double Helix
This rope ladder model depicts how strands of DNA
are twisted together
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DNA Models
DNA forms the shape of the twisted rope ladder,
the double helix, while maintaining the internal
structure of the nucleotides
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DNA Replication
To replicate, DNA splits open and a copy of each
side is made, attaching itself to the appropriate
partner strand
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Gene Expression
Transcription is the process by which RNA is
produced based on the information in
DNA Translation is the process by which proteins
are made from amino acids based on the
information in RNA
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Transcription and Translation
The gene is the information needed to produce a
protein Three base pairs make up the codon,
which is the information needed to install an
amino acid Stringing amino acids together makes
a protein
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Genetic Code
Lining up three base pairs forms a codon, which
instructs the ribosome to bring in a certain
amino acid The codon forms the foundation of the
genetic code Multiple codons make up the gene
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Mutations
Mutations are formed when one or more nucleotides
are replaced with wrong nucleotides
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Viruses Reproduction
Viruses reproduce by incorporating their DNA into
the DNA of a host
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Plant Viruses
This rod-shaped virus causes the tobacco mosaic
virus in tobacco plants Most plant viruses have
RNA and not DNA
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Enveloped Viruses
Many animal viruses are enveloped in
proteins These proteins are the way that the
immune system recognizes that the virus is not
part of the organism and decides to develop
antibodies to fight the virus
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HIV
Human Immunodeficiency Virus the AIDS virus
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HIV
HIV is called a retrovirus because it reproduces
by turning its RNA into DNA and incorporating
itself into the DNA of the cell
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Summary

• DNA as genetic material
• DNA Replication
• The Genetic Code nucleotides, codons, genes
• Transcription
• Translation
• Viruses