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Genetics
The Study of Biological
Information
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Chapter Outline
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DNA molecules encode the biological information
fundamental to all life forms
Proteins are the primary unit of biological function
Regulatory networks specify the behavior of genes
All living forms are closely related
Genomes are modular, allowing rapid evolution
Genetic techniques permit dissection of biological
complexity
Focus of this course is on human genetics
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Information in DNA generates
diversity
Fig. 1.1a
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Four bases – G (guanine), A
(adenine), T (thymine), and C
(cytosine) are the nucleotide
building block of DNA
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DNA is a double stranded helix
composed of A-T and G-C
complementary bases
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Order of nucleotide sequences
determine which proteins are
synthesized, as well as when and
where they the synthesis occurs.
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Genetic Information is Digital
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Fig. 1.3
The sequence of bases
in DNA can be read by
DNA sequencers, stored
in computers, and
synthesized by DNA
synthesizers
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Genes are sequences of DNA that
encode proteins
Fig. 1.2
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DNA resides in within cells packaged
as units called chromosomes
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Fig. 1.4
The entire collection of
chromosomes in each cell
of an organism is called a
genome
Human cells have 24
distinct kinds of
chromosomes
The human genome has
about 3 x 109 base pairs
and 20,000 – 30,000 genes
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Biological function emerges primarily
from proteins.
Amino acids have a basic amino group (-NH) and an acidic carboxyl group (-COOH)
Alanine has a relatively simple CH
side chain
Tyrosine has a more complex aromatic side
chain
Figure 1.5a
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A comparison of equivalent chains
of two digestive proteins
Figure 1.5b
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The diversity of protein structure
generates extraordinary diversity
Fig. 1.5b
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Proteins are polymers of
amino acids
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Proteins have three dimensional structures
Information in DNA dictates the sequence
of its amino acids
There are 20 different amino acids
The order of amino acids determines the
type of protein and its structure
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Proteins interact with DNA and
other proteins
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Biological systems function as complex
interactive networks of proteins and DNA
that interact with one another
Fig. 1.6
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All living things are closely related
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Fig. 1.7a
RNA was probably the first informationprocessing molecule
RNA is composed of four bases: guanine
(g), adenine (a), cytosine (c), and uracil (u)
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All living organisms use the same
arbitrary codes for RNA, DNA, and
protein
Fig. 1.7b
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Many genes have similar functions in
very different organisms
Fig. 1.8
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Relatedness among organisms is
important for the study of human
genes
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Studies of genetics in model organisms help
us understand how genes work in humans
Some model organisms include bacteria,
yeast, roundworms, fruit flies, and mice.
Model organisms may have simpler
biological networks and can be manipulated
experimentally.
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Modular construction of genomes
has allowed rapid evolution of
complexity
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Gene families arise from primordial genes
through duplication and rearrangements
Duplication followed by mutations
rearrangements can generate new genes
with new functions
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The process of duplication and
divergence
Fig. 1.10
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Duplication and divergence has
made rapid evolution possible.
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Rapid change in regulatory networks
specify how genes behave
Fig. 1.9
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Genetic techniques permit the dissection
of complexity
Genes can be identified and inactivated one
at a time using genetic techniques
 Dissection of genomes gene-by-gene
unravels the complexity of biological
systems
 The challenge for modern biology lies in
understanding how the multitude of
networks of genes and higher level systems
interact to produce complex systems.
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Genome sequencing projects are a
step in understanding the complexity
of genomes
Fig.1.12
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New technological tools facilitate the
dissection of genomes and integration
of information
DNA chips detect the expression of thousands of genes in
response to environmental changes
Fig. 1.13c
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Focus on human genetic
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Genetics is a field of science that will have
an enormous impact on society
Our understanding of biological complexity
using genetic approaches is proceeding at a
very rapid pace
Recent technological advances have shifted
the focus of genetics from analysis of single
genes and proteins to entire networks – the
Systems Approach
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Genetics
Predictive and Preventative Medicine
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Discovery of genes with variations that cause
or predispose one to disease will continue at
a rapid pace.
Gene therapy
 Diagnostics
 Therapeutic drugs to block or reverse effects of
mutant genes
 Detection of disease and treatment before onset
may increase life span significantly
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Social issues and genetics
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Should an individual’s genetic profiles be
freely available to insurance companies,
employers, government?
Should our government regulate the use of
genetic and genomic information to reflect
societies social values?
Is it okay to permanently alter genes in
humans for medical or social reasons?
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