Transcript Genetics: The study of biological information

PowerPoint to accompany
Genetics: From Genes to
Genomes
Fourth Edition
Leland H. Hartwell, Leroy Hood,
Michael L. Goldberg, Ann E. Reynolds,
and Lee M. Silver
Prepared by Mary A. Bedell
University of Georgia
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Introduction to Genetics in the Twenty-First Century
CHAPTER
CHAPTER
Genetics: The study of
biological information
CHAPTER OUTLINE
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1.1 DNA: The Fundamental Information Molecule of Life
1.2 Proteins: The Functional Molecules of Life Processes
1.3 Complex Systems and Molecular Interactions
1.4 Molecular Similarities of all Life-Forms
1.5 The Modular Construction of Genomes
1.6 Modern Genetic Techniques
1.7 Human Genetics
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Three levels of biological information
DNA
• Macromolecule made of nucleic acids
• Repository of the genetic code
Proteins
• Macromolecules made of amino acids
• Amino acid sequence determined by DNA sequence
Biological systems
• Network of interactions between molecules or groups
of cells
• Accomplish coordinated functions
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The biological information in DNA generates
an enormous diversity of living organisms
Fig. 1.1
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Complementary base pairs are a key feature
of the DNA molecule
DNA is comprised of four nitrogenous bases [guanine (G),
adenine (A), cytosine (C), and thymine (T)], a deoxyribose,
and a phosphate
G – C and A – T hydrogen
bonds between each strand
of the double helix
The two strands of the
double helix are in opposite
orientation
Fig. 1.2
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The information in DNA is one-dimensional
and is digital
Biological information is encoded in the nucleotide sequence
of DNA and each unit of information is discrete
DNA sequence can be handled
by computers
• Automated DNA
sequencers can sequence
about 106 base pairs/day
• New technologies can
sequence even more DNA
per day
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Fig. 1.3
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Organization of genetic information in cells
Genes are sequences of DNA that encode
proteins
Chromosomes are organelles that package
and manage the storage, duplication,
expression, and evolution of DNA
Genomes are the entire collection of
chromosomes in each cell of an organism
The human genome:
• 24 kinds of chromosomes
• 3 x 109 base pairs
• Encodes 20,000 – 30,000 genes
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Figure 1.4
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Proteins are polymers of hundreds
to thousands of amino acids
There are 20 different amino acids
Information in DNA of a gene dictates the sequence of
amino acids for the protein
The order of amino acids determines the type of protein and
its three dimensional structure
Diversity of three-dimensional structure of protein
generates an extraordinary diversity of protein function
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The amino acid sequence determines
the three-dimensional shape of the protein
Chemical formulas for two
amino acids
Three-dimensional shapes of
two proteins
Figure 1.5a
Figure 1.5c
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Conversion of biological information
from a one- to a four-dimensional state
Fig. 1.6
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Evolution of biological information on earth
RNA may have been the first information-processing
molecule
• Has ability to store, replicate, mutate, express
information, and fold in 3-dimensions
• RNA is unstable so other stable macromolecules
evolved
DNA took over the linear information and replication
functions
Proteins took over the 3-dimensional folding functions
All organisms alive now descended from the first organisms
that adopted this molecular specialization
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RNA evolved into an intermediary in
conversion of DNA information into protein
RNA is comprised of four nitrogenous bases [guanine (G),
adenine (A), cytosine (C), and uracil (U)], a ribose, and a
phosphate
Bases are read as triplets to encode amino acid subunits of
protein
Fig 1.7a
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All living organisms use
essentially the same genetic code
Specific triplets of
RNA bases encode
the 20 amino acids
Figure 1.7b
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Many genes have similar functions
in different organisms
Comparison of gene products in different organisms can
reveal identical and similar amino acid sequences
e.g. cytochrome C protein from six species
Figure 1.8
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A gene from one organism can functionally
replace a gene in another organism
Example: Pax6
gene is required for
eye development
in insects, mice,
and humans
Expression of
human Pax6 gene
in Drosophila can
induce eye
development
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Figure 1.9
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Fossil evidence for some of the major stages
in the evolution of life
Duplication and divergence of genetic information is
evident in the evolutionary history of life
Table 1.1
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The modular construction of genomes
Hierarchical organization of information in chromosomes
In eukaryotes, exons are arranged into genes
• Exons from different genes can be rearranged to create
new combinations
Genes can duplicate and diverge to create multi-gene
families
• Multi-gene families can rapidly expand to create superfamilies
Regulatory networks that control gene expression can
change rapidly
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Evolution of gene families by duplication
of ancestral genes
Gene duplication followed by sequence divergence
underlies the evolution of new genes with new functions
Figure 1.10
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Example of the effects of changes
to a key regulatory network
Two-winged flies evolved from
four-winged flies
This evolutionary change was
also accomplished in the lab
 Mutation of a regulatory
network converts a normal
two-winged fly into a fourwinged fly
Figure 1.11
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Modern genetic techniques
Genetic dissection of model organisms
• Inactivate a gene and observe the consequences
Genome sequencing
• Human Genome Project
• Model organisms and other organisms
Understanding higher-order processes that arise from
interacting biological networks
Genomics can rapidly analyze thousands of genes
• High-throughput DNA sequencing and genotyping
• Large-scale DNA arrays (chips)
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Genomes of five model organisms
were sequenced as part of the
Human Genome Project
Figure 1.12
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New global tools of genomics can analyze
thousands of genes rapidly
Schematic drawing of the components of a DNA chip
Figure 1.13a
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Hybridization of cDNAs made
from cellular mRNAs to a DNA chip
Figure 1.13b
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Computerized analysis of chip hybridizations
can be used to compare mRNA expression
in two types of cells
Thousands of genes can be simultaneously analyzed
In this example, genes whose expression was altered by
treatment with an experimental cancer drug were identified
using a DNA chip
Figure 1.13c
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The focus of this book is on human genetics
Genetics has powerful tools for understanding human
biology
Paradigm shift from studying one gene or protein at a time
to studying interacting networks of many genes and
proteins
Molecular studies can lead to predictive and preventive
medicine
• DNA diagnostics can be used to generate a genetic
profile of an individual
• Design of therapeutic drugs to prevent or minimize
symptoms of gene-based diseases
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Important implications of genetics to
social issues
Entire genetic profiles of individuals will become available
This genetic information can be used to help people
• Make predictions about future possibilities and risks
Or, genetic information could also be used to to restrict
people's lives
• Genetic Information Nondiscrimination Act was passed
by the federal government in 2008
 Prohibits discrimination on the basis of genetic tests by
insurance companies and employers
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Important implications of genetics to
social issues (continued)
Proper interpretation of genetic information and
understanding of statistical concepts is essential
Regulation and control of new technology
• Transgenic technology (genetic engineering) is routine
in many animals
• Should genetic engineering of human embryos be
allowed?
Guidelines must be established to prevent misuse of new
knowledge in human genetics
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