Genetics and Biotechnology
World Cultures 120 Presentation
Brian Ernsting
26 March, 2001
Goals
1. To put modern biology in context.
2. To understand a few of the basics of how genes work.
3. To think about the implications of biotechnology.
The ability to understand and manipulate the software of life is
the most important accomplishment of the biological sciences.
Like the revolutions personified by Galileo and Darwin, the
biological revolution changed the way science looks at the
world.
Unlike these revolutions, the twentieth-century biological
revolution did not have to displace longstanding philosophical
and theological explanations.
Galileo
Darwin
Applied recently invented
apparatus (the telescope)
to answering scientific
questions.
Did not use specialized
apparatus. Gained insight
through meticulous
observation and analysis of
the natural world.
Our understanding of genetics came from a combination of these
two approaches. The Galilean approach is exemplified by the
application of newly invented physical and chemical methods
(radioactive tracers, X-ray crystallography) to answering biological
questions. The Darwinian approach is personified by Gregor
Mendel and his model of inheritance.
Gregor Mendel was an Austrian
monk trained in probability
mathematics and plant breeding.
He used pea plants as a model
experimental system. In these
experiments, he examined the
inheritance of characters like
flower color and seed shape by
mating plants and observing the
offspring.
Mendel followed heritable characters for three generations.
Mendel’s results refuted the blending
hypothesis. He proposed a particulate
theory of inheritance where characters
are determined by genes (recipes for a
character) that come in different
versions (alleles).
•Each parent has two alleles.
•Gametes contain only one allele.
•Offspring have two alleles - one
allele from each parent.
•When both alleles are present, the
dominant allele determines appearance.
•Gametes contain only one allele.
•Offspring have two alleles - one
allele from each parent.
•When both alleles are present, the
dominant allele determines appearance.
•This leads to a 3:1 ratio of offspring.
Most interesting characters
are influenced not by one or
two genes, but by dozens or
hundreds. In this example,
alleles at three loci control
skin color.
Environmental factors can
also influence these
polyfactorial characters.
The distribution shown here is
characteristic of polyfactorial
characters. These characters
vary continuously, rather than
in a few discrete states. Their
genetic component is still
inherited in a particulate
manner.
Although Darwin had access to Mendel’s work, he did not read it,
and it was left to later investigators to unify Mendelian genetics
with evolution.
The rediscovery and confirmation of Mendelian genetics in the
1930s strengthened the case for evolution and made mathematical
models of evolutionary change possible.
Evolution, in turn, provides the answers for genetic questions.
In addition to being genetically based, the modern synthesis of
genetics and evolution also allows for evolution by mechanisms
other than natural selection.
Theodosius Dobzhansky: "Nothing in biology makes sense
except in the light of evolution."
The combined power of
evolution and Mendelian
genetics to explain the
natural world stimulated
interest in the physical
nature of the gene.
Although most biologists
originally believed that
protein was the genetic was
the genetic material,
experimental evidence
pointed to DNA.
When Watson and Crick published the structure of DNA, many of
the functional characteristics became apparent.
The complementary nature of a DNA duplex allows each strand to
serve as the template for the synthesis of its partner.
DNA, by itself, is
biologically inert. It
is analogous to a
recipe, or to computer
software.
The proteins that are
the products of DNA
recipes carry out the
processes of life.
In general, all living
cells have the
hardware to make
protein from any
DNA recipe.
A deep understanding of the process of gene expression allows
biologists to make directed changes to organisms.
Examples:
•Bacteria that express human insulin
•Soybeans that are resistant to herbicides
•Cotton plants that manufacture their own pesticides
•Viral genes inserted into cancer cells to make them more
susceptible to chemotherapy
•Goats that secrete pharmaceuticals in their milk
In addition to making directed changes, biotechnology allows us to
find out about species, populations or individuals.
•How closely related are two species?
•How much genetic diversity is present in a given population?
•How are individuals related?
•Which individual donated this sample?
•To which diseases is this individual predisposed?
These techniques and questions represent the current state of
biology.
Future progress will center on understanding the function and
expression of gene families and networks, rather than isolated genes.
Genome —————> Proteome —————> Organism
Cookbook ———————————> What’s for Lunch?
In the early part of the 20th century, progress
in genetics was instrumental in supporting
and refining our understanding of evolution.
In the early part of the 21st century,
evolution guides the interpretation and
analysis of genomic data.
Comparing organisms at the
level of the genome allows us
to gain insight into the
function of conserved
sequences and to see
evolution in action in variable
regions.
Automated data collection
and analysis are necessary
to perceive patterns in
genomic and proteomic
data.
Recap
1. The science of genetics both informs and employs an
evolutionary perspective to understand the software of life. Recent
advances in genetics depend heavily on specialized apparatus, from
tunable X-ray sources to the most sophisticated robotics and
computers.
2. The revolution in molecular genetics is ongoing, moving from
analysis and manipulation of single genes and proteins to
understanding how networks of genes cooperate to produce
organisms.
3. Our current understanding of genetics and biochemistry allows
us to modify existing organisms in a directed way. Progress being
made now will allow much more sophisticated design of custom
organisms.
Non-biological questions:
1. Privacy - what if the results of a genetic test have important
implications for family members?
2. Third-party interests - should employers and insurers have access
to genetic information?
3. Intellectual property - who owns the information in the genome?
4. Human genetic manipulation - should directed or selective
manipulation of human genetics be encouraged, allowed, or
forbidden?