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Biotechnology:
How Do We Use What We Know
about Life?
Role of bacteria in technology
• Advantage to using bacteria
– Possess plasmids
• Small extra loops of DNA
– Experience transformation
• Bacteria take up plasmids from surroundings
Role of bacteria in technology
• Advantage to using
bacteria:
– Scientists can
genetically engineer
plasmids by inserting
gene of interest into
bacterial plasmid.
Gene Cloning
• Definition: using bacteria to make multiple
identical copies of a single stretch of DNA.
• Useful in understanding eukaryotic genome.
• Cloning Vector:
– Any vehicle that inserts a fragment of foreign
DNA into the genome of a host cell.
– Example: virus or genetically engineered
plasmid.
– Used in gene therapy.
Genetic Engineering
• Definition: Ability to
precisely manipulate DNA
sequences from widely
different organisms.
• Process requires
– Ability to cut DNA
– To insert foreign DNA
segment
– “Glue” DNA sequences
together
Molecular Scissors
• Restriction enzymes:
– Cut DNA at specific places called recognition sites.
– Form “sticky ends.”
Restriction Sites
Molecular Paste
• DNA Ligase:
– Form bonds between the sugar and phosphate
backbone of the DNA molecule.
• Restriction enzymes and DNA ligase make
possible the combination of DNA from
different organisms into one DNA molecule
– Called recombinant DNA
Making Recombinant DNA
How do we know what size DNA
fragments we have?
• Agarose gel
electrophoresis:
– Allows separation of
DNA on the basis of
size.
– Can visualize DNA to
determine exactly how
large it is.
Making a DNA library
• Need the following:
–
–
–
–
A gene of interest
Restriction enzymes
Plasmids
DNA ligase
• Can create a cloning vector using these
tools which can be inserted in a bacteria
• Allow bacteria to reproduce
• DNA library: entire collection of bacterial
cells which contain cloned gene
Screening a DNA Library
• Need to find the gene of interest in the
bacteria or bacterial cells that possess the
gene of interest.
• Use nucleic acid hybridization to find the
gene of interest.
Nucleic Acid Hybridization
• Requires a molecular probe:
– Probe is made of a synthetic single-stranded
DNA whose sequence is complementary to the
gene of interest.
– Also has a built-in marker so scientists can find
it.
• When probe binds to denatured gene of
interest, a hybrid is formed.
Polymerase Chain Reaction
• Allows scientists to make copies of a small
sample of DNA.
• Requires:
– Primers: two synthetic short strands of DNA
that are complementary to each of the two DNA
sequences that flank the gene or DNA to be
copied.
– Heat-resistant DNA polymerase
– Nucleotides
DNA Sequencing
• Determining the baseby-base order of the
nucleotides in a stretch
of DNA.
• Can help us identify
regions of DNA that
contain genes.
DNA Sequencing
• Makes possible comparisons of DNA
sequences
– between individuals to teach us about our
susceptibility to disease.
– between species to teach us about how we
evolved.
• Also, DNA sequences teach us about the
regulation of gene expression.
Human Genome Project (HGP)
• Overall goal:
– decipher the full set
of genetic
instructions in
human DNA.
– Develop a set of
instructions as a
research tool for
scientists.
Human Genome Project (HGP)
• Several genomes of
model organisms
have been
sequenced as a part
of the project.
What We Have Learned From
Human Genome
• First lesson:Human DNA consists of 3
billion base pairs
– Contain 20,000-25,000 genes
• 2-3 times as many genes as a worm or fruit
fly.
• Approximately 3% of DNA contains the
information to make proteins.
What We Have Learned From
Human Genome
• Second lesson: a greater understanding of
genes themselves.
– Has important implications to understanding
human biology and what goes wrong in disease
states.
– Help us define disease states and predict
possible candidates who are likely to suffer
from a disease based on their nucleotide
sequences.
What We Have Learned From
Human Genome
• Third lesson: lessons about the human
family; both our diversity and evolution.
– Compare base-by-base sequences of DNA
• Any group of individuals have DNA sequences that
are 99.9% identical regardless or origin or ethnicity.
• Points in DNA sequence where the sequences are
not identical between two or more individuals are
called single nucleotide polymorphisms (SNPs)
HPG has Raised Ethical, Social
and Legal Issues
• Who owns genetic
information?
• Should people be
tested for genetic
disorders if there is no
possibility of
treatment?
How Do We Use Biotechnology?
• Gene therapy:
treatment of a genetic
disease by alteration of
the affected person’s
genotype, or the
genotype of the
affected cells.
Stem Cells
• Definition: undifferentiated cells in either
an adult or embryo that can undergo
unlimited number of cell divisions.
– Are totipotent
• Could be used to produce complex human
tissues or replacement organs for people
suffering from disease.
Designer Drugs
• Biotechnology has made it possible to predict the
precise shape of molecules.
– Makes it possible to develop drugs for
therapeutic use.
DNA in The Courtroom
• Can be use to determine paternity
• Identifying individuals in criminal and civil
proceedings.
• Use variable number tandem repeats (VNTR) as
markers.
DNA in The Courtroom
Biotechnology on The Farm
• Goal: To increase the
world’s food
production while
decreasing the costs
and environmental
damage due to
insecticide and
pesticide use.
Biotechnology on The Farm
• Scientists have focused efforts on three areas:
– Developing crops capable of fending off insect
pests without the use of insecticides
– Engineering plants with a greater yield that grow
in a wider ranges of climates
– Make crops that are resistant to herbicides , so that
fields can be treated for weeds without damaging
crops
• Opponents wondering if we are disturbing
ecological balance in the environment
Can Biotechnology Save The
Environment?
• Bioremediation: Use
of microorganisms to
decompose toxic
pollutants into less
harmful compounds.
Risks of Biotechnology
• Two categories of
risks:
– Risks to human
health
– Risks to the
environment
Questioning The Ethics of
Biotechnology
• Privacy and ownership of genetic
information.
• Argue altering genes is unnatural.
– Breaches fundamental boundaries between
species.
• Are scientists interfering with the order of
life?
Where Are We Now?