How was Ruffin’s innocence
GUILTY or INNOCENT?
Traditional Applications of Biotechnology
date back to over 10,000 years ago
Use of yeast to produce beer and wine in Egypt and Near
Selective breeding of plants
Selective breeding of animals
Any use or alteration of organisms, cells, or biological
molecules to achieve specific practical goals
13.1 What Is Biotechnology?
the modification of genetic material to achieve specific goals
major goals including
learning more about cellular processes:
inheritance and gene expression
providing better understanding and treatment of disease
generating economic and social benefits
A key tool:
recombinant DNA technology
genetically modified organisms (GMOs)
associated techniques for
analyzing biological molecules
especially DNA and protein
is an important tool biotechnology
Due to crossing over during meiosis, each
chromosome in a gamete contains a mixture of alleles
from the two parental chromosomes
Thus, eggs and sperm contain recombinant DNA
13.2 How Does DNA Recombine in
May Combine DNA
from Different Bacterial Species
around 4,600 kbp)
DNA fragment is
A single bacterium may contain dozens or
even hundreds of copies of a plasmid
What use are plasmids?
Genes carried by plasmids allowing
the bacteria carry them to
grow in novel environments
metabolize unusual energy sources
cause disease symptoms
, such as diarrhea, in the animal
or other organism that the bacterium infects
enable bacteria to
grow in the presence of antibiotics
Viruses May Transfer DNA
Viral life cycle
Viral particle invades host cell
Viral DNA is replicated
Viral protein molecules are synthesized
Offspring viruses are assembled and break out of the
Viral transfer of DNA
Viruses may package some genes from host cell into viral
particles during assembly
Infection of new host cell injects genes from previous host,
allowing for recombination
Virus releases its DNA into
host cell; some viral DNA (red)
host cell’s DNA (blue).
Host cell bursts, releasing newly
assembled viruses. When “hybrid
a second cell, they may
transfer genes from the first cell to
the second cell
New viruses assemble; host
cell DNA is carried by “
Virus enters host cell.
host cell DNA
Virus attaches to
susceptible host cell.
Viral genes encode synthesis
of viral proteins and viral gene
replication. Some host cell DNA
may attach to replicated viral
Biotechnology and Forensics
is the science of criminal and victim identification
DNA technology has allowed forensic science to identify victims
and criminals from trace biological samples
Genetic sequences of any human individual are unique
DNA analysis reveals patterns that identify people with a high
degree of accuracy
13.3 How Is Biotechnology Used in
Developed by Kary B. Mullis of the Cetus Corporation in 1986
Acquired the Nobel Prize for Chemistry in 1993.
Forensic technicians typically have very little DNA with which to
Polymerase Chain Reaction
) produces virtually unlimited
copies of a very small DNA sample
PCR requires small pieces of DNA (called
) that are
complementary to the
A PCR “run” is basically DNA replication in a tiny test tube
are all in the reaction mix
PCR copies a specific DNA sequence
One PCR cycle
base pairs with DNA
of the DNA segment
primers and DNA
polymerase to bind.
Repetition of the cycle
(b) Each PCR cycle doubles the number of copies of the DNA
to be amplified
about 1 million copies
about 1 billion copies
Choice of Primers
Segments of DNA Are Amplified
How would a forensics lab know which primers to use?
Small, repeating segments of DNA called
short tandem repeats
) can be used to identify people with astonishing accuracy.
5 nucleotides long and usually in introns.
side (tandem) repeats
of the same 4
This STR, called D5, is not part of any known gene. The sequence AGAT
may be repeated from7 to 13 times in different individuals.
Why is the copy number of an individual STR so much
STRs probably have no biological function.
As a result, DNA replication errors that lead to different numbers
of STR repeats are not selected against during evolution, and
variability has accumulated over evolutionary time.
In 1999, British and American law enforcement agencies agreed to
use a set of 10 to13 STRs each 4 nucleotides long, that vary greatly
that amplify only the DNA immediately
surrounding the STRs.
How does the lab determine how many repeats occurred in
their DNA samples?
Identifies DNA Segments
Most of sophisticated & expensive machines are based on two methods:
Separating the DNA segments with different sizes by
DNA samples are pipetted into wells (shallow slots) in the gel.
Electrical current is sent through the gel (negative at end with
wells, positive at opposite end.)
2. Labeling specific DNA fragments of interest
not yet visible
Electrical current moves DNA segments through the
gel. Smaller pieces of DNA move farther toward the
Gel is placed on special nylon “paper.” Electrical
current drives DNA out of gel onto nylon.
The phosphate groups in the backbones of DNA
the negatively charged DNA fragments
) electrode to (+) electrode
Are Used to Label
Specific Nucleotide Sequences
STR #1: probe base
pairs and binds
STR #2: probe cannot base
pair; does not bind
identify the location of
a gene sequence by
the band containing it
How can a technician
How does nature
solution of DNA
Nylon paper with DNA is bathed in a solution of
labeled DNA probes (red) that are complementary to
specific DNA segments in the original DNA sample.
Complementary DNA segments are labeled by
probes (red bands).
In modern forensic
analysis, the STRs are
usually directly labeled
with colored molecules
during the PCR and
labeled DNA probes
are not required
In modern STR analysis, the suspect and crime scene DNA
samples can be run on different gels, in different states or
The numbers and positions of the bands on the gel can be
determined by the numbers of repeats of each STR.
The numbers of bands for a sample:
Appeared 2 bands for one person
The STR gene is
How’s about a homozygous STR gene?
The position of a band shows the copy number of the DNA
13.3.4 Every Person Has a Unique
DNA samples run on STR gels produce a pattern, called
a DNA profile
D16: an STR on chromosome 16
DNA samples from
13 different people
Number of repeats
For the first person
PentaD, D7 and D13: 2 bands
CSF, D16 and D5: one band
For the D16 STR
The first person’s DNA:
12 repeats and homozygous
The second person’s DNA:
12 & 13 repeats and heterozygous
Copyright © 2005 Pearson Prentice Hall, Inc.
13.4 How Is Biotechnology Used in
13.4.1 Many Crops Are Genetically Modified
Commonly modified to improve the crops’ resistance to insects & herbicides
Crop plants are commonly modified to improve insect
and herbicide resistance
Herbicide resistant crops withstand applications of
can be inserted into plants to produce insect
protein in crops
The Desired Gene Is
Cloning a gene usually involved two tasks: (1) obtaining the gene &
(2) inserting it into a plasmid
huge numbers of gene copy
Obtaining a gene via two ways:
(1) Isolating the gene from the organism that makes it
(2) Synthesizing the gene using PCR or DNA synthesizers
Producing huge numbers of copies of the gene by inserting the
target gene into a plasmid and plasmid manipulation in bacterial
Why insert the desired gene into a plasmid?
producing huge numbers of copies of the gene simply
the gene separated from the bacteria fairly easily
plasmids may then be taken up by other bacteria or …
Restriction Enzymes Cut DNA at Specific
(EcoRI) binds to
the GAATTC sequence and cuts the DNA,
creating DNA fragments with “sticky ends.”
Cutting Two Pieces of DNA with the Same Restriction
Enzyme Allows the Pieces to Be Joined Together
Cut both with the same restriction enzyme.
gene and plasmid; add
DNA ligase to seal DNA.
By manipulating the plasmids and bacteria appropriately,
biotechnologists can isolate and grow only the bacteria with the
T i p l a s m i d
t u m o r
i n d u c i n g p l a s m i d
的 縮 寫 ， 這 是 一 種
土 壤 瘤 痂 桿 菌 中 特 有 的 細 菌 性 質 體 ， 其 上 有 特 殊 的 致 病 基 因 ，
可 藉 由 細 菌 感 染 而 進 入 植 物 細 胞 ， 造 成 植 物 的 腫 瘤 生 成 。
投 影 片
Plasmids Are Used to Insert the Bt Gene Into a Plant
Infect plant cell with transgenic bacterium.
which can infect many
gene into plant chromosome.
Every time that plant cell divides, it replicates the Ti plasmid
all of its daughter cells inherit the Ti DNA and
carry the Bt gene
Appropriate hormonal treatments
stimulate the transgenic plant
cells to divide and differentiate into entire plants.
13.4.2 Genetically Modified Plants May Be Used
to Produce Medicines
A plant could be engineered to produce harmless proteins that
are normally found in disease
causing bacteria or viruses.
against diseases, such that p
otatoes have been
engineered to produce harmless hepatitis B virus and
proteins, stimulating an immune response when eaten
Plants could be engineered to produce
conferring passive immunity to microbial infection merely by
eating the plant
13.4.3 Genetically Modified Animals May Be Useful
in Agriculture and Medicine
) animals can be engineered
by incorporating genes into chromosomes of a fertilized egg
Healthy transgenic animals are difficult to engineer
Growth hormone genes have been inserted into
pigs and fish species but some abnormalities
have been observed
Animals like sheep might be engineered to produce
medically important proteins in their milk
Resistance against pathogens
13.5 Biotechnology and the Human
Human genome contains ~25,000 genes
New genes, including many disease
genes have been discovered
Has determined the nucleotide sequence of all
the DNA in our entire set of genes, called the
The genes comprise 2% of all the DNA
Many genes were discovered whose functions
are completely unknown.
Allows biologists to predict the AA sequences of
the proteins…comparing those well known
Improved diagnosis, treatment and cures of
genetic disorders or predispositions
Comparison of our genome to those of other
species will clarify the genetic differences that
help to make us human
Help us to appreciate our place in the evolution
of life on Earth
13.6 How Is Biotechnology Used for
Medical Diagnosis and Treatment?
13.6.1 DNA Technology Can Be Used to
Diagnose Inherited Disorders
Defective alleles differ from normal,
functional alleles because of differences in
A particular restriction enzyme may cut two different
alleles of a gene differently
Differences in nucleotide sequence within genes
produces different numbers of cutting sites and
different lengths of fragments
Differences in restriction enzyme fragments between
genes are known as
restriction fragment length
RFLP differences are revealed in gel electrophoresis
May Cut Different Alleles of a
Gene at Different Locations
Why is this used?
If different people have different RFLPs, this can be
used to identify DNA samples
With diligent research and a little luck, m
important alleles can sometimes be identified by
differences in the lengths of the restriction fragments
produced by cutting with a specific RE.
Mst II cuts a normal globin allele in 2 places, but cuts the
cell allele in 1 place.
cell anemia with REs
Gel electrophoresis of globin alleles
AA = homozygous normal
AS = heterozygote
SS = homozygous sickle
Defective alleles can also be identified using DNA probes
DNA probing is especially useful where there are many different
alleles at a single gene locus
Cystic fibrosis is a disease caused by any of 32 alleles out of
1000 total possible alleles
Different Alleles May Bind to Different
Arrays of single
stranded DNA complementary to each of the
defective alleles can be bound to filter paper
complementary DNA for normal allele
A person’s DNA is cut into small pieces, separated into single
strands & labeled.
The array is then bathed in the resulting
solution of labeled DNA fragments (blue).
Strands of DNA binding to complementary sequence on the paper
indicate presence of a defective allele in person’s genome
A cystic fibrosis diagnostic array
An expanded version of this
type of DNA analysis is
known as a
A microarray contains up to
thousands of probes for a
variety of disease
Microarray analysis has the
potential to comprehensively
identify disease susceptibility.
13.6.2 DNA Technology Can Be Used to Treat
All products are proteins which do not cure inherited disorders
184.108.40.206 Using Biotechnology to Treat Cystic Fibrosis
220.127.116.11 Using Biotechnology to Cure Severe
Combined Immune Deficiency
13.7 What Are the Major Ethical Issues of
18.104.22.168 Are Foods from GMOs Dangerous to Eat?
22.214.171.124 Are GMOs Hazardous to the Environment?
13.7.1 Should Genetically Modified Organisms Be
Permitted in Agriculture?
GM Organisms in Agriculture
The goal of breeding or genetically modifying plants or
livestock is to make them more productive, efficient, or useful
Genetic modification differs from selective breeding
Genetic engineering is much more rapid
Genetic engineering can transfer genes between species
Genetic engineering can produce new genes never seen
before on Earth
Benefits of genetically modified plants
Transgenic crops decrease applications of pesticides,
saving fuel, labor, and money
GM plants can be sold at a lower price due to farm savings
Genetically engineered crops can deliver greater amounts of
vitamins (e.g. “golden rice” which produces vitamin A)
Scientific Objections to GMOs
Safety issues from eating GMOs
Could ingestion of Bt protein in insect
resistant plants be
dangerous to humans?
Are transgenic fish producing extra growth hormone
dangerous to eat?
Could GM crops cause allergic reactions?
USDA now monitors GM foods for allergic potential
Toxicology study of GM plants (2003) concluded that
ingestion of current transgenic crops pose no significant
Environmental hazards posed by GMOs
Pollen from modified plants can carry GM genes to the wild
Could herbicide resistance genes be transferred to
weed species, creating
Could GM fish reduce biodiversity in the wild population if
Reduced diversity in wild fish makes them more
susceptible to catastrophic disease outbreaks
US found to lack adequate system to monitor changes in
ecosystem wrought by GMOs (National Academy of
Science Study 2003)
Should parents be given information about the genetic health
of an unborn fetus?
Should parents be allowed to select the genomes of their
fertilization are currently tested
Many unused embryos are discarded
Should parents be allowed to design or correct the genomes
of their offspring?
13.7.2 Should the Genome of Humans Be Changed
Bone marrow failure…….
Allowing physicians only to select among existing embryos,
not to change their genomes.
cell culture: biochemical
analysis, analysis using
Prenatal Genetic Screening