Chapter 13 Biotechnology 13.1 What is biotechnology? 13.2 How does DNA recombine occur in nature? 13.3 How is biotechnology used in forensics science?

Chapter 13Biotechnology

• 13.1 What is biotechnology?

• 13.2 How does DNA recombine occur in nature?

• 13.3 How is biotechnology used in forensics science?

• 13.4 How is biotechnology used in agriculture?

Chapter 13Biotechnology

• 13.5 How is biotechnology used to learn about the human genome?

• 13.6 How is biotechnology used for medical diagnosis and treatment?

• 13.7 What are the major ethical issues surround modern biotechnology?

13.1 What Is Biotechnology?

Any industrial or commercial use or alternation of organisms, cells or biological molecules to achieve specific practical goals

Genetic engineering – modification of genetic material

GMOs (transgenic) – genetically modified organisms

Sexual Reproduction

• 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

Transformation

• Bacteria can naturally take up DNA from the environment (transformation) and integrate the new genes into the genome (recombination)

– Transformation with DNA fragment– Transformation with plasmid

Transformation

• Small circular DNA molecules (plasmids) carry supplementary genes

– Plasmid genes may allow bacteria to grow in novel environments

– Plasmid genes may enhance virulence of bacteria in establishing an infection

– Plasmid genes may confer resistance to antimicrobial drugs

Viral Transfer of DNA

• Viral life cycle1. Viral particle invades host cell

2. Viral DNA is replicated

3. Viral protein molecules are synthesized

4. Offspring viruses are assembled and break out of the host cell

Viral Transfer of DNA

• 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

• Viruses may transfer DNA between bacteria and between Eukaryotic species

Biotechnology and Forensics

• 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 Forensics?

• The Polymerase Chain Reaction Amplifies DNA– PCR copies a specific DNA sequence– Need high temperatures to separate DNA

strands– But then a special DNA polymerase that

wouldn’t fall apart at high temperatures is needed

Polymerase Chain Reaction

• Four steps of a PCR cycle1. Template strand separation

– The test tube is heated to 90-95oC to cause the double stranded template DNA to separate into single strands…


• Four steps of a PCR cycle2. Binding of the primers

– The temperature is lowered to 50oC to allow the primer DNA segments to bind to the targeted gene sequences through hydrogen bonding…


• Four steps of a PCR cycle3. New DNA synthesis at targeted sequences

– The temperature is raised to 70-72oC where the heat-stable DNA polymerase synthesizes new DNA of the sequences targeted by the primers…


• Four steps of a PCR cycle4. Repetition of the cycle

– The cycle is repeated automatically (by a thermocycler machine) for 20-30 cycles, producing up to 1 billion copies of the original targeted DNA sequence

Thomas Brock surveys Mushroom Spring. Thermus aquaticus


• Choice of primers determines which sequences are amplified (copied)

• Forensic scientists focus on short tandem repeats (STRs) found within the human genome


• STRs are repeated sequences of DNA within the chromosomes that do not code for proteins

• STRs vary greatly between different human individuals

• A match of 10 different STRs between suspect and crime scene DNA virtually proves the suspect was at the crime scene

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This STR, called D5, is not part of any known gene.

13.3 How Is Biotechnology Used in Forensics?

• Gel Electrophoresis Separates and Identifies DNA Segments– Gel electrophoresis is used to separate and

identify segments of DNA– DNA fingerprinting– DNA probe

DNA Probes

• DNA probes are short single-stranded DNA fragments used to identify DNA in a gel pattern

– Probe sequence is complementary to a DNA fragment somewhere in the gel pattern

STR #1: probe base-pairs and binds

STR #2: probe cannot base-pair; does not bind

probe label(colored molecule)

DNA Probes

• DNA probes– Probes may have colored molecules attached

to them to allow for visual identification of the bands to which they bind

– Gel DNA pattern is usually transferred to piece of nylon paper before probing

DNA Fingerprinting

• DNA from a crime scene sample can be amplified by PCR and run on a gel with suspect DNAs

• Short tandem repeats (STRs) in the gel DNA can be identified by DNA probes

DNA Fingerprinting

• Distinctive pattern of STR numbers and lengths are fairly unique to a specific individual (forming a DNA fingerprint)

• DNA fingerprint from crime scene can be matched with DNA fingerprint of suspect

13.4 How Is Biotechnology Used in Agriculture?

• Many Crops Are Genetically Modified– Genetically Engineered Crops with USDA

Approval– In 2002, 34% of corn, 71% of cotton & 75% of

soybeans were GMOs– In 2005, 52% of corn, 79% of cotton & 87% of

soybeans were GMOs– Not required to be labeled in US

Many Crops Are Genetically Modified

• Crop plants are commonly modified to improve insect and herbicide resistance

– Herbicide resistant crops withstand applications of weed-killing chemicals

– Bt gene (from Bacillus thuringiensis bacterium) can be inserted into plants to produce insect-killing protein in crops

Cloning of the Desired Gene

• Modifying a plant genetically begins with gene cloning

1. Desired gene is first isolated from organism containing it• Desired gene may alternately be synthesized in the

laboratory

Cloning of the Desired Gene

• Modifying a plant genetically begins with gene cloning

2. Gene is next inserted into a small DNA circle called a plasmid which replicates itself autonomously in bacterial cells

Restriction Enzymes Cut DNA

• A DNA sequence (e.g. a gene) can be removed from a chromosome using special enzymes

• Restriction enzymes are nucleases that cut DNA at specific nucleotide sequences


– The desired gene is cloned– Restriction enzymes cut DNA at specific

nucleotide sequences– Cutting two pieces of DNA with the same

restriction enzyme allows the pieces to be joined together

• Using Agrobacterium tumefaciens to insert the Bt gene into plants

Transgenic salmon (bottom) grow much faster than their wild relatives (top)


• Genetically modified plants may be used to produce medicines

• Genetically modified animals may be useful in agriculture and medicine

13.5/13.6 How Is Biotechnology Used for Medical Diagnosis and

Treatment?

• DNA technology can be used to diagnose inherited disorders– Restriction enzymes may cut different

alleles of a homologous pair of chromosomes at different locations

– RFLPs: Restriction length polymorphisms “riff-lips”

DNA Probes

• 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

DNA Probes

• Arrays of single-stranded DNA complementary to each of the defective alleles can be bound to filter paper

1. A person’s DNA sample is cut up and separated into single-strands

2. The array is bathed in the DNA sample

3. Strands of DNA binding to complementary sequence on the paper indicate presence of a defective allele in person’s genome

DNA Probes

• An expanded version of this type of DNA analysis is known as a microarray

• A microarray contains up to thousands of probes for a variety of disease-related alleles

• Microarray analysis has the potential to comprehensively identify disease susceptibility

Disease Treatment

• Treatments using DNA technology– Administration of proteins to treat but not cure

a disorder

• Human insulin produced inexpensively and rapidly in recombinant bacteria for diabetics

• Growth hormone and blood clotting factors produced safely and inexpensively in recombinant bacteria

Disease Treatment

• Treatments using DNA technology– Replacing defective genes to possibly cure a

disorder

• Replacement of defective cystic fibrosis allele using a virus to carry in a functional gene sequence into patient lung cells

• Defective bone marrow cell DNA replacement by functional gene in severe combined immune deficiency (SCID) patients

Section 13.7 Outline• 13.7 Biotechnology and Ethics

– Issues Surrounding GM Organisms in Agriculture

– Scientific Objections to Genetically Modified Organisms

– Ethics of Using Biotechnology on the Human Genome

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 (“traditional biotechnology”)

– 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?


• Safety issues from eating GMOs– 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 health dangers


• Environmental hazards posed by GMOs– Pollen from modified plants can carry GM

genes to the wild plant population• Could herbicide resistance genes be transferred to

weed species, creating superweeds?


• Environmental hazards posed by GMOs– Could GM fish reduce biodiversity in the wild

population if they escape?• Reduced diversity in wild fish makes them more

susceptible to catastrophic disease outbreaks


• Environmental hazards posed by GMOs– US found to lack adequate system to monitor

changes in ecosystem wrought by GMOs (National Academy of Science Study 2003)

The Human Genome

• Should parents be given information about the genetic health of an unborn fetus?

• Should parents be allowed to select the genomes of their offspring?

– Embryos from in vitro fertilization are currently tested before implantation

– Many unused embryos are discarded

• Should parents be allowed to design or correct the genomes of their offspring?

Documents

Chapter 13 Biotechnology 13.1 What is biotechnology? 13.2 How does DNA recombine occur in nature? 13.3 How is biotechnology used in forensics science?