Unit 7 Biotech

Biotechnology

Manipulation of living organisms/organic material to serve human needs; using biology/DNA/organisms to make new products.

Examples of biotechnology

Yeast in food production (bread/alcohol); fungi antibiotics; cloning of plants; selective breeding; GMOs; genetic screening.

Biotechnology industries

Forensics; healthcare; agriculture.

Restriction enzymes (main idea)

Enzymes that act like molecular scissors to cut DNA to study or isolate specific genes.

Why biotech often starts by cutting DNA

Cutting targeted DNA pieces lets you isolate the gene/region you want to analyze or modify.

Restriction enzyme recognition site

A specific nucleotide sequence that a restriction enzyme recognizes and cuts.

Restriction enzymes (variety)

There are hundreds of restriction enzymes; each recognizes a different nucleotide sequence.

Blunt ends

DNA fragments formed when an enzyme cuts straight across both DNA strands.

Sticky ends

DNA fragments formed when an enzyme makes staggered cuts, leaving tails of unpaired bases on each fragment.

Why sticky ends are useful

Sticky ends can base-pair with complementary ends, making it easier to join DNA from different sources.

Ways to analyze DNA after cutting

Separate fragments and analyze them (often using gel electrophoresis).

Gel electrophoresis (definition)

A technique that uses an electric current to separate DNA fragments by size through a gel.

Gel electrophoresis setup

DNA is loaded into a gel with a negative electrode on one end and a positive electrode on the other.

Why DNA moves in gel electrophoresis

DNA has a negative charge, so fragments migrate toward the positive electrode.

Size vs speed in gel electrophoresis

Smaller DNA fragments move faster/farther through the gel than larger fragments.

Gel bands

Separated DNA fragments appear as bands; different sizes form bands at different positions.

Estimating DNA fragment length

Estimate fragment length by distance traveled: farther = smaller fragment.

PCR (purpose)

Amplify DNA so there is enough of a specific DNA sequence to study.

PCR (definition)

Polymerase Chain Reaction: produces millions of copies of a specific DNA sequence in a test tube in hours.

PCR ingredients (4)

Template DNA to be copied; DNA polymerase; lots of nucleotides (A/T/C/G); two primers.

PCR step 1: Denaturation

Heat to ~90°C to separate the two DNA strands.

PCR step 2: Annealing

Cool to ~55°C so primers bind to the DNA strands.

PCR step 3: Extension/Copying

Heat to ~72°C (polymerase works best) so nucleotides are added to build new strands.

PCR doubling rule

Each PCR cycle doubles the amount of target DNA.

PCR copy formula

Copies after n cycles = 2^n (starting from one original copy).

PCR example: 15 cycles

2^15 = 32,768 copies.

DNA fingerprinting (definition)

Identifies people at the molecular level using DNA fragment patterns.

DNA fingerprinting (what it can show)

Can show relationships among family members because related individuals have more similar patterns.

DNA fingerprinting (how it works)

DNA is cut with restriction enzymes, run through a gel, and band patterns are compared.

Why DNA fingerprints differ

People differ in DNA fragment sizes/number of repeats, creating different band patterns.

DNA fingerprinting uses: forensics

Match a suspect to DNA from a crime scene or exonerate suspects.

DNA fingerprinting uses: paternity

Find likelihood of a paternal relationship by comparing band patterns.

DNA fingerprinting uses: biodiversity

Study variation among organisms/populations by comparing DNA patterns.

Genetic engineering (definition)

Changing an organism’s DNA to give it new traits; genes can be inserted from one organism into another.

Recombinant DNA (definition)

DNA that combines genes from more than one organism.

Why bacteria are used in genetic engineering

Bacteria replicate quickly and contain plasmids that can be copied independently.

Plasmid (definition)

A tiny ring of DNA in bacteria that can be engineered to carry a desired gene.

Making recombinant DNA: step 1

Cut out the desired gene from DNA.

Making recombinant DNA: step 2

Cut open a plasmid.

Making recombinant DNA: step 3

Bond the gene’s complementary sticky ends to the plasmid using ligase.

DNA ligase (role)

Enzyme that “glues” DNA fragments together (seals the DNA backbone).

Making recombinant DNA: step 4

Resulting plasmid now contains recombinant DNA.

Transformation (definition)

Re-inserting the recombinant plasmid into a bacterium; the bacterium is now “transformed.”

What transformed bacteria do

They replicate, copying the recombinant plasmid (and the inserted gene) many times.

Humulin (what it is)

Human insulin that can be mass-produced by transgenic bacteria.

Humulin (historical note)

In 1982, Humulin was the first genetically modified drug produced and the first recombinant DNA drug approved by the FDA.

Genetic screening (definition)

Testing DNA to determine a person’s risk of having or passing on a genetic disorder.

Genetic screening (scope)

Tests exist for about 900 disorders.

Gene therapy (definition)

Replacement of a defective/missing gene or addition of a new gene into a person’s genome to treat disease.

Gene therapy (big idea)

Uses DNA changes as treatment; has major potential.

Cloning (natural vs artificial)

Can be natural or artificial; many organisms can clone themselves, but mammals cannot naturally.

Mammal cloning overview (nuclear transfer)

Nucleus from the animal to be cloned is implanted into an egg with its nucleus removed, then embryo is placed in a surrogate.

Mammal cloning step 1

Remove the nucleus from an unfertilized egg.

Mammal cloning step 2

Implant nucleus from a body cell of the animal to be cloned into the egg.

Mammal cloning step 3

After embryo grows for a few days, transplant it into a surrogate mother.

Bioethics (definition)

Ethical concerns about whether/how humans should “mess with nature” using biotechnology.

GMO (definition)

Genetically Modified Organism; often used in agriculture (crops).

GMO pros (examples)

Contain fewer pesticides; grow more efficiently; can be engineered to have more nutrients.

GMO cons (examples)

Cost more to grow (hard for small farms to compete); decrease genetic diversity (more vulnerable to pests/disease).

Bioethics example: increased production

Animals genetically modified to produce much more milk (production benefit; animal welfare concern).

Bioethics example: new materials

Organisms genetically modified to produce spider silk (useful material; ethical questions).

Bioethics example: conservation/stem cells

Using stem cells to make a “mini brain” of the last rhino (scientific potential + ethical concerns).