Code of Life Topic 5Genetic analyses &

Genetic engineering

(An incomplete) timeline of genetics

1944 Avery

1952

1958

1968

1953 1972

1973

1975-77

1983

1990

Applications• Genetic analyses and engineering

Isolating genes• Use special proteins to cut

the DNA strand at specific places

• Restriction enzymes:– Target very specific base

sequences– Are found in more than 100

different varieties– Are used in nature to protect

bacteria from foreign invaders

Restriction Enzymes

• Each restriction enzyme recognizes a very specific nucleotide sequence

Example: EcoR1 recognizesGAATTC CTTAAG

The enzyme cuts it:G AATTC

CTTAA G

Which DNA segments are used?

• Short tandem repeats (STRs)

• Good for “fingerprinting”

Which DNA segments are used?

• Single nucleotide polymorphisms (SNPs) • Catalog of human SNPs

• Restriction fragment length polymorphisms (RFLPs) are SNPs that change the length of restriction fragments

Restriction Fragment Length Polymorphisms (RFLPs)

Analyzing the differences between people

STEPS

1.Use restriction enzymes to cut the DNA

2.Load the DNA onto agarose gel for gel electrophoresis

3.Analyze the banding pattern

Gel Electrophoresis• Separates DNA fragments by size using

electric current

Gel Electrophoresis• Larger fragments move more slowly

• Results in bands of DNA fragments of different lengths

DNA Analysis• Useful for:

– Forensic science (crime scene “fingerprints”)– Determining paternity – Looking at disease risk

Lab!

• We will be conducting a lab to determine whether or not a young woman carries one or two copies of a mutant gene

• The mutated version of the gene is responsible for Tay Sach’s disease.

• How do you think we will go about this?– RFLPs and gel electrophoresis

• Besides the young woman’s, whose DNA should we also look at?

To test or not to test?

• PGD

• During pregnancy

• After birth/during childhood

• As an adult

• Bioethics

Genetic engineering

Changing the DNA of organisms

Recombinant DNA• DNA that is combined from two different

organisms.• Common/first example: insertion of a gene from

an animal into bacteria to harvest protein Important players:– Gene of interest (i.e. insulin, hGH, etc)– Restriction enzymes– Plasmid– Host bacteria

Making Recombinant DNA

• Plasmids - self-replicating rings of DNA containing 2-30 genes, found in bacterial cells

• Plasmid and gene of interest cut with same restriction enzymes

• Plasmid and gene have complementary “sticky” ends

Making Recombinant DNA

1. Cut the gene of interest using a restriction enzyme

2. Cut the plasmid (using the same enzyme)

3. Insert gene into the plasmid

4. Insert the plasmid into bacteria

5. Grow bacteria and harvest the protein

How could you tell if the transformation really took place?

Genetic Engineering Applications

• Pest-resistant crops (Bt toxin)

Genetic Engineering Applications

• Herbicide-resistant crops • Fast-growing fish• Green-glowing

aquarium fish (jellyfish genes)

• Bacterial drug production (insulin, hGH)

Diagram on p. 14 in your packet (for #1-4)

Diagram on p. 15 in your packet (for #6-7)