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Biotechnology
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A Brave New World
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human genome 3.2 billion bases
TACGCACATTTACGTACGCGGATGCCGCGACTATGATCACATAGACATGCTGTCAGCTCTAGTAGACTAGCTGACTCGACTAGCATGATCGATCAGCTACATGCTAGCACACYCGTACATCGATCCTGACATCGACCTGCTCGTACATGCTACTAGCTACTGACTCATGATCCAGATCACTGAAACCCTAGATCGGGTACCTATTACAGTACGATCATCCGATCAGATCATGCTAGTACATCGATCGATACTGCTACTGATCTAGCTCAATCAAACTCTTTTTGCATCATGATACTAGACTAGCTGACTGATCATGACTCTGATCCCGTAGATCGGGTACCTATTACAGTACGATCATCCGATCAGATCATGCTAGTACATCGATCGATACTGCTACTGATCTAGCTCAATCAAACTCTTTTTGCATCATGATACTAGACTAGCTGACTGATCATGACTCTGATCCCGTAGATCGGGTACCTATTACAGTACGATCATCCGATCAGATCATGCTAGTACATCGATCGATACT human genome 3.2 billion bases
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Biotechnology today Genetic Engineering Our tool kit…
manipulation of DNA if you are going to engineer DNA & genes & organisms, then you need a set of tools to work with this unit is a survey of those tools… Our tool kit…
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Bacteria Bacteria review one-celled prokaryotes reproduce by mitosis
binary fission rapid growth generation every ~20 minutes 108 (100 million) colony overnight! dominant form of life on Earth incredibly diverse
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How have these little guys gotten to be so diverse??
Bacterial genome Single circular chromosome haploid naked DNA no histone proteins ~4 million base pairs ~4300 genes 1/1000 DNA in eukaryote Genome = all the DNA of an organism Eukaryotes • 1000 times more DNA • only 10 times more genes - introns, spacers, inefficiency How have these little guys gotten to be so diverse??
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Transformation Bacteria are opportunists
promiscuous!? Bacteria are opportunists pick up naked foreign DNA wherever it may be hanging out have surface transport proteins that are specialized for the uptake of naked DNA import bits of chromosomes from other bacteria incorporate the DNA bits into their own chromosome express new genes transformation form of recombination mix heat-killed pathogenic & non-pathogenic bacteria While E. coli lacks this specialized mechanism, it can be induced to take up small pieces of DNA if cultured in a medium with a relatively high concentration of calcium ions. In biotechnology, this technique has been used to introduce foreign DNA into E. coli. mice die
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Plasmids Small supplemental circles of DNA carry extra genes
,000 base pairs self-replicating carry extra genes 2-30 genes genes for antibiotic resistance can be exchanged between bacteria bacterial sex!! rapid evolution can be imported from environment Mini-chromosomes
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How can plasmids help us?
A way to get genes into bacteria easily insert new gene into plasmid insert plasmid into bacteria = vector bacteria now expresses new gene bacteria make new protein transformed bacteria gene from other organism recombinant plasmid vector plasmid cut DNA + glue DNA
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insert “gene we want” into plasmid... “glue” together
Biotechnology Plasmids used to insert new genes into bacteria cut DNA gene we want like what? …insulin …HGH …lactase cut plasmid DNA Cut DNA? DNA scissors? ligase insert “gene we want” into plasmid... “glue” together recombinant plasmid
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How do we cut DNA? Restriction enzymes restriction endonucleases
discovered in 1960s evolved in bacteria to cut up foreign DNA “restrict” the action of the attacking organism protection against viruses & other bacteria bacteria protect their own DNA by methylation & by not using the base sequences recognized by the enzymes in their own DNA
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What do you notice about these phrases?
radar racecar Madam I’m Adam Able was I ere I saw Elba a man, a plan, a canal, Panama Was it a bar or a bat I saw? go hang a salami I’m a lasagna hog palindromes
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Restriction enzymes Madam I’m Adam Action of enzyme
cut DNA at specific sequences restriction site symmetrical “palindrome” produces protruding ends sticky ends will bind to any complementary DNA Many different enzymes named after organism they are found in EcoRI, HindIII, BamHI, SmaI CTGAATTCCG GACTTAAGGC CTG|AATTCCG GACTTAA|GGC
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Discovery of restriction enzymes
Werner Arber Daniel Nathans Hamilton O. Smith Restriction enzymes are named for the organism they come from: EcoRI = 1st restriction enzyme found in E. coli Werner Arber discovered restriction enzymes. He postulated that these enzymes bind to DNA at specific sites containing recurring structural elements made up of specific basepair sequences. Hamilton Smith verified Arber's hypothesis with a purified bacterial restriction enzyme and showed that this enzyme cuts DNA in the middle of a specific symmetrical sequence. Other restriction enzymes have similar properties, but different enzymes recognize different sequences. Ham Smith now works at Celera Genomics, the company who sequenced the human genome. Dan Nathans pioneered the application of restriction enzymes to genetics. He demonstrated their use for the construction of genetic maps and developed and applied new methodology involving restriction enzymes to solve various problems in genetics.
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restriction enzyme cut site restriction enzyme cut site
Restriction enzymes Cut DNA at specific sites leave “sticky ends” restriction enzyme cut site GTAACGAATTCACGCTT CATTGCTTAAGTGCGAA restriction enzyme cut site GTAACG AATTCACGCTT CATTGCTTAA GTGCGAA
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chromosome want to add gene to
Sticky ends Cut other DNA with same enzymes leave “sticky ends” on both can glue DNA together at “sticky ends” GTAACG AATTCACGCTT CATTGCTTAA GTGCGAA gene you want GGACCTG AATTCCGGATA CCTGGACTTAA GGCCTAT chromosome want to add gene to GGACCTG AATTCACGCTT CCTGGACTTAA GTGCGAA combined DNA
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Sticky ends help glue genes together
cut sites gene you want cut sites TTGTAACGAATTCTACGAATGGTTACATCGCCGAATTCACGCTT AACATTGCTTAAGATGCTTACCAATGTAGCGGCTTAAGTGCGAA AATTCTACGAATGGTTACATCGCCG GATGCTTACCAATGTAGCGGCTTAA isolated gene sticky ends AATGGTTACTTGTAACG AATTCTACGATCGCCGATTCAACGCTT TTACCAATGAACATTGCTTAA GATGCTAGCGGCTAAGTTGCGAA chromosome want to add gene to cut sites Recombinant DNA molecule DNA ligase joins the strands chromosome with new gene added TAACGAATTCTACGAATGGTTACATCGCCGAATTCTACGATC CATTGCTTAAGATGCTTACCAATGTAGCGGCTTAAGATGCTAGC sticky ends stick together
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How can bacteria read human DNA? human insulin gene in bacteria
Why mix genes together? Gene produces protein in different organism or different individual human insulin gene in bacteria TAACGAATTCTACGAATGGTTACATCGCCGAATTCTACGATC CATTGCTTAAGATGCTTACCAATGTAGCGGCTTAAGATGCTAGC aa “new” protein from organism ex: human insulin from bacteria bacteria human insulin
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The code is universal Since all living organisms… use the same DNA
use the same code book read their genes the same way Strong evidence for a single origin in evolutionary theory.
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Copy (& Read) DNA Transformation
insert recombinant plasmid into bacteria grow recombinant bacteria in agar cultures bacteria make lots of copies of plasmid “cloning” the plasmid production of many copies of inserted gene production of “new” protein transformed phenotype DNA RNA protein trait
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Grow bacteria…make more
transformed bacteria gene from other organism + recombinant plasmid vector plasmid grow bacteria harvest (purify) protein
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Uses of genetic engineering
Genetically modified organisms (GMO) enabling plants to produce new proteins Protect crops from insects: BT corn corn produces a bacterial toxin that kills corn borer (caterpillar pest of corn) Extend growing season: fishberries strawberries with an anti-freezing gene from flounder Improve quality of food: golden rice rice producing vitamin A improves nutritional value For example, a transgenic rice plant has been developed that produces yellow grains containing beta-carotene. Humans use beta-carotene to make vitamin A. Currently, 70% of children under the age of 5 in Southeast Asia are deficient in vitamin A, leading to vision impairment and increased disease rates.
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Transformed vertebrates
Green with envy?? Jelly fish “GFP” Transformed vertebrates
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Cut, Paste, Copy, Find… Word processing metaphor… cut paste copy find
restriction enzymes paste ligase copy plasmids bacterial transformation is there an easier way?? find ????
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STOP DAY 1 BIOTECH
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More Basic Biotechnology Tools
Sorting & Copying DNA
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Many uses of restriction enzymes…
Now that we can cut DNA with restriction enzymes… we can cut up DNA from different people… or different organisms… and compare it why? forensics medical diagnostics paternity evolutionary relationships and more…
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Can’t we just add those little marshmallows?
Comparing cut up DNA How do we compare DNA fragments? separate fragments by size How do we separate DNA fragments? run it through a gelatin agarose made from algae gel electrophoresis DNA jello?? Can’t we just add those little marshmallows?
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“swimming through Jello”
Gel electrophoresis A method of separating DNA in a gelatin-like material using an electrical field DNA is negatively charged when it’s in an electrical field it moves toward the positive side DNA – + “swimming through Jello”
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“swimming through Jello”
Gel electrophoresis DNA moves in an electrical field… so how does that help you compare DNA fragments? size of DNA fragment affects how far it travels small pieces travel farther large pieces travel slower & lag behind DNA – + “swimming through Jello”
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DNA & restriction enzyme
Gel Electrophoresis DNA & restriction enzyme - wells longer fragments power source gel shorter fragments + completed gel
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fragments of DNA separate out based on size
Running a gel cut DNA with restriction enzymes 1 2 3 Stain DNA ethidium bromide binds to DNA fluoresces under UV light
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Uses: Evolutionary relationships
Comparing DNA samples from different organisms to measure evolutionary relationships turtle snake rat squirrel fruitfly – 1 3 2 4 5 1 2 3 4 5 DNA +
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Uses: Medical diagnostic
Comparing normal allele to disease allele chromosome with normal allele 1 chromosome with disease-causing allele 2 allele 1 allele 2 – DNA Example: test for Huntington’s disease +
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Uses: Forensics Comparing DNA sample from crime scene with suspects & victim suspects crime scene sample S1 S2 S3 V – DNA +
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DNA fingerprints Comparing blood samples on defendant’s clothing to determine if it belongs to victim DNA fingerprinting comparing DNA banding pattern between different individuals ~unique patterns
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Differences at the DNA level
Why is each person’s DNA pattern different? sections of “junk” DNA doesn’t code for proteins made up of repeated patterns CAT, GCC, and others each person may have different number of repeats many sites on our 23 chromosomes with different repeat patterns GCTTGTAACGGCCTCATCATCATTCGCCGGCCTACGCTT CGAACATTGCCGGAGTAGTAGTAAGCGGCCGGATGCGAA GCTTGTAACGGCATCATCATCATCATCATCCGGCCTACGCTT CGAACATTGCCGTAGTAGTAGTAGTAGTAGGCCGGATGCGAA
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DNA patterns for DNA fingerprints
Allele 1 GCTTGTAACGGCCTCATCATCATTCGCCGGCCTACGCTT CGAACATTGCCGGAGTAGTAGTAAGCGGCCGGATGCGAA repeats cut sites Cut the DNA GCTTGTAACG GCCTCATCATCATCGCCG GCCTACGCTT CGAACATTGCCG GAGTAGTAGTAGCGGCCG GATGCGAA 1 2 3 – DNA + allele 1
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Differences between people
Allele 1 cut sites cut sites GCTTGTAACGGCCTCATCATCATTCGCCGGCCTACGCTT CGAACATTGCCGGAGTAGTAGTAAGCGGCCGGATGCGAA Allele 2: more repeats GCTTGTAACGGCCTCATCATCATCATCATCATCCGGCCTACGCTT CGAACATTGCCGGAGTAGTAGTAGTAGTAGTAGGCCGGATGCGAA 1 2 3 DNA fingerprint – DNA + allele 1 allele 2
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RFLPs Restriction Fragment Length Polymorphism
differences in DNA between individuals Alec Jeffries 1984 change in DNA sequence affects restriction enzyme “cut” site creates different fragment sizes & different band pattern
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RFLP / electrophoresis use in forensics
1st case successfully using DNA evidence 1987 rape case convicting Tommie Lee Andrews “standard” semen sample from rapist blood sample from suspect “standard” How can you compare DNA from blood & from semen? RBC? “standard” semen sample from rapist blood sample from suspect “standard”
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Electrophoresis use in forensics
Evidence from murder trial Do you think suspect is guilty? blood sample 1 from crime scene blood sample 2 from crime scene blood sample 3 from crime scene “standard” blood sample from suspect OJ Simpson blood sample from victim 1 N Brown blood sample from victim 2 R Goldman “standard”
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Uses: Paternity Who’s the father? – Mom F1 F2 child DNA +
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Making lots of copies of DNA
But it would be so much easier if we didn’t have to use bacteria every time…
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Copy DNA without plasmids? PCR!
Polymerase Chain Reaction method for making many, many copies of a specific segment of DNA ~only need 1 cell of DNA to start No more bacteria, No more plasmids, No more E. coli smelly looks!
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PCR process It’s copying DNA in a test tube! What do you need?
template strand DNA polymerase enzyme nucleotides ATP, GTP, CTP, TTP primer Thermocycler
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PCR primers The primers are critical!
need to know a bit of sequence to make proper primers primers can bracket target sequence start with long piece of DNA & copy a specified shorter segment primers define section of DNA to be cloned PCR is an incredibly versatile technique: An important use of PCR now is to “pull out” a piece of DNA sequence, like a gene, from a larger collection of DNA, like the whole cellular genome. You don’t have to go through the process of restriction digest anymore to cut the gene out of the cellular DNA. You can just define the gene with “flanking” primers and get a lot of copies in 40 minutes through PCR. Note: You can also add in a restriction site to the copies of the gene (if one doesn’t exist) by adding them at the end of the original primers. 20-30 cycles 3 steps/cycle 30 sec/step
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What does 90°C do to our DNA polymerase?
PCR process What do you need to do? in tube: DNA, DNA polymerase enzyme, primer, nucleotides denature DNA: heat (90°C) DNA to separate strands anneal DNA: cool to hybridize with primers & build DNA (extension) What does 90°C do to our DNA polymerase? play DNAi movie
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The polymerase problem
PCR cycles 3 steps/cycle 30 sec/step The polymerase problem Heat DNA to denature (unwind) it 90°C destroys DNA polymerase have to add new enzyme every cycle almost impractical! Need enzyme that can withstand 90°C… Taq polymerase from hot springs bacteria Thermus aquaticus Taq = Thermus aquaticus (an Archaebactera) Highly thermostable – withstands temperatures up to 95°C for more than 40min. BTW, Taq is patented by Roche and is very expensive. Its usually the largest consumable expense in a genomics lab. I’ve heard stories of blackmarket Taq clones, so scientists could grow up their own bacteria to produce Taq in the lab. It’s like pirated software -- pirated genes!
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Kary Mullis 1985 | 1993 development of PCR technique
a copying machine for DNA In 1985, Kary Mullis invented a process he called PCR, which solved a core problem in genetics: How to make copies of a strand of DNA you are interested in. The existing methods were slow, expensive & imprecise. PCR turns the job over to the very biomolecules that nature uses for copying DNA: two "primers" that flag the beginning & end of the DNA stretch to be copied; DNA polymerase that walks along the segment of DNA, reading its code & assembling a copy; and a pile of DNA building blocks that the polymerase needs to make that copy. As he wrote later in Scientific American: "Beginning with a single molecule of the genetic material DNA, the PCR can generate 100 billion similar molecules in an afternoon. The reaction is easy to execute. It requires no more than a test tube, a few simple reagents and a source of heat. The DNA sample that one wishes to copy can be pure, or it can be a minute part of an extremely complex mixture of biological materials. The DNA may come from a hospital tissue specimen, from a single human hair, from a drop of dried blood at the scene of a crime, from the tissues of a mummified brain or from a 40,000-year-old wooly mammoth frozen in a glacier."
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I’m a-glow! Got any Questions?
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