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Biotechnology andGenetic Engineering
AP Biology Chapter 20
Terminology
• Genetic engineering – direct manipulation of genetic material for practical purposes
• Biotechnology – use of living organisms or their components to make products for us
• Recombinant DNA – combining pieces of DNA from different organisms
• Gene cloning – making copies of DNA
Making recombinant DNA
• Plasmids (small circular pieces of DNA in bacterial cells) are used to insert pieces of foreign DNA
The DNA is cut using restriction enzymes
What are restriction enzymes?
• Restriction enzymes come from bacteria and recognize a particular pattern of DNA, often 4, 6 or 8 base pairs long, and then cut the DNA within this recognized sequence.
• Bacteria use these enzymes to kill off other competing bacteria by cutting up their DNA.
How do they cut?
STICKY ENDS BLUNT ENDS
ACT GAA TTC CGG AAT GAA TTC
TGA CTT AAG GCC TTA CTT AAG
Where would the enzyme EcoRI cut?
ACT GAA TTC CGG AAT GAA TTC
TGA CTT AAG GCC TTA CTT AAG
There would be three pieces: one 4 bases, one 12 bases, and one 5 bases.
How do bacteria protect it’s own DNA from being cut by
the enzymes?
It methylates it’s own DNA.
Making recombinant DNA in plasmids
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/steps_in_cloning_a_gene.html
http://www.nearingzero.net/natural/screenres/natural039.jpg
Bacterial plasmids often contain antibiotic resistance genes.
Genes can be cloned into
vectors such as plasmids
Fig. 20-2
DNA of chromosome
Cell containing geneof interest
Gene inserted intoplasmid
Plasmid put intobacterial cell
RecombinantDNA (plasmid)
Recombinantbacterium
Bacterialchromosome
Bacterium
Gene ofinterest
Host cell grown in cultureto form a clone of cellscontaining the “cloned”gene of interest
Plasmid
Gene ofInterest
Protein expressedby gene of interest
Basic research andvarious applications
Copies of gene Protein harvested
Basicresearchon gene
Basicresearchon protein
Gene for pest resistance inserted into plants
Gene used to alter bacteria for cleaning up toxic waste
Protein dissolvesblood clots in heartattack therapy
Human growth hor-mone treats stuntedgrowth
2
4
1
3
Fig. 20-2a
DNA of chromosome
Cell containing geneof interest
Gene inserted intoplasmid
Plasmid put intobacterial cell
RecombinantDNA (plasmid)
Recombinantbacterium
Bacterialchromosome
Bacterium
Gene ofinterest
Plasmid
2
1
2
Fig. 20-2b
Host cell grown in cultureto form a clone of cellscontaining the “cloned”gene of interest
Gene ofInterest
Protein expressedby gene of interest
Basic research andvarious applications
Copies of gene Protein harvested
Basicresearchon gene
Basicresearchon protein
4
Recombinantbacterium
Gene for pest resistance inserted into plants
Gene used to alter bacteria for cleaning up toxic waste
Protein dissolvesblood clots in heartattack therapy
Human growth hor-mone treats stuntedgrowth
3
Fig. 20-4-1
Bacterial cell
Bacterial plasmid
lacZ gene
Hummingbird cell
Gene of interest
Hummingbird DNA fragments
Restrictionsite
Stickyends
ampR gene
TECHNIQUE
Fig. 20-4-2
Bacterial cell
Bacterial plasmid
lacZ gene
Hummingbird cell
Gene of interest
Hummingbird DNA fragments
Restrictionsite
Stickyends
ampR gene
TECHNIQUE
Recombinant plasmids
Nonrecombinant plasmid
Fig. 20-4-3
Bacterial cell
Bacterial plasmid
lacZ gene
Hummingbird cell
Gene of interest
Hummingbird DNA fragments
Restrictionsite
Stickyends
ampR gene
TECHNIQUE
Recombinant plasmids
Nonrecombinant plasmid
Bacteria carryingplasmids
Fig. 20-4-4
Bacterial cell
Bacterial plasmid
lacZ gene
Hummingbird cell
Gene of interest
Hummingbird DNA fragments
Restrictionsite
Stickyends
ampR gene
TECHNIQUE
Recombinant plasmids
Nonrecombinant plasmid
Bacteria carryingplasmids
RESULTS
Colony carrying non-recombinant plasmidwith intact lacZ gene
One of manybacterialclones
Colony carrying recombinant plasmid with disrupted lacZ gene
Steps
1. Plasmid and DNA of gene of interest are isolated.
2. Both DNAs are cut with the same restriction enzyme.
3. “new” DNA is ligated into plasmid4. Recombinant plasmids are inserted
into bacterial cells.5. Plate bacteria on agar. Bacteria will
express new genes.
Plasmid Maps
Plasmid MapsSometimes called restriction maps are graphical
representation of plasmids, that show the locations of major identifiable landmarks on DNA like restriction enzyme sites, genes of interest, plasmid length etc.
The collection of thousands of clones of bacteria containing recombinant plasmids is called a genomic library.
• In molecular biology, plasmid (or restriction) maps are used as a reference to engineer plasmids.
• The plasmids are digested by enzymes chosen and the resulting samples are subsequently run on an electrophoresis gel.
Our experiment: to transform E.coli with pGLO plasmid containing the jellyfish gene GFP to make them have the ability to glow
• To isolate only the cells containing the pGLO DNA, the plasmid contains the beta-lactamase gene which encodes for an ampicillin resistance (Ampr) protein.
• After the transformation, the cells are grown on a solid medium called an agar plate. This medium will contain the antibiotic ampicillin.
• In the presence of the ampicillin, only the bacteria containing the pGLO plasmid will have the Ampr protein which will break down the antibiotic, and be able to grow.
• This process is called antibiotic selection.
GFP results in E.coli
This plate shows bacteria expressing six different types of flourescent proteins
GRP has been used as tracers to see if the plasmid has been taken up by
the bacteria.
How much does it cost to make a transgenic mouse?
• Transgenic Mouse Production: The current fee for transgenic mouse production for UTMB
• investigators is $4000 (for 3 days of injections into [C57BL/6 X C3H/He]F2 embryos) or $5200
• (for 4 days of injection into C57BL/6 or FVB/N embryos; $1250 for each additional day
Storing Cloned Genes in DNA Libraries
• Plasmid libraries containing genes of interest cloned in
• Phage library that is made using bacteriophages which store genes of interest
Fig. 20-5a
Bacterial clones
Recombinantplasmids
Recombinantphage DNA
or
Foreign genomecut up withrestrictionenzyme
(a) Plasmid library (b) Phage library
Phageclones
Viruses used
as vectors
• BACs (bacterial artificial chromosome) are another type of vector used in DNA library construction
• A bacterial artificial chromosome (BAC) is a large plasmid that has been trimmed down and can carry a large DNA insert
Fig. 20-5
Bacterial clones
Recombinantplasmids
Recombinantphage DNA
or
Foreign genomecut up withrestrictionenzyme
(a) Plasmid library (b) Phage library (c) A library of bacterial artificial chromosome (BAC) clones
Phageclones
Large plasmidLarge insertwith many genes
BACclone
• A complementary DNA (cDNA) library is made by cloning DNA made in vitro by reverse transcription of all the mRNA produced by a particular cell
• A cDNA library represents only part of the genome—only the subset of genes transcribed into mRNA in the original cells
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/cdna.html
Fig. 20-6-1
DNA innucleus
mRNAs in cytoplasm
Fig. 20-6-2
DNA innucleus
mRNAs in cytoplasm
Reversetranscriptase Poly-A tail
DNAstrand
Primer
mRNA
Fig. 20-6-3
DNA innucleus
mRNAs in cytoplasm
Reversetranscriptase Poly-A tail
DNAstrand
Primer
mRNA
DegradedmRNA
Fig. 20-6-4
DNA innucleus
mRNAs in cytoplasm
Reversetranscriptase Poly-A tail
DNAstrand
Primer
mRNA
DegradedmRNA
DNA polymerase
Fig. 20-6-5
DNA innucleus
mRNAs in cytoplasm
Reversetranscriptase Poly-A tail
DNAstrand
Primer
mRNA
DegradedmRNA
DNA polymerase
cDNA
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/fish.html
Ways to introduce
new genes into bacteria.
Conjugation – through tubes between bacteria Transformation – negative DNA taken upTransduction by bacteriophages or other virusesMutation
ALL of these introduce GENETIC VARIATION!
Nucleic Acid Hybridization
• Used to detect genes
• The DNA of the cell is denatured to produce single stranded DNA.
• The radioactive probe will hybridize (bond) with complementary bases if present.
• Probes can be radioactive isotopes or
flourescent dyes.
The radioactive probe is made by determining a short segment of the protein sequence, then "back translating" to the possible short DNA sequences called oligomers.
Then these DNA oligomers (known as "oligos") are radiolabeled, and applied to the blotted clones.
They should hybridize only to clones containing sequence encoding the desired protein.
How does this work?• Protein segment
gly – gly – ser – glutamic acid
• Look on Genetic Codon chart, find mRNA codons
GGU – GGU – UCU – GAA
• Make a radioactive DNA
(oligos)probe
CCA – CCA – AGA - CTT
Expression of eukaryoticgenes in prokaryotes
• Use an expression vector with a prokaryotic promoter upstream from the location of the gene (ie operon)
• Create artificial genes without introns since bacteria do not have the machinery for eliminating introns.
• YACS
What are YACS?
• Yeast artificial chromosomes that carry foreign DNA.
• Yeast cells have plasmids that can act as vectors.
Electroporation
• injecting DNA into eukaryotic cells
PCR Polymerase Chain Reaction
• Used to amplify DNA
• Discovered by Kary Mullis (GT grad)
A Thermocycler
Steps of PCR?
• Denature DNA (94-96 C)
• Anneal (base pair) primers (50 – 65 C)
• Extend primers (72 for polymerase to work)
• Machines called thermocyclers do this.
http://www.dnalc.org/ddnalc/resources/shockwave/pcranwhole.html
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/polymerase_chain_reaction.html
Fig. 20-8b
Cycle 1yields
2molecules
Denaturation
Annealing
Extension
Primers
Newnucleo-tides
3 5
3
2
5 31
Fig. 20-85
Genomic DNA
TECHNIQUE
Cycle 1yields
2molecules
Denaturation
Annealing
Extension
Cycle 2yields
4molecules
Cycle 3yields 8
molecules;2 molecules
(in whiteboxes)
match targetsequence
Targetsequence
Primers
Newnucleo-tides
3
3
3
3
5
5
51
2
3
• In PCR, a heat-stable DNA polymerase is used, most commonly Taq Polymerase from the thermophilic microbe Thermus aquaticus.
• Thomas Brock discovered T. aquaticus from a hot spring at Yellowstone National Park.
Applications of PCR
PCR has replaced cloning for many purposes, particularly the sequencing of DNA.
• It is faster and requires no vectors, which can mutate as they reproduce.
• It can be used forensically, to amplify tiny amounts of DNA from criminal evidence; or clinically, to detect DNA sequences linked to inherited disorders.
What is gel electrophoresis?
• A technique to separate DNA based on the movement of DNA fragments from neg to pos (DNA is neg).
• Smaller fragments travel farther.
• Samples are placed in gels.
Gel Electrophoresis
Southern Blotting“DNA Fingerprinting”- named for Edwin Southern- used to identify DNA fragments
1. Isolate DNA2.Cut DNA into fragments with restriction enzymes.3.Electrophorese.4.Blot onto nylon membrane.5.Apply radioactive probes.6.Wash to remove unbonded probes.
http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter14/animation_quiz_5.html
In DNA fingerprinting
• Single nucleotide polymorphisms (SNPs) are useful genetic markers
• These are single base-pair sites that vary in a population (most of our DNA is identical
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/restriction_fragment_length_polymorphisms.html
Fig. 20-21
Disease-causingallele
DNA
SNP
Normal alleleT
C
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/video_quiz_-_world_trade_center_dna.html
Many genetic diseases are the result of a
polymorphism at a single locus.
• When a restriction enzyme is added, SNPs result in DNA fragments with different lengths, or restriction fragment length polymorphisms (RFLP)
• Some polymorphisms cause disease, while some do not. Others indicate a predisposition to disease.
Hemoglobin S is missing a restriction site due to a polymorphism
RFLP Analysis in Paternity Cases
RFLP Analysis in Paternity Cases
Short Tandem Repeats• Even more sensitive is the use of
genetic markers called short tandem repeats (STRs), which are variations in the number of repeats of specific DNA sequences
• The Human Genome Project has shown that there are tens of thousands of STR loci in human DNA.
• An individual inherits one copy of an STR from each parent,
D7S280 is one of the 13 core CODIS STR genetic loci. This DNA is found on human chromosome 7. The DNA sequence of a representative allele of this locus is shown below. The tetrameric repeat sequence of D7S280 is "gata". Different alleles of this locus have from 6 to 15 tandem repeats of the "gata" sequence. How many tetrameric repeats are present in the DNA sequence shown below?
1 aatttttgta ttttttttag agacggggtt tcaccatgtt ggtcaggctg actatggagt 61 tattttaagg ttaatatata taaagggtat gatagaacac ttgtcatagt ttagaacgaa121 ctaacgatag atagatagat agatagatag atagatagat agatagatag atagacagat181 tgatagtttt tttttatctc actaaatagt ctatagtaaa catttaatta ccaatatttg241 gtgcaattct gtcaatgagg ataaatgtgg aatcgttata attcttaaga atatatattc301 cctctgagtt tttgatacct cagattttaa ggcc
If the genotypes of both parents are known, we use a Punnett Square to predict the possible phenotypes of their offspring. Each child inherits one allele of a given locus from each parent. Panel (a) - At the D21S11 locus, the children of Bob Blackett and wife
Anne can have four different genotypes. Son David is 28, 31. Daughter Katie is 29, 30. Panel (b) - Bob Blackett inherited the 31 allele from his mother, Norma. Therefore the 29 allele is paternal.
If Bob's paternal was not 29, what would be your conclusion?
Huntington’s Disease can be diagnosed by the number of CAG repeats
The data below shows the results of electrophoresis of PCR fragments amplified using probes for the site which has been shown to be altered in Huntington's
disease. The male parent, as shown by the black box, got Huntington's disease when he was 40 years old. His children include 6 (3,5,7,8,10,11) with Huntington's disease, and the age at which the symptoms first began is shown by the number
above the band from the PCR fragment.
What is the prognosis for
the normal children 4, 6,
and 9?
Sanger Sequencing
• Used to sequence short segments of DNA• Single-stranded fragments are incubated
with fluorescent-tagged short segments for DNA hybridization.
• When fragments hybridize with the tagged nucleotide, the hybridization stops.
• Fragments are electrophoresed and analyzed.
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/sanger_sequencing.html
Analyzing Expression of Genes
• Northern Blotting – using radioactive probes to look for mRNA being produced
• RT-PCR – Reverse transcriptase-polylmerase chain reaction – makes cDNA from mRNAs and then PCRs the DNA for electrophoresis
• in situ hybridization – can locate specific mRNA’s in cells
• Micro – arrays - Isolate mRNA from cells, make cDNA using reverse transcriptase, then uses cDNA to explore collections of genomic DNA to see if they hybridize
http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter18/using_a_dna_microarray.html
• Microarrays are useful in discerning gene expression in different tissues AND at different stages of development.
• Different brightness and
colors signify rates of
expression.
Google Image Result for http://www.g2conline.info/content/1178/1
178_what_microarray_thumb.jpg
http://www.dnalc.org/resources/3d/26-microarray.html
An example
DNA Microarray Methodology Animation
Determining Gene Function
• In vitro mutagenesis – changes made to cloned gene, gene returned to cell and it “knocks out” the normal gene. Then look for abnormalities.
• RNA interference (RNAi) – uses RNA to block translation of mRNA and see what happens.
Cloning Organisms
• Organismal cloning – producing genetically identical individuals from a single somatic cell of a multicellular organism
In plants• Steward demonstrated
genomic equivalence in plants by growing carrot plants from differentiated root cells.
• Most plant cells remain totipotent, retaining the ability to give rise to a complete new organisms.
In Animals
• Briggs and all transplanted nuclei from embryonic frog cells into enucleated egg cells and produced cloned frogs
• Nuclear transplantation – name of process
• Whether normal development occurred depended on developmental age of the transplanted nucleus.
Fig. 20-17
EXPERIMENT
Less differ-entiated cell
RESULTS
Frog embryo Frog egg cell
UV
Donornucleustrans-planted
Frog tadpole
Enucleated egg cell
Egg with donor nucleus activated to begin
development
Fully differ-entiated(intestinal) cell
Donor nucleus trans-planted
Most developinto tadpoles
Most stop developingbefore tadpole stage
Nuclear Transplantation
And then Dolly came along in 1997
Fig. 20-18
TECHNIQUE
Mammarycell donor
RESULTS
Surrogatemother
Nucleus frommammary cell
Culturedmammary cells
Implantedin uterusof a thirdsheep
Early embryo
Nucleusremoved
Egg celldonor
Embryonicdevelopment Lamb (“Dolly”)
genetically identical tomammary cell donor
Egg cellfrom ovary
Cells fused
Grown inculture
1
33
4
5
6
2
Why Dolly died young 6 yrs
• Dolly's telomeres were found to be approximately 80% of the length they should be for a sheep her age.
• Also there is the concern of damaged DNA being carried into the clone
Cloned animals do not look exactly like the transplanted nucleus due to cytoplasmic affects.
RainbowCC
CC and her Surrogate mom
Hi Mrs. Smith!
• In most nuclear transplantation studies, only a small percentage of cloned embryos have developed normally to birth
• Many epigenetic changes, such as acetylation of histones or methylation of DNA, must be reversed in the nucleus from a donor animal in order for genes to be expressed or repressed appropriately for early stages of development
Stem Cells
• Relatively unspecialized cells that continue to reproduce themselves and can be induced to form specialized cells
• Embryonic cells are more totipotent than adult stem cells
http://cbm.msoe.edu/stupro/so/SOStemCellVideo2010.html
• Therapeutic cloning – using stem cells to replace organs and tissues
• Reproductive cloning – using stem cells to reproduce new organisms
• Both raise ethical
debates
Research points to a new direction in Stem Cell Research
InducedPluripotentStem Cells
The Nobel Prize in Medicine 2012 was awarded to two biologists for their breakthroughs in the field of stem-cell research — two discoveries that happened 44 years apart. The honors go to Britain's Sir John B. Gurdon and Japan's Shinya Yamanaka for their pioneering work with the life-shaping cells, which can be reprogrammed to create any kind of tissue in the body.
Benefits of DNA technology
• Medical Applications
• identification of human genes in which mutation plays a role in genetic diseases
Huntington’s Disease can be diagnosed by the number of CAG repeats
The data below shows the results of electrophoresis of PCR fragments amplified using probes for the site which has been shown to be altered in Huntington's
disease. The male parent, as shown by the black box, got Huntington's disease when he was 40 years old. His children include 6 (3,5,7,8,10,11) with Huntington's disease, and the age at which the symptoms first began is shown by the number
above the band from the PCR fragment.
What is the prognosis for
the normal children 4, 6,
and 9?
Human Gene Therapy
• Gene therapy is the alteration of an afflicted individual’s genes
• Vectors, such as viruses, are used for delivery of genes into specific types of cells, for example bone marrow
• It may be difficult to target cells.• Gene therapy raises ethical questions,
such as whether human germ-line cells should be treated to correct the defect in future generations
Fig. 20-22
Bonemarrow
Clonedgene
Bonemarrowcell frompatient
Insert RNA version of normal alleleinto retrovirus.
Retroviruscapsid
Viral RNA
Let retrovirus infect bone marrow cellsthat have been removed from thepatient and cultured.
Viral DNA carrying the normalallele inserts into chromosome.
Inject engineeredcells into patient.
1
2
3
4
Pharmaceutical Products
• Advances in DNA technology and genetic research are important to the development of new drugs to treat diseases
• In particular “pharm” animals and plants can be used to produce certain products
Fig. 20-23
Forensic Evidence and Genetic Profiles
• An individual’s unique DNA sequence, or genetic profile, can be obtained by analysis of tissue or body fluids
Fig. 20-24This photo shows EarlWashington just before his release in 2001,after 17 years in prison.
These and other STR data exonerated Washington andled Tinsley to plead guilty to the murder.
(a)
Semen on victim
Earl Washington
Source of sample
Kenneth Tinsley
STRmarker 1
STRmarker 2
STRmarker 3
(b)
17, 19
16, 18
17, 19
13, 16 12, 12
14, 15 11, 12
13, 16 12, 12
Environmental Cleanup
• Some modified microorganisms can be used to extract minerals from the environment or degrade potentially toxic waste materials
• Biofuels make use of crops such as corn, soybeans, and cassava to replace fossil fuels
Genetic Engineering in Plants
• Agricultural scientists have endowed a number of crop plants with genes for desirable traits
• The Ti plasmid is the most commonly used vector for introducing new genes into plant cells
Is this safe?
• Most public concern about possible hazards centers on genetically modified (GM) organisms used as food
• Some are concerned about the creation of “super weeds” from the transfer of genes from GM crops to their wild relatives
Fig. 20-25
Site whererestrictionenzyme cuts
T DNA
Plant with new trait
Tiplasmid
Agrobacterium tumefaciens
DNA withthe geneof interest
RecombinantTi plasmid
TECHNIQUE
RESULTS
• Guidelines are in place in the United States and other countries to ensure safe practices for recombinant DNA technology