In this module, we will examine Explain what genetic · PDF fileIn this module, we will examine some of the techniques scientists have developed to study and 1 have developed to study

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Module 4B Module 4B –– BiotechnologyBiotechnology

In this module, we will examine In this module, we will examine some of the techniques scientists some of the techniques scientists have developed to study andhave developed to study and

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have developed to study and have developed to study and manipulate the DNA of living manipulate the DNA of living organisms.organisms.

Objective # 7Objective # 7

Explain what genetic Explain what genetic recombination is, why it is recombination is, why it is important and ho it occ rsimportant and ho it occ rs

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important, and how it occurs important, and how it occurs naturally.naturally.

Objective 7Objective 7

Genetic recombinationGenetic recombination involves involves combining DNA from 2 different combining DNA from 2 different sources into a single molecule. sources into a single molecule. Individual genes are not altered, Individual genes are not altered, h i l j i d h ih i l j i d h i

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they are simply joined together in they are simply joined together in new combinations.new combinations.Genetic recombination is Genetic recombination is

important because it produces new important because it produces new genetic types.genetic types.


New genetic types are the raw material New genetic types are the raw material for evolution. As new genetic types are for evolution. As new genetic types are generated, they may gradually replace generated, they may gradually replace existing genetic types by the process of existing genetic types by the process of

t r l l ti r b th r l ti rt r l l ti r b th r l ti r

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natural selection or by other evolutionary natural selection or by other evolutionary mechanisms.mechanisms.

Thus, the rate of evolution depends Thus, the rate of evolution depends directly on the rate at which new genetic directly on the rate at which new genetic types are generated.types are generated.


In nature, combining DNA from 2 In nature, combining DNA from 2 different individuals into a single different individuals into a single molecule involves 2 steps:molecule involves 2 steps:

first, DNA from 2 individuals is first, DNA from 2 individuals is

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combined in a single cellcombined in a single cell

then DNA from both individuals is then DNA from both individuals is joined to form a single moleculejoined to form a single molecule


In prokaryotes, several natural In prokaryotes, several natural mechanisms can combine DNA from mechanisms can combine DNA from 2 different individuals into a single cell:2 different individuals into a single cell:

TransformationTransformation a cell absorbs piecesa cell absorbs pieces

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Transformation Transformation –– a cell absorbs pieces a cell absorbs pieces of foreign DNA from its environment.of foreign DNA from its environment.

2

1

Genetic Recombination by transformation:Genetic Recombination by transformation:

Recipient Cell

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DNA 2Foreign

DNA

Recombinant DNA8


Plasmid uptakePlasmid uptake –– a cell absorbs a cell absorbs plasmids from the environment.plasmids from the environment.

TransductionTransduction –– a virus acts as a vector a virus acts as a vector to transfer pieces of foreign DNA to transfer pieces of foreign DNA from one cell to anotherfrom one cell to another

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from one cell to another.from one cell to another.ConjugationConjugation –– a temporary a temporary

cytoplasmic bridge connects 2 cells so cytoplasmic bridge connects 2 cells so that DNA can be passed from one cell that DNA can be passed from one cell to the other:to the other:

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Once pieces of foreign DNA have Once pieces of foreign DNA have entered a recipient cell, they often entered a recipient cell, they often combine with the recipient cell’s combine with the recipient cell’s

m t f rm r mbi t DNAm t f rm r mbi t DNA

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genome to form recombinant DNA.genome to form recombinant DNA.

Plasmids, for example, can be Plasmids, for example, can be integrated into, and excised from, integrated into, and excised from, specific locations on the main bacterial specific locations on the main bacterial genome: genome:

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3


In prokaryotes, genetic recombination In prokaryotes, genetic recombination generally occurs by transferring pieces generally occurs by transferring pieces of foreign DNA into a recipient cell and of foreign DNA into a recipient cell and then combining it with the recipient then combining it with the recipient

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cell’s genome.cell’s genome.

In most eukaryotes, recombination has In most eukaryotes, recombination has become a regular part of the lifecycle. become a regular part of the lifecycle. It occurs through fertilization followed It occurs through fertilization followed by crossing over during meiosis:by crossing over during meiosis:

Genetic Recombination in eukaryotes:Genetic Recombination in eukaryotes:

Fertilization

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Crossing Over


In order to recombine DNA from 2 In order to recombine DNA from 2 individuals through fertilization and individuals through fertilization and crossing over, the 2 individuals must crossing over, the 2 individuals must b bl t m t ith h th rb bl t m t ith h th r

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be able to mate with each other. be able to mate with each other. Therefore they must belong to the Therefore they must belong to the same species.same species.


Discuss the roles of restriction Discuss the roles of restriction enzymes and DNA ligase in enzymes and DNA ligase in constructing artificially recombinedconstructing artificially recombined

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constructing artificially recombined constructing artificially recombined DNA.DNA.


While various natural mechanisms can While various natural mechanisms can combine DNA from 2 individuals of the combine DNA from 2 individuals of the same species, scientists have developed same species, scientists have developed techniques to combine DNA from any 2 techniques to combine DNA from any 2

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q yq yindividuals.individuals.

These techniques result in the These techniques result in the production of production of artificially recombined artificially recombined DNADNA..


Two key enzymes are used to make Two key enzymes are used to make artificially recombined DNA.artificially recombined DNA.

1)1) Restriction enzymesRestriction enzymes (also called (also called restriction endonucleases):restriction endonucleases):

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cut DNA into fragments cut DNA into fragments –– so called so called “molecular scissors”“molecular scissors”

each one recognizes and cuts DNA each one recognizes and cuts DNA only where a specific sequence of only where a specific sequence of base pairs occurs. base pairs occurs.

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many do not cut straight through many do not cut straight through both strands, but make a jagged cut both strands, but make a jagged cut leaving unpaired bases at both ends. leaving unpaired bases at both ends. Because these unpaired bases can Because these unpaired bases can

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pair with complimentary bases, they pair with complimentary bases, they are called “sticky ends”.are called “sticky ends”.

2)2) DNA ligaseDNA ligase is used to join DNA is used to join DNA fragments together. This is the fragments together. This is the “molecular glue”.“molecular glue”.

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Summary of procedure for making Summary of procedure for making artificially recombined DNA:artificially recombined DNA:

Isolate DNA from 2 different sources.Isolate DNA from 2 different sources.

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Cut the DNA from both sources into Cut the DNA from both sources into fragments using the same restriction fragments using the same restriction enzyme.enzyme.


Mix the DNA fragments together. Mix the DNA fragments together. Because they were cut with the same Because they were cut with the same restriction enzyme, fragments from restriction enzyme, fragments from different sources will have the same different sources will have the same

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“sticky ends” and can pair up.“sticky ends” and can pair up.

Use the enzyme DNA ligase to join Use the enzyme DNA ligase to join the paired fragments together:the paired fragments together:


Recombinant DNA technology can be Recombinant DNA technology can be used to create used to create recombinant plasmidsrecombinant plasmids (or (or other recombinant agents such as other recombinant agents such as viruses) which are useful for inserting viruses) which are useful for inserting

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foreign genes into recipient cells.foreign genes into recipient cells.

Plasmids or other recombinant agents Plasmids or other recombinant agents that are used to insert foreign DNA that are used to insert foreign DNA into recipient cells are called into recipient cells are called vectorsvectors::

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Describe how the following can be Describe how the following can be used to produce multiple copies of a used to produce multiple copies of a DNA fragment:DNA fragment:

a)a) molecular cloning (gene cloning)molecular cloning (gene cloning)

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g g gg g g

b)b) polymerase chain reaction (PCR)polymerase chain reaction (PCR)


Why would scientists want to produce Why would scientists want to produce multiple copies of a DNA fragment?multiple copies of a DNA fragment?

to study its structure and functionto study its structure and function

to compare the fragment with DNA to compare the fragment with DNA

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to co pa e t e ag e t w t DNto co pa e t e ag e t w t DNfrom other sourcesfrom other sources

if it codes for a useful protein, to if it codes for a useful protein, to produce large quantities of the protein produce large quantities of the protein


a)a) molecular cloning (gene cloning)molecular cloning (gene cloning)

b)b) l h i i (PCR)l h i i (PCR)

There are 2 basic strategies for producing There are 2 basic strategies for producing multiple copies of a gene:multiple copies of a gene:

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b)b) polymerase chain reaction (PCR)polymerase chain reaction (PCR)

Objective 9aObjective 9a

a)a) WithWith gene cloning, gene cloning, a vector is used to a vector is used to insert the gene we wish to clone into insert the gene we wish to clone into a host cell. The host cell then a host cell. The host cell then replicates the foreign gene using the replicates the foreign gene using the

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same cellular machinery that it uses to same cellular machinery that it uses to replicate its own DNA.replicate its own DNA.

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During gene cloning, plasmids are During gene cloning, plasmids are often used as vectors to insert foreign often used as vectors to insert foreign genes into bacterial host cells.genes into bacterial host cells.

U i l id i h ifi iU i l id i h ifi i

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Using plasmids with specific genetic Using plasmids with specific genetic traits can help scientists determine traits can help scientists determine which bacterial cells have actually which bacterial cells have actually absorbed the gene we wish to clone:absorbed the gene we wish to clone:

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Summary of procedure for gene cloning:Summary of procedure for gene cloning:

Cut plasmids containing lac Z and amp Cut plasmids containing lac Z and amp resistance genes with a restriction resistance genes with a restriction enzyme. Use a restriction enzyme that enzyme. Use a restriction enzyme that

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cuts the plasmid once, inside the lac Z cuts the plasmid once, inside the lac Z gene.gene.

Use the same restriction enzyme to cut Use the same restriction enzyme to cut DNA containing the gene you wish to DNA containing the gene you wish to clone.clone.


Mix DNA from both sources together. Mix DNA from both sources together. Some plasmids will simply reclose. Other Some plasmids will simply reclose. Other plasmids will join with a piece of foreign plasmids will join with a piece of foreign DNA to form a recombinant plasmid.DNA to form a recombinant plasmid.

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Incubate bacterial cells with the plasmids. Incubate bacterial cells with the plasmids. Some cells will absorb no plasmid, some Some cells will absorb no plasmid, some will absorb a reclosed plasmid, and some will absorb a reclosed plasmid, and some will absorb a recombinant plasmid. will absorb a recombinant plasmid.


When plated on media containing When plated on media containing ampicillin and Xampicillin and X--gal, how do we know gal, how do we know which bacterial cells absorbed no which bacterial cells absorbed no plasmid?plasmid?

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These cells will not survive because These cells will not survive because they lack the gene for ampicillin they lack the gene for ampicillin resistance. Therefore no colonies are resistance. Therefore no colonies are formed.formed.


When plated on media containing When plated on media containing ampicillin and Xampicillin and X--gal, how do we know gal, how do we know which bacterial cells absorbed a which bacterial cells absorbed a reclosed (nonreclosed (non--recombinant) plasmid?recombinant) plasmid?

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These cells have a functional lacThese cells have a functional lac--Z Z gene. Therefore they will make the gene. Therefore they will make the enzyme enzyme ββ--galactosidase and will form galactosidase and will form blue colonies.blue colonies.


When plated on media containing When plated on media containing ampicillin and Xampicillin and X--gal, how do we know gal, how do we know which bacterial cells absorbed a which bacterial cells absorbed a recombinant plasmid? recombinant plasmid?

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The inserted foreign DNA will The inserted foreign DNA will inactivate the lacinactivate the lac--Z gene. Therefore Z gene. Therefore these cells do not make these cells do not make ββ--galactosidase galactosidase and will form white colonies.and will form white colonies.

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How do we know which white How do we know which white colonies contain the specific gene of colonies contain the specific gene of interest?interest?

The white colonies can be screened for The white colonies can be screened for

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the specific gene of interest using a the specific gene of interest using a genetic probegenetic probe. A genetic probe is a . A genetic probe is a radioactive molecule of RNA or radioactive molecule of RNA or singlesingle--stranded DNA that is stranded DNA that is complementary to the gene of interest.complementary to the gene of interest.

Film

Filter

1. Colonies of bacteria, each grownfrom cells taken from a white colony.

5. A comparison with the originalplate identifies the colonycontaining the gene.

2. A replica of the plateis made by pressinga filter against thecolonies. Some cellsfrom each colonyadhere to the filter.

Using a Genetic Probe to Screen for the Gene of Interest

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Film

3. The filter is washed with a solutionthat denatures the DNA and containsthe radioactively labeled probe. Theprobe contains nucleotide sequencescomplementary to the gene of interestand binds to cells containing the gene.

4. Only those coloniescontaining the gene willretain the probe and emitradioactivity on film placed over the filter.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Objective 9bObjective 9b

b)b) A second method for producing A second method for producing multiple copies of a gene is PCRmultiple copies of a gene is PCR

WithWith PCR, PCR, we create the we create the

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conditions needed for DNA conditions needed for DNA replication inside a test tube that replication inside a test tube that contains a copy of the gene:contains a copy of the gene:

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Summary of procedure for Summary of procedure for polymerase chain reactionpolymerase chain reaction (PCR):(PCR):

1)1) Denaturation Denaturation –– a solution containing a solution containing RNA primers and the DNA RNA primers and the DNA

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ppfragment to be amplified is heated so fragment to be amplified is heated so that the DNA dissociates into single that the DNA dissociates into single strands. strands.

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2)2) Annealing of primers Annealing of primers –– the solution the solution is cooled, and the primers bind to is cooled, and the primers bind to complementary sequences on the complementary sequences on the DNA flanking the gene to be DNA flanking the gene to be

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amplified.amplified.

3)3) Primer extension Primer extension –– DNA DNA polymerase then copies the polymerase then copies the remainder of each strand, beginning remainder of each strand, beginning at the primer.at the primer.


Repeat steps 1 Repeat steps 1 –– 3 many times, each 3 many times, each time doubling the number of copies, time doubling the number of copies, until a sufficient number of copies are until a sufficient number of copies are produced.produced.

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Explain the difference between Explain the difference between the following types of DNA the following types of DNA libraries:libraries:

a)a) Genomic librariesGenomic libraries

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a)a) Genomic librariesGenomic libraries

b)b) cDNA librariescDNA libraries


A A DNA libraryDNA library is a collection of DNA is a collection of DNA fragments representing all the DNA of fragments representing all the DNA of

r i mr i m

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an organism.an organism.


The simplest kind of DNA library is a The simplest kind of DNA library is a genomic librarygenomic library..

To create a genomic library, the entire To create a genomic library, the entire genome of an organism is fragmented. genome of an organism is fragmented.

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g g gg g gThe fragments are then inserted into a The fragments are then inserted into a vector, such as a plasmid or phage, and vector, such as a plasmid or phage, and introduced into a host:introduced into a host:

DNA fragmentsfrom source DNA

DNA insertedinto plasmid vector

DNA fragmentsfrom source DNA

DNA insertedinto phage vector

Plasmid Library Phage Library

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Each cell contains asingle fragment. All cellstogether are the library.

Each phage contains asingle fragment. All phage

together are the library.

Transformation Phages infect E. coli


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Another type of DNA library is a Another type of DNA library is a cDNA library.cDNA library.

A cDNA library includes only DNA A cDNA library includes only DNA fragments that actually code for fragments that actually code for

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ggproteins rather than all DNA proteins rather than all DNA fragments. This means that introns fragments. This means that introns and other nonand other non--coding sections of the coding sections of the genome are not included.genome are not included.


To produce a cDNA library, scientists To produce a cDNA library, scientists first isolate the first isolate the maturemature mRNA from an mRNA from an organism.organism.

An enzyme called An enzyme called reverse transcriptasereverse transcriptase

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ppis then used to make a complementary is then used to make a complementary DNA copy of each mature mRNA DNA copy of each mature mRNA molecule:molecule:

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If you want to make bacterial cells that If you want to make bacterial cells that can manufacture a particular human can manufacture a particular human protein, why is it important to insert protein, why is it important to insert cDNA rather than the original cDNA rather than the original

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genomic DNA into the bacterial cells?genomic DNA into the bacterial cells?


Explain how a DNA fragment Explain how a DNA fragment containing a particular containing a particular nucleotide sequence can be nucleotide sequence can be

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isolated and identified from a isolated and identified from a sample containing many sample containing many different DNA fragments.different DNA fragments.


A DNA fragment containing a A DNA fragment containing a particular nucleotide sequence can particular nucleotide sequence can be isolated and identified from a be isolated and identified from a sample containing many differentsample containing many different

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sample containing many different sample containing many different DNA fragments using a procedure DNA fragments using a procedure developed by E.M. Southern called developed by E.M. Southern called the Southern blot procedure:the Southern blot procedure:

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Explain the process and Explain the process and importance of RFLP analysis importance of RFLP analysis nd DNA fin rprintinnd DNA fin rprintin

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and DNA fingerprinting.and DNA fingerprinting.


As we have seen, As we have seen, restriction enzymesrestriction enzymescan be used to cut DNA into can be used to cut DNA into fragments called fragments called restriction fragmentsrestriction fragments..

However, these cuts are not made atHowever, these cuts are not made at

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However, these cuts are not made at However, these cuts are not made at random, each restriction enzyme cuts random, each restriction enzyme cuts the DNA only where a particular the DNA only where a particular sequence of bases occurs. These are sequence of bases occurs. These are called called recognition sitesrecognition sites..


If DNA from 2 individuals is different, If DNA from 2 individuals is different, then the location of recognition sites then the location of recognition sites for a particular restriction enzyme may for a particular restriction enzyme may also be different.also be different.

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If we cut DNA from both individuals If we cut DNA from both individuals with the same restriction enzyme, we with the same restriction enzyme, we may get different size fragments. may get different size fragments.

This is called a This is called a restriction fragment restriction fragment length polymorphismlength polymorphism (RFLP).(RFLP).


How can we determine the length of How can we determine the length of the fragments that are produced when the fragments that are produced when we treat DNA from 2 individuals with we treat DNA from 2 individuals with the same restriction enzyme?the same restriction enzyme?

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Gel ElectrophoresisGel Electrophoresis

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RFLP analysis is a powerful technique RFLP analysis is a powerful technique that is being in the field of forensics:that is being in the field of forensics:

small amounts of DNA collected at a small amounts of DNA collected at a crime scene can be amplified using PCRcrime scene can be amplified using PCR

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p gp g

the DNA is cut into fragments with a the DNA is cut into fragments with a restriction enzyme, and the fragments restriction enzyme, and the fragments are separated using gel electrophoresisare separated using gel electrophoresis


the resulting banding pattern is then the resulting banding pattern is then compared with the banding pattern compared with the banding pattern produced by DNA samples from produced by DNA samples from different suspectsdifferent suspects

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the banding pattern for each individual the banding pattern for each individual is essentially unique, and is referred to is essentially unique, and is referred to as a as a DNA fingerprintDNA fingerprint

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RFLPs can also be used to distinguish RFLPs can also be used to distinguish between DNA that contains different between DNA that contains different alleles if different recognition sites alleles if different recognition sites

r ithi r r l t thr ithi r r l t th

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occur within or very close to the occur within or very close to the different alleles.different alleles.

This is referred to as genetic screening:This is referred to as genetic screening:


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Explain the process and Explain the process and importance of DNA importance of DNA

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ppsequencing.sequencing.


DNA sequencingDNA sequencing involves determining involves determining the actual sequence of base pairs in a the actual sequence of base pairs in a DNA molecule.DNA molecule.

This is the ultimate level of genetic This is the ultimate level of genetic

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gganalysis.analysis.

A method of sequencing called A method of sequencing called enzymatic sequencingenzymatic sequencing was developed was developed by Fredrick Sangerby Fredrick Sanger


Sanger’s method uses modified Sanger’s method uses modified nucleotides called nucleotides called dideoxynucleotidesdideoxynucleotides..

Dideoxynucleotides have an H in place Dideoxynucleotides have an H in place of an OH at both the 2′ position and the of an OH at both the 2′ position and the 3′ position of the sugar As a result if a3′ position of the sugar As a result if a

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3 position of the sugar. As a result, if a 3 position of the sugar. As a result, if a dideoxynucleotide is incorporated into a dideoxynucleotide is incorporated into a growing nucleotide chain, no additional growing nucleotide chain, no additional nucleotides can be added and chain nucleotides can be added and chain elongation is terminated.elongation is terminated.

NH2

O

P–O O CH

NN

N

Dideoxynucleotides have an Dideoxynucleotides have an H in place of an OH at both H in place of an OH at both the 2′ position and the 3′ the 2′ position and the 3′ position of the sugar.position of the sugar.

P

O–

O O CH25´

4´

3´ 2´

1´

H H

O


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Describe at least 4 ways genetic Describe at least 4 ways genetic technology can be used for technology can be used for h b fih b fi

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human benefit.human benefit.

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1)1) Introduce genes coding for proteins Introduce genes coding for proteins with commercial or medical value into with commercial or medical value into other organisms, such as bacteria, in other organisms, such as bacteria, in order to mass produce the proteins. order to mass produce the proteins. Proteins produced in this way include:Proteins produced in this way include:

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Proteins produced in this way include:Proteins produced in this way include: Human insulin Human insulin –– helps regulate blood helps regulate blood

sugar levelsugar level Interferons Interferons –– assist the immune assist the immune

response by inhibiting viral replicationresponse by inhibiting viral replication


Human growth hormone Human growth hormone –– stimulates stimulates cell division and growthcell division and growth

Erythropoietin Erythropoietin –– stimulates red blood stimulates red blood cell productioncell production

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pp

Atrial peptides Atrial peptides –– may be a new way to may be a new way to treat high blood pressure and kidney treat high blood pressure and kidney failurefailure

Tissue plasminogen activator (TPA) Tissue plasminogen activator (TPA) ––dissolves blood clotsdissolves blood clots


2)2) Produce vaccines that provide Produce vaccines that provide protection against disease. Genetic protection against disease. Genetic technology has been used to develop technology has been used to develop two types of vaccines : subunit vaccines two types of vaccines : subunit vaccines and DNA vaccines.and DNA vaccines.

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N vN v A A subunit vaccinesubunit vaccine is developed using a is developed using a

small portion (or subunit) of the small portion (or subunit) of the pathogen pathogen -- for example, a protein in the for example, a protein in the coat or envelope that surrounds a coat or envelope that surrounds a harmful virus.harmful virus.


To prepare a subunit vaccine against a To prepare a subunit vaccine against a harmful virus, a gene coding for a harmful virus, a gene coding for a protein in the coat or envelope of the protein in the coat or envelope of the harmful virus is spliced into theharmful virus is spliced into the

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harmful virus is spliced into the harmful virus is spliced into the genome of a harmless virus like genome of a harmless virus like vaccinia. vaccinia.


Next, the modified vaccinia virus, Next, the modified vaccinia virus, which contains surface proteins from which contains surface proteins from the harmful virus, is injected into the harmful virus, is injected into uninfected people. uninfected people.

The immune system detects theThe immune system detects the

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The immune system detects the The immune system detects the proteins from the harmful virus on the proteins from the harmful virus on the surface of vaccinia and makes surface of vaccinia and makes antibodies against any virus with those antibodies against any virus with those proteins.proteins.

Gene specifying herpessimplex surface protein

Herpes simplex virus

2. Herpes simplexgene is isolated.

3. Vaccinia DNA is extracted and cleaved.

1. DNA is extracted.

Construction of a subunit vaccine against herpes simplex:

78Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Human immuneresponse

Harmless vaccinia(cowpox) virus

4. Fragment containingsurface gene combines with cleaved vaccinia DNA.

5. Harmless engineered virus (the vaccine) with surface like herpes simplex is injected into the human body.

6. Antibodies directedagainst herpes simplex viral coat are made.

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To prepare a To prepare a DNA vaccineDNA vaccine, a gene , a gene from a pathogen is artificially replicated from a pathogen is artificially replicated and then injected directly into and then injected directly into uninfected people. If human cells take uninfected people. If human cells take

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up the gene, some may use it to make up the gene, some may use it to make the protein encoded by the gene. the protein encoded by the gene.

The presence of the foreign protein in The presence of the foreign protein in the body triggers an immune response the body triggers an immune response against the pathogen.against the pathogen.


Unlike subunit vaccines, DNA Unlike subunit vaccines, DNA vaccines do not stimulate the vaccines do not stimulate the production of antibodies against the production of antibodies against the pathogen. Instead, they stimulate the pathogen. Instead, they stimulate the

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activity of killer Tactivity of killer T--cells, which are cells, which are another component of the body’s another component of the body’s immune response.immune response.

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3)3) Alter the human genome to cure Alter the human genome to cure genetic disease or give people genetic disease or give people certain desirable traits.certain desirable traits.

Many genetic disorders are caused Many genetic disorders are caused

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y gy gby a single defective allele.by a single defective allele.

In In gene therapygene therapy, scientists try to , scientists try to supply a copy of the normal allele to supply a copy of the normal allele to those cells that need it but lack it.those cells that need it but lack it.

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There are some serious obstacles to There are some serious obstacles to successful gene therapy:successful gene therapy:

How do you get a copy of the gene How do you get a copy of the gene into enough of the cells that need it?into enough of the cells that need it?

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Will the gene function normally once it Will the gene function normally once it is inserted into a cell?is inserted into a cell?

Will inserting a new gene into a cell Will inserting a new gene into a cell damage or alter the expression of any damage or alter the expression of any other genes?other genes?

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During gene therapy, there is always During gene therapy, there is always the concern that insertion of a normal the concern that insertion of a normal allele into a cell could inactivate allele into a cell could inactivate another essential gene or turn on a another essential gene or turn on a

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gene inappropriately.gene inappropriately.

Gene therapy was first used Gene therapy was first used successfully to treat SCID (severe successfully to treat SCID (severe combined immunodeficiency).combined immunodeficiency).


The procedure involved removing The procedure involved removing white blood cells from the patient, white blood cells from the patient, using a virus to insert the necessary using a virus to insert the necessary gene into the cells, and then returning gene into the cells, and then returning

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the cells to the bloodstream.the cells to the bloodstream.

Although the treatment was successful, Although the treatment was successful, about 15% of patients developed a about 15% of patients developed a rare form of leukemia.rare form of leukemia.


Scientists determined that the vector Scientists determined that the vector used to introduce the normal allele used to introduce the normal allele into white blood cells integrated into into white blood cells integrated into the genome next to a protothe genome next to a proto--oncogene oncogene

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called LM02.called LM02.

Activation of this gene caused the Activation of this gene caused the leukemias.leukemias.


4)4) Genetically alter organisms, including Genetically alter organisms, including crops and livestock, to give them certain crops and livestock, to give them certain desirable traits such as disease desirable traits such as disease resistance, frost resistance, faster growth resistance, frost resistance, faster growth

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rate, or higher nutritional valuerate, or higher nutritional value. . Organisms that have genes introduced Organisms that have genes introduced

without the use of conventional without the use of conventional breeding are called breeding are called transgenictransgenic::

Daffodil

Ferritin geneis transferredinto rice frombeans.

Phytase gene istransferred intorice from afungus.

Metallothioningene istransferred intorice from wildrice.

Enzymes for-carotenesynthesis aretransferred intorice from daffodils.

Beans Aspergillus fungus Wild riceTransgenic Rice

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Fe Pt SRicechromosome

A1

Ferritin proteinincreases ironcontent of rice.

Phytate, whichinhibits ironreabsorption,is destroyed by thephytase enzyme.

Metallothioninprotein suppliesextra sulfur toincrease ironuptake.

-carotene, aprecursor tovitamin A, issynthesized.

A2 A3 A4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 90

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Discuss some potential problems Discuss some potential problems associated with genetic technology.associated with genetic technology.

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1)1) Some question the safety of eating Some question the safety of eating genetically modified organisms. So genetically modified organisms. So far, no negative effects have been far, no negative effects have been documented.documented.

2)2) Some worry that genes fromSome worry that genes from

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2)2) Some worry that genes from Some worry that genes from genetically modified organisms may genetically modified organisms may spread into the gene pools of wild spread into the gene pools of wild organisms and modify them. There organisms and modify them. There is no evidence this has occurred.is no evidence this has occurred.


3)3) Another concern is that genetically Another concern is that genetically altered organisms may escape into altered organisms may escape into the environment and replace natural the environment and replace natural organisms or upset the balance of organisms or upset the balance of naturenature

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nature.nature.4)4) There are also moral and ethical There are also moral and ethical

questions associated with controlling questions associated with controlling the genetic makethe genetic make--up and evolution up and evolution of existing life forms, including of existing life forms, including humans.humans.

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In this module, we will examine Explain what genetic · PDF fileIn this module, we will examine some of the techniques scientists have developed to study and 1 have developed to study