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  1. 1. Biotechnology The New Frontier
  2. 2. Recombinant DNA <ul><li>Developed in the 1970’s at Stanford University </li></ul><ul><li>Researchers showed that genetic traits could be transferred from one organism to another </li></ul><ul><li>The DNA of one microorganism recombined with the inserted DNA sequence of another </li></ul><ul><li>The host DNA could thus be edited to exhibit a specific modification </li></ul><ul><li>This process is similar to editing a written text: </li></ul><ul><ul><li>scissors and &quot;glue&quot; are used to &quot;cut&quot; and &quot;paste.&quot; </li></ul></ul><ul><li>This process can be used to produce many protein products of medical and economic importance </li></ul>
  3. 3. The Insulin Example <ul><li>The gene for insulin production in humans could be cut and then pasted into the DNA of E. coli, a bacterium that inhabits the human digestive tract. </li></ul><ul><li>Bacterial cells divide rapidly making billions of copies </li></ul><ul><li>Bacteria can be raised in a laboratory in tissue culture media. </li></ul><ul><li>Each bacterium carries in its DNA a replica of the gene for insulin production. </li></ul><ul><ul><li>Each new E. coli cell has inherited the human insulin gene “sentence.” </li></ul></ul><ul><li>Human insulin is produced by the bacteria and can be harvested from the growth medium </li></ul>
  4. 4. Transferring Genes <ul><li>How do we transfer the gene carrying the instructions for insulin production? </li></ul><ul><li>One method is to cut the gene from human DNA and paste, or splice, it into plasmid DNA </li></ul><ul><ul><li>Plasmids are a special type of bacterial DNA that takes a circular form and can be used as a vehicle for this editing job. </li></ul></ul><ul><li>Our &quot;scissors&quot; are the class of enzymes called restriction enzymes . </li></ul>
  5. 5. Restriction Enzymes <ul><li>Also called restriction endonucleases </li></ul><ul><li>There are over a hundred restriction enzymes </li></ul><ul><li>Each enzymes cuts in a very precise way at a specific base sequence of the DNA molecule. </li></ul><ul><li>With these “scissors” used singly or in various combinations, the segment of the human DNA molecule that specifies insulin production can be isolated. </li></ul>
  6. 7. Production of Recombinant DNA <ul><li>This excised segment of DNA is &quot;glued&quot; into place using the enzyme DNA ligase. </li></ul><ul><li>The result is an edited, or recombinant , DNA molecule. </li></ul>
  7. 10. Cloning a Human Gene <ul><li>This is a highly simplified description of rDNA technology </li></ul><ul><li>A recombinant bacterial plasmid can be created carrying the gene of interest </li></ul>
  8. 11. Forming a Recombinant Plasmid <ul><li>When this recombinant plasmid DNA is inserted into E. coli, the cell will be able to process the instructions to assemble the amino acids for insulin production. </li></ul>
  9. 12. Gene Cloning <ul><li>These new instructions are now passed along to the next generation of E. coli cells </li></ul><ul><ul><li>This process known as gene cloning . </li></ul></ul>
  10. 13. Molecular “Searching” Techniques <ul><li>Techniques for analyzing DNA, RNA, and protein. </li></ul><ul><li>Molecular searches use one of several forms of complimentarity to identify target macromolecules among a large number of other molecules. </li></ul><ul><li>Major Techniques include: </li></ul><ul><li>Southerns blots, </li></ul><ul><li>Northern blots </li></ul><ul><li>Western blots </li></ul><ul><li>Cloning </li></ul>
  11. 14. Techniques <ul><li>Southern Blot </li></ul><ul><ul><li>DNA cut with restriction enzymes </li></ul></ul><ul><ul><li>probed with radioactive DNA </li></ul></ul><ul><li>Northern Blot </li></ul><ul><ul><li>RNA </li></ul></ul><ul><ul><li>probed with radioactive DNA or RNA. </li></ul></ul><ul><li>Western Blot </li></ul><ul><ul><li>Protein </li></ul></ul><ul><ul><li>probed with radioactive or enzymatically-tagged antibodies. </li></ul></ul>
  12. 15. Complimentarity and Hybridization <ul><li>Complementarity is the sequence-specific or shape-specific molecular recognition that occurs when two molecules bind together. </li></ul><ul><ul><li>The two strands of a DNA double-helix bind because they have complimentary sequences </li></ul></ul><ul><ul><li>An antibody binds to a region of a protein molecule (antigen) because they have complimentary shapes . </li></ul></ul><ul><li>Complementarity between a probe molecule and a target molecule can result in the formation of a probe-target complex. </li></ul>
  13. 16. The Probe-Target Complex <ul><li>The probe-target complex can then be located if the probe molecules are tagged with radioactivity or an enzyme. </li></ul><ul><li>The location of the complex can be used to get information about the target molecule. </li></ul><ul><li>The probe target complex, formed from two types of molecules, is called a hybrid </li></ul><ul><li>In solution, several types of hybrid molecular complexes (hybrids) can exist </li></ul>
  14. 17. Hybrid Types <ul><li>DNA-DNA </li></ul><ul><ul><li>A single-stranded DNA (ssDNA) probe can form a double-stranded, base-paired hybrid with a ssDNA target if the probe sequence is complimentary to the target sequence. </li></ul></ul><ul><li>DNA-RNA. </li></ul><ul><ul><li>A single-stranded DNA (ssDNA) probe can form a double-stranded, base-paired hybrid with an RNA target if the probe sequence is complimentary to the target sequence. </li></ul></ul><ul><li>Protein-Protein. </li></ul><ul><ul><li>An antibody (Ab) probe can form a complex with a target protein if the antibody's antigen-binding site can bind to an epitope (small antigenic region) on the target protein. </li></ul></ul><ul><ul><li>This type of hybrid is called an 'antigen-antibody complex' or 'complex' for short. </li></ul></ul>
  15. 18. Features of Hybridization <ul><li>Hybridization reactions are specific </li></ul><ul><ul><li>probes will only bind to targets with complimentary sequence (or, in the case of antibodies, sites with the correct 3-d shape). </li></ul></ul><ul><li>Hybridization reactions will occur in the presence of large quantities of molecules similar but not identical to the target. </li></ul><ul><ul><li>A probe can find one molecule of target in a mixture of zillions of related but non-complementary molecules. </li></ul></ul><ul><li>These properties allow use hybridization to perform a molecular search for one DNA molecule, or one RNA molecule, or one protein molecule in a complex mixture containing many similar molecules. </li></ul>
  16. 19. The Importance of Hybridization <ul><li>Hybridization techniques allow you to pick out the molecule of interest from the complex mixture of cellular components and study it on its own. </li></ul><ul><li>These techniques are necessary because a cell contains tens of thousands of genes, thousands of different mRNA species, and thousands of different proteins. </li></ul><ul><li>When the cell is broken open to extract DNA, RNA, or protein, the result is a complex mixture of all the cell's DNA, RNA, or protein. </li></ul>
  17. 20. Locating the Target <ul><li>If you mix a solution of DNA with a solution of radioactive probe, you end up with a radioactive solution. </li></ul><ul><ul><li>You cannot tell the hybrids from the non-hybridized molecules. </li></ul></ul><ul><li>First you must physically separate the mixture of molecules on the basis of some convenient parameter. </li></ul><ul><li>The molecules must then be immobilized on a solid support, so that they will remain in position during probing and washing. </li></ul><ul><li>The probe is then added, the non-specifically bound probe is removed, and the probe is detected. </li></ul><ul><li>The place where the probe is detected corresponds to the location of the immobilized target molecule. </li></ul>
  18. 21. Steps in the Process <ul><li>The process has the following steps: </li></ul><ul><li>Gel electrophoresis </li></ul><ul><li>Transfer to solid support </li></ul><ul><li>Blocking </li></ul><ul><li>Preparing the probe </li></ul><ul><li>Hybridization </li></ul><ul><li>Washing </li></ul><ul><li>Detection of probe-target hybrids </li></ul>
  19. 22. Separation by Molecular Weight <ul><li>In Southern, Northern, and Western blots, the initial separation of molecules is on the basis of molecular weight. </li></ul><ul><li>Cloning uses a different technique </li></ul><ul><li>Gel electrophoresis is the usual procedure used </li></ul><ul><li>This separates molecules on the basis of their size. </li></ul>
  20. 23. Gel Electrophoresis <ul><li>First, a slab of gel material is cast. </li></ul><ul><ul><li>Gels are usually cast from agarose or poly-acrylamide. </li></ul></ul><ul><ul><li>Gels are solid and consist of a matrix of long thin molecules forming sub-microscopic pores. </li></ul></ul><ul><ul><li>The size of the pores can be controlled by varying the chemical composition of the gel. </li></ul></ul><ul><li>The gel is placed in a tank holding buffer and equipped with electrodes to apply an electric field </li></ul><ul><li>The properties of the buffer & pH are set so that the molecules being separated carry a net (-) charge </li></ul><ul><li>The charged molecules are moved by the electric field from left to right. </li></ul>
  21. 24. Gel Electrophoresis
  22. 25. Separation of Molecules on a Gel <ul><li>As they move through the gel, larger molecules will be restricted the pores of the gel, while the smaller molecules will move more easily and thus faster. </li></ul><ul><li>This results in a separation by size, with the larger molecules nearer the well and the smaller molecules farther away. </li></ul><ul><li>This separates on the basis of size, not necessarily molecular weight. </li></ul>
  23. 26. Size vs. Molecular Weight <ul><li>Example: two 1000 nucleotide RNA molecules, one a fully extended long chain ( A ); the other can base-pair with itself to form a hairpin structure ( B ): </li></ul><ul><li>As they migrate through the gel, both molecules behave as though they were solid spheres whose diameter is the same as the length of the rod-like molecule. </li></ul><ul><li>Both have the same molecular weight </li></ul><ul><li>B has secondary structure making it smaller than A </li></ul><ul><li>B will migrate faster than A in a gel </li></ul>
  24. 27. Controlling for Shape <ul><li>To prevent differences in shape from confusing measurements of molecular weight, the molecules to be separated must be in a long extend rod conformation </li></ul><ul><li>Different techniques are used to remove secondary or tertiary structure, in preparing DNA, RNA and protein samples for electrophoresis. </li></ul>
  25. 28. Preparation Techniques <ul><li>Preparing DNA for Southern Blots </li></ul><ul><ul><li>DNA is first cut with restriction enzymes </li></ul></ul><ul><ul><li>The resulting double-stranded DNA fragments have an extended rod conformation without pre-treatment. </li></ul></ul><ul><li>Preparing RNA for Northern Blots </li></ul><ul><ul><li>Although RNA is single-stranded, RNA molecules often have small regions that can form base-paired secondary structures. </li></ul></ul><ul><ul><li>RNA is pre-treated with formaldehyde. </li></ul></ul><ul><li>Preparing Proteins for Western Blots </li></ul><ul><ul><li>Proteins have extensive 2' and 3' structures and are not always negatively charged. </li></ul></ul><ul><ul><li>Proteins are treated with detergent (SDS) which removes 2' and 3' structure and coats the protein with negative charges . </li></ul></ul>
  26. 29. Determining Molecular Weight <ul><li>Molecules will be separated by molecular weight </li></ul><ul><li>The distance migrated is ~proportional to the log of the inverse of the molecular weight (the log of 1/MW). </li></ul><ul><li>Molecular weights are measured in different units for DNA, RNA, and protein: </li></ul><ul><li>DNA </li></ul><ul><ul><li>Molecular weight is measured in base-pairs (bp) and commonly in kilobase-pairs (1000bp), or kbp. </li></ul></ul><ul><li>RNA </li></ul><ul><ul><li>Molecular weight is measured in nucleotides (nt) and commonly in kilonucleotides (1000nt), or knt. </li></ul></ul><ul><li>Protein </li></ul><ul><ul><li>Molecular weight is measured in Daltons (grams per mole)(Da), and commonly in kiloDaltons (1000Da), or kDa. </li></ul></ul>
  27. 30. Use of Standards <ul><li>On most gels, one well is loaded with a mixture of DNA, RNA, or protein molecules of known molecular weight. </li></ul><ul><li>These 'molecular weight standards' are used to calibrate the gel run </li></ul><ul><li>The molecular weight of any sample molecule can be determined by interpolating between the standards. </li></ul>
  28. 31. Staining <ul><li>Different stains and staining procedures are used for different classes of macromolecules: </li></ul><ul><li>DNA & RNA </li></ul><ul><ul><li>DNA and RNA are stained with ethidium bromide (EtBr), which binds to nucleic acids. </li></ul></ul><ul><ul><li>The nucleic acid-EtBr complex fluoresces under UV light. </li></ul></ul><ul><li>Protein </li></ul><ul><ul><li>Protein is stained with Coomassie Blue (CB). </li></ul></ul><ul><ul><li>The protein-CB complex is deep blue and can be seen with visible light. </li></ul></ul>
  29. 32. Transfer to Solid Support <ul><li>After the DNA, RNA, or protein has been separated by molecular weight, it must be transferred to a solid support before hybridization. </li></ul><ul><ul><li>Hybridization does not work well in a gel. </li></ul></ul><ul><li>The transfer process is called blotting </li></ul><ul><ul><li>These hybridization techniques are called blots. </li></ul></ul><ul><li>The solid support is often a sheet of nitrocellulose paper (a type of filter paper) </li></ul><ul><ul><li>DNA, RNA, and protein stick well to nitrocellulose in a sequence-independent manner. </li></ul></ul><ul><li>The DNA, RNA, or protein can be transferred to nitrocellulose in one of two ways: </li></ul><ul><ul><li>Electrophoresis </li></ul></ul><ul><ul><li>Capillary blotting </li></ul></ul>
  30. 33. Transfer via Electrophoresis Electrophoresis takes advantage of the molecules' negative charge .
  31. 34. Capillary Blotting The molecules are transferred in a flow of buffer from wet filter paper to dry filter paper.
  32. 35. Blocking <ul><li>The surface of the filter now has the separated molecules on it, as well as many spaces where no molecules have yet bound. </li></ul><ul><li>If we added the probe directly to the filter, the probe would stick to the blank parts of the filter, like the molecules transferred from the gel did. </li></ul><ul><li>During hybridization, we want the probe to bind only to the target molecule. </li></ul><ul><li>To achieve this, the filters are soaked in a blocking solution which contains a high concentration of DNA, RNA, or protein. </li></ul><ul><li>This coats the filter and prevents the probe from sticking to the filter itself. </li></ul>
  33. 36. Preparing the Probe <ul><li>Radioactive DNA probes for Southerns and Northerns </li></ul><ul><ul><li>A radioactive copy of a double-stranded DNA fragment. </li></ul></ul><ul><ul><li>Begins with a restriction fragment of a plasmid containing the gene of interest. </li></ul></ul><ul><ul><li>The DNA restriction fragment (template) is radiolabeled </li></ul></ul><ul><ul><li>This produces a radioactive single-stranded DNA copy of both strands of the template for use as a probe. </li></ul></ul>
  34. 37. Probes for Westerns <ul><li>Radioactive Antibodies for Westerns </li></ul><ul><ul><li>Antibodies are raised by injecting a purified protein into an animal, usually a rabbit or a mouse. </li></ul></ul><ul><ul><li>This produces an immune response to that protein. </li></ul></ul><ul><ul><li>Antibodies isolated from the serum (blood) of that rabbit will bind to the protein used for immunization. </li></ul></ul><ul><ul><li>Antibodies are protein molecules </li></ul></ul><ul><ul><li>They are labeled by chemically with iodine-125 which is radioactive. </li></ul></ul><ul><li>Enzyme-conjugated Antibodies for Westerns </li></ul><ul><ul><li>Antibodies against a particular protein are raised as above </li></ul></ul><ul><ul><li>These are labeled by chemically cross-linking the antibody molecules to molecules of an enzyme. </li></ul></ul><ul><ul><li>The resulting antibody-enzyme conjugate is still able to bind to the target protein. </li></ul></ul>
  35. 38. Hybridization & Washing <ul><li>In all three blots, the labeled probe is added to the blocked filter paper in buffer to allow hybridization </li></ul><ul><li>This is incubated for several hours to allow the probe molecules to find their targets. </li></ul><ul><li>After hybrids have formed it is necessary to remove any probe that is on the filter but not stuck to the target molecules. </li></ul><ul><li>To do this, the filter is rinsed repeatedly in several changes of buffer to wash off any un-hybridized probe. </li></ul>
  36. 39. Detecting the Probe-Target Hybrids <ul><li>The nitrocellulose looks like blank paper </li></ul><ul><ul><li>You must now detect where the probe has bound. </li></ul></ul><ul><li>Autoradiography </li></ul><ul><ul><li>If the probe is radioactive, it can expose X-ray film. </li></ul></ul><ul><ul><li>X-ray film is pressed against the filter </li></ul></ul><ul><ul><li>After development, there will be dark spots on the film wherever the probe bound. </li></ul></ul><ul><li>Enzymatic Development </li></ul><ul><ul><li>If an antibody-enzyme conjugate was used as a probe, this can be detected by soaking the filter in a solution of a substrate for the enzyme. </li></ul></ul><ul><ul><li>The substrates used produce colored product when acted on by the enzyme. </li></ul></ul><ul><ul><li>This produces a colored deposit wherever the probe bound . </li></ul></ul>
  37. 40. Southern Blot
  38. 41. Cloning a Gene by Hybridization : <ul><li>We want to end up with a plasmid which contains a fragment of human DNA which includes the gene of interest </li></ul><ul><li>We can not isolate the human gene DNA from either the gel or the filter </li></ul><ul><ul><li>At each molecular weight on the gel, there are many bands of the same length but different sequences. </li></ul></ul><ul><ul><li>Therefore, separating the DNA fragments by molecular weight is unsuitable. </li></ul></ul><ul><li>Instead, we separate them by sequence </li></ul>
  39. 42. Constructing a Genomic Library <ul><li>We create a collection of plasmids, physically separated, each containing a different fragment of human DNA. </li></ul><ul><li>This is a plasmid library of human DNA restriction fragments. </li></ul><ul><li>The plasmids are transferred to bacteria </li></ul><ul><li>This results in a collection of bacterial colonies, each containing a different plasmid with a different inserted piece of human DNA </li></ul><ul><li>These bacteria are grown on agar plates </li></ul><ul><li>Previously described searching techniques can then be used to isolate the gene of interest </li></ul>
  40. 43. Genomic Libraries
  41. 44. Plasmid Biotechnology
  42. 45. Polymerase Chain Reaction <ul><li>The polymerase chain reaction (PCR) is widely used in research laboratories and doctor's offices </li></ul><ul><li>This techniques “xeroxes” DNA </li></ul><ul><li>PCR mimics the process of DNA replication in a test tube. </li></ul><ul><li>PCR relies on the ability of DNA-copying enzymes to remain stable at high temperatures. </li></ul><ul><li>PCR uses polymerase derived from Thermus aquaticus, a bacterium found in hot springs in Yellowstone Park </li></ul><ul><ul><li>Extremely heat tolerant </li></ul></ul>
  43. 46. Polymerase Action <ul><li>When a cell divides, polymerase enzymes make a copy of the DNA in each chromosome. </li></ul><ul><li>The first step in this process is to &quot;unzip&quot; the two DNA chains of the double helix. </li></ul><ul><li>As the two strands separate, DNA polymerase makes a copy using each strand as a template. </li></ul>
  44. 47. Elements of a PCR <ul><li>PCR entails 3 steps: </li></ul><ul><ul><li>Separation of the strands </li></ul></ul><ul><ul><li>Annealing the primer to the template </li></ul></ul><ul><ul><li>Synthesis of new strands </li></ul></ul><ul><li>All three steps are carried out in the same vial. </li></ul><ul><li>The entire process takes less than two minutes. </li></ul><ul><li>A PCR vial contains all the necessary components for DNA duplication: </li></ul><ul><ul><li>A piece of DNA </li></ul></ul><ul><ul><li>Large quantities of the four nucleotide </li></ul></ul><ul><ul><li>Large quantities of the primer sequence </li></ul></ul><ul><ul><li>DNA polymerase. </li></ul></ul>
  45. 48. Temperature Dependent Steps <ul><li>The 3 parts of the PCR are carried out in the same vial, but at different temperatures. </li></ul><ul><li>The first part of the process separates the two DNA chains in the double helix. </li></ul><ul><ul><li>This is done by heating the vial to 90-95 o Cfor 30 seconds. </li></ul></ul><ul><li>Primers cannot bind DNA strands this high temperature </li></ul><ul><ul><li>The vial is cooled to 55 o C </li></ul></ul><ul><ul><li>At this temperature, the primers bind or &quot;anneal&quot; to the ends of the DNA strands. </li></ul></ul><ul><li>The final step is to make a complete copy of the templates. </li></ul><ul><ul><li>The Taq polymerase works best at ~75 o C </li></ul></ul><ul><ul><li>The temperature of the vial is raised. </li></ul></ul>
  46. 49. The PCR Process <ul><li>Taq polymerase begins adding nucleotides to the primer </li></ul><ul><li>This continues until a complete, complimentary strand is produced </li></ul><ul><li>At the end of a cycle, each piece of DNA in the vial has been duplicated. </li></ul><ul><li>Each newly synthesized DNA piece can act as a new template </li></ul><ul><ul><li>The cycle can be repeated 30 or more times. </li></ul></ul><ul><ul><li>After 30 cycles, 1 million copies of a single piece of DNA can be produced! </li></ul></ul><ul><ul><li>1 million copies can be ready in about three hours. </li></ul></ul><ul><li>Small samples of DNA can produce sufficient copies to carry out forensic tests. </li></ul>
  47. 50. A Polymerase Chain Reaction
  48. 51. DNA Fingerprinting <ul><li>Each person has a unique DNA fingerprint. </li></ul><ul><li>A DNA fingerprint is the same for every cell, tissue, and organ of a person. </li></ul><ul><li>It cannot be altered by any known treatment. </li></ul><ul><li>DNA fingerprinting is a quick way to compare the DNA sequences of any two living organisms. </li></ul><ul><li>DNA fingerprinting has become the primary method for identifying and distinguishing among individual human beings. </li></ul><ul><li>An additional application of DNA fingerprint technology is the diagnosis of inherited disorders </li></ul>
  49. 52. RFLP Allele Analysis
  50. 53. Steps in DNA Fingerprinting <ul><li>1. Isolation of DNA </li></ul><ul><ul><li>DNA is recovered from cells or tissues of the body. </li></ul></ul><ul><ul><li>Only a small amount of tissue is needed. </li></ul></ul><ul><ul><li>The amount of DNA found at the root of one hair is usually sufficient. </li></ul></ul><ul><li>2. Cutting, sizing, and sorting </li></ul><ul><ul><li>Restriction enzymes are used to cut the DNA at specific places. </li></ul></ul><ul><ul><li>The DNA pieces are sorted according to size by gel electrophoresis. </li></ul></ul>
  51. 54. Steps in DNA Fingerprinting, Cont . <ul><li>3. Transfer of DNA to nylon </li></ul><ul><ul><li>The distribution of DNA pieces is transferred to a nylon sheet by placing the sheet on the gel and soaking them overnight. </li></ul></ul><ul><li>4-5. Probing </li></ul><ul><ul><li>Adding radioactive or colored probes to the nylon sheet produces a pattern called a DNA fingerprint. </li></ul></ul><ul><ul><li>Each probe typically sticks in only one or two specific places on the nylon sheet. </li></ul></ul><ul><li>6. DNA fingerprint </li></ul><ul><ul><li>The final DNA fingerprint is built by using several probes (5-10 or more) simultaneously. </li></ul></ul><ul><ul><li>It resembles the bar codes used by grocery store scanners </li></ul></ul>
  52. 55. Uses of DNA Fingerprints <ul><li>DNA fingerprints are useful in several applications of human health care research, as well as in the justice system. </li></ul><ul><ul><li>Used to establish paternity </li></ul></ul><ul><ul><li>Used to identify criminal suspects </li></ul></ul><ul><ul><li>Used as a diagnostic tool for inherited disorders </li></ul></ul>
  53. 57. Diagnosis of Inherited Disorders <ul><li>DNA fingerprinting is used to diagnose inherited disorders in both prenatal and newborn babies </li></ul><ul><ul><li>These disorders may include cystic fibrosis, hemophilia, Huntington's disease, familial Alzheimer's, sickle cell anemia, thalassemia, and many others. </li></ul></ul><ul><li>Early detection enables the medical staff to prepare themselves and the parents for proper treatment of the child. </li></ul><ul><li>Genetic counselors can use DNA fingerprint information to help prospective parents understand the risk of having an affected child. </li></ul><ul><ul><li>Prospective parents may use DNA fingerprint information in their decisions concerning affected pregnancies. </li></ul></ul>
  54. 58. <ul><li>Even if the precise locus of a disease causing allele is unknown, its presence can be often be detected </li></ul><ul><li>Test for RFLP markers that are close to the gene of interest </li></ul><ul><li>Basis of sometimes family-specific genetic testing </li></ul>
  55. 59. Developing Cures for Inherited Disorders <ul><li>Research to locate inherited disorders on specific chromosomes depends on the information contained in DNA fingerprints. </li></ul><ul><li>By studying the DNA fingerprints of relatives who have a history of a particular disorder, or by comparing large groups of people with and without the disorder, it is possible to identify DNA patterns associated with the disease </li></ul><ul><li>This work is a necessary first step in designing an eventual genetic cure for these disorders . </li></ul>
  56. 60. Personal Identification <ul><li>Every organ or tissue of an individual contains the same DNA fingerprint </li></ul><ul><li>The U.S. armed services has begun a program to collect DNA fingerprints from all personnel for use later, in case they are needed to identify casualties or persons missing in action. </li></ul><ul><li>The DNA method will be far superior to the dogtags, dental records, and blood typing strategies currently in use.   </li></ul>