Downloaded 960 times
Uploaded byGovernment Medical College
Stem cell and its clinical implication
This document discusses stem cells and their clinical implications. It begins by defining stem cells and outlining their ability to self-renew and differentiate. The document then reviews the history of stem cell research, types of stem cells based on potential, sources of stem cells, the steps of stem cell therapy, and potential applications of stem cells. It also debates the arguments for and against stem cell research.
More Related Content
Similar to Stem cell and its clinical implication
More from Government Medical College
Stem cell and its clinical implication
- 1. Stem Cell andIts Clinical Implications
- 2. Presented by: DR.Mahfujun Nahar MSPhase-A Resident Department of Anatomy BSMMU
- 3. Guided by Dr. NahidFarhana Amin Assistant Professor Department of Anatomy BSMMU
- 4. Objectives • Define stemcell • Outline brief history of stem cell research • Mention the types of stem cells based on potential
- 5. Objectives (contd) • Outlinethe sources of stem cell • Explain the steps of stem cell therapy • Discuss the health problems that might be treated by stem cells
- 6. Objectives (Contd) • Debatefor and against stem cell research • Mention the responsibilities regarding stem cell issues
- 7. Stem Cells: Definition -unspecialized - self renewal - can be induced to form specific cell types
- 8. 1 stem cell Selfrenewal - maintains the stem cell pool 4 specialized cells Differentiation replaces dead or damaged cells throught the life Why self-renew AND differentiate? 1 stem cell
- 9. Clonogenic, a singleES cell gives rise to a colony of genetically identical cells, which have the same properties as the original cell Expresses the transcription factor Oct-4 Can be induced to continue proliferating or to differentiate Lacks the G1 checkpoint in the cell cycle ES cells spend most of their life cycle in S phase Don’t show X inactivation Properties of stem cell….
- 10. Stem Cell Markers c-Kit Oct4(ATGCAAAT) POU Family Protein CD34 CD38 Cd44 CD133 Nestin
- 11. Cells in suspensionare tagged with fluorescent markers specific for undifferentiated stem cell Labeled cells are sent under pressure through a small nozzle and pass through an electric field A cell generates a negative charge if it fluoresces and a positive charge if it does not. Laser beam passes through one cell FLUROSCENT ACTIVATED CELL SORTING Stem cell SEPARATION OF STEM CELL
- 12. History of Stem CellResearch
- 13. • In 1998,James Thomson isolated stem cells from the inner cell mass of the early embryo. • In 1998, John Gearhart derived human embryonic germ cells from fetal gonadal tissue (primordial germ cells). History of Stem Cell Research
- 14. History of StemCell Research (Contd) 1999 - First Successful human transplant of insulin-making cells from cadavers 2001 - President Bush restricted federal funding for embryonic stem-cell research
- 15. History of StemCell Research (Contd) 2004 - Harvard researchers grow stem cells from embryos using private funding. Asia, Japan, South Korea and Singapore is moving forwards on stem cell research.
- 16. SCAN – StemCell Action Network Stem Cell Research Worldwide
- 17. Global status • Ongoingdebate regarding use of embryos • United Nations: proposal for a global policy to ban reproductive cloning only
- 18. Debate in US •Federal funding available for research using the Bush lines only ES cell lines from 8/9/01 • Disadvantage of Bush stem cell lines: may have mutations or infections • Private companies continue to pursue stem cell research therapeutic cloniing mainly
- 19. Stem cell researchin other countries • Great Britain –Therapeutic cloning , use of excess embryos & creation of embryos allowed • France –Reproductive and therapeutic cloning banned • Germany –Use of excess embryos and creation of embryos banned
- 20. Types of StemCellsTypes of Stem Cells based on potentialbased on potential
- 21. Types of StemCells based on potential Stem cellStem cell typetype DescriptionDescription ExamplesExamples TotipotentTotipotent Each cell can developEach cell can develop into a new individualinto a new individual Cells from earlyCells from early (1-3 days)(1-3 days) embryosembryos PluripotentPluripotent Cells can form anyCells can form any (over 200) cell types(over 200) cell types Some cells ofSome cells of blastocyst (5 toblastocyst (5 to 14 days)14 days) MultipotentMultipotent Cells differentiated,Cells differentiated, but can form a numberbut can form a number of other tissuesof other tissues Fetal tissue, cordFetal tissue, cord blood, and adultblood, and adult stem cellsstem cells
- 22. This cell Can formthe Embryo and placenta This cell Can just form the embryo Fully mature
- 23. Pluripotent Stem Cells morepotential to become any type of cell
- 24. Multipotent stem cells •Multipotent stem cells – limited in what the cells can become
- 25. Sources of StemCell
- 26. Sources of StemCell • Embryonic stem (ES) cells • Tissue (Adult) stem cells • Induced pluripotent stem cells (iPS cells) • Somatic cell nuclear transfer (therapeutic cloning)
- 27. Sources of stemcells embryonic stem cells blastocyst - a very early embryo tissue stem cells fetus, baby and throughout life
- 28. Embryonic stem (ES)cells: blastocyst outer layer of cells = ‘trophectoderm’ cells inside = ‘inner cell mass’ embryonic stem cells taken from the inner cell mass culture in the lab to grow more cells fluid with nutrients
- 29. Embryonic stem (ES)cells: embryonic stem cells PLURIPOTENT all possible types of specialized cells differentiation
- 30. Tissue stem cells: muscles skin surfaceof the eye brain breast intestines (gut) bone marrow testicles
- 31. Tissue stem cells: MULTIPOTENT bloodstem cell found in bone marrow differentiation only specialized types of blood cell: red blood cells, white blood cells, platelets
- 32. Induced pluripotent stemcell cell from the body ‘genetic reprogramming’ = add certain genes to the cell induced pluripotent stem (iPS) cell behaves like an embryonic stem cell Advantage: no need for embryos! all possible types of specialized cells culture iPS cells in the lab differentiation
- 33. Induced pluripotent stemcell (Contd) cell from the body (skin) genetic reprogramming pluripotent stem cell differentiation
- 34. Somatic cell nucleartransfer • A nucleus from an adult donor cell is inserted into a recipient egg cell from which the nucleus has been removed • The resulting cell is then stimulated to divide as a zygote later forming embryo genetically identical to the adult donor cell
- 35. Somatic cell nucleartransfer
- 36. Goals of therapeuticcloning –Use embryo as source for ES cells –Use ES cells to generate an organ with genetic markers identical to the patient –Correct genetic error in ESC in blastula stage
- 38. Pitfalls of therapeuticcloning • Large number of eggs needed for SCNT • To harvest large number of eggs: –excessive hormone treatment may induce high rate of ovulation –will carry species-specific mitochondrial genes • Mixing species is reason for concern!
- 39. Cloning There are twoVERY different types of cloning: Reproductive cloning Used to make two identical individuals Very difficult to do Illegal to do on humans Molecular cloning Used to study what a gene does Routinely used in the biology labs gene 1 gene 2
- 40. Reproductive cloning remove nucleus andtake the rest of the cell egg take the nucleus (containing DNA) cell from the body Clone identical to the individual that gave the nucleus Dolly the sheep
- 41. Molecular cloning gene 1 gene2 2) Make a new piece of DNA gene 1 gene 2 1) Take DNA out of the nucleus cell 1 cell 2 gene 1 gene 2 3) Put new DNA into a test cell and grow copies gene 1 cell divides Daughter cells contain same DNA: Genes 1 and 2 have been cloned gene 2 insert new DNA
- 42. Steps of StemCell Therapy
- 43. Steps of StemCell Therapy • Defining the problem • Finding The Right Type of Stem Cell • Match The Stem Cell With The Recipient • Put the stem cells in the right place • Make The Transplanted Stem Cells Perform
- 44. Steps of StemCell Therapy • Define the problem Researchers want to replace dead dopamine neurons with healthy ones
- 45. • Finding TheRight Type of Stem Cell Blastocyst stem cells? At the time, unable to differentiate into neurons Fetal stem cells?, Excellent candidates, ethical problems Adult stem cells?, Hard to get, too little known Steps of Stem Cell Therapy
- 46. • Match TheStem Cell With The Recipient Needs a good immunonlogical match. Steps of Stem Cell Therapy (contd.)
- 47. • Put thestem cells in the right place Surgical procedure usually required. Small holes drilled in the skull, cells injected with a needle. Steps of Stem Cell Therapy (contd.)
- 48. • Make TheTransplanted Stem Cells Perform There was no guarantee how the transplanted cells would behave. If they did not respond to the proper signals from their environment, they might have malfunctioned or died. Steps of Stem Cell Therapy (contd.)
- 49. Cell Culture Techniquesfor ESC • Isolate & transfer of inner cell mass into plastic culture dish that contains culture medium • Cells divide and spread • Inner surface of culture dish is typically coated with mouse embryonic skin cells that have been treated so they will not divide
- 50. • This coatingis called feeder layer: – provide ES cells with a sticky surface for attachment and release nutrients –There are methods for growing embryonic stem cells without mouse feeder cells • ES cells are removed gently and plated into several different culture plates
- 51. Debate for and againststem cell research
- 54. Pro-choice people • “Utilitarianism- destruction of smaller group for the sake of a larger group is justifiable.” • …lead to significant information about the cause, new treatment possibilities, and potential cure for many diseases.
- 55.
- 56. Opinions against stemcell research Stem cells are taken from a human blastocyst, which is then destroyed. This amounts to “murder.” There is a risk of commercial exploitation of the human participants in ESCR.
- 58. Stem cell workmay bypass objections
- 59. Stem-cell work maybypass objections
- 60.
- 61. Potential Uses ofStem Cells • Basic research – clarification of complex events such as –Molecular mechanisms for gene control –Role of signals in gene expression & differentiation of the stem cell –Stem cell theory of cancer
- 62. Potential uses cont. •Biotechnology(drug discovery & development –Safety testing of new drugs on differentiated cell lines –Screening of potential drugs
- 63. Potential uses cont. •Cell based therapies: –Regenerative therapy to treat Parkinson’s, heart disease, diabetes etc –Stem cells in gene therapy as vehicles –Stem cells in therapeutic cloning
- 64. Stem Cell ApplicationsStemCell Applications • Tissue repair - nerve, heart, muscle, organ, skin • Cancers • Autoimmune diseases - diabetes, rheumatoid arthritis, multiple sclerosis.
- 66. Tissue Repair • Regeneratespinal cord, heart tissue or any other major tissue in the body.
- 67.
- 68. Heart Disease • Adultbone marrow stem cells injected into the hearts are believed to improve cardiac function in victims of heart failure or heart attack
- 70. Leukemia and Cancer •Leukemia patients treated with stem cells emerge free of disease. • Stem cells have also reduces pancreatic cancers in some patients. Proliferation of white cells
- 71. Rheumatoid Arthritis • AdultStem Cells may be helpful in jumpstarting repair of eroded cartilage.
- 72. Type I Diabetes •Embryonic Stems Cells might be trained to become pancreatic islets cells needed to secrete insulin.
- 73. • window toearly brain development • Identify critical genes Down Syndrome
- 74. Diseases that aretreated by stem cells are: 1) Acute Leukemia • Acute Lymphoblast Leukemia (ALL) • Acute Myelogenous Leukemia (AML) • Acute Biphenotypic Leukemia • Acute Undifferentiated Leukemia 2) Chronic Leukemia • Chronic Myelogenous Leukemia (CML) • Chronic Lymphocytic Leukemia (CLL) • Juvenile Chronic Myelogenous Leukemia (JCML) • Juvenile Myelomonocytic Leukemia (JMML) Syndromes • Myelodysplastic Syndromes • Amyloidosis • Chronic Myelomonocytic Leukemia (CMML) • Refractory Anemia (RA) • Refractory Anemia with Excess Blasts (RAEB) • Refractory Anemia with Excess Blasts in Transformation • (RAEB-T) • Refractory Anemia with Ringed Sideroblasts (RARS)
- 75. Disorders 1) Stem CellDisorders • Aplastic Anemia (Severe) • Fanconi Anemia • Paroxysmal Nocturnal Hemoglobinuria • Congenital Cytopenia • Dyskeratosis Congenita 2) Myeloproliferative Disorders • Acute Myelofibrosis • Agnogenic Myeloid Metaplasia • Polycythemia Vera • Essential Thrombocythemia 3) Lymphoproliferative Disorders • Non-Hodgkin’s Lymphoma • Hodgkin’s disease • Prolymphocytic Leukemia 4) Phagocyte Disorders • Chediak-Higashi Syndrome • Chronic Granulomatous Disease • Neutrophil Actin Deficiency • Reticular Dysgenesis 5) Inherited Metabolic Disorders • Mucopolysaccharidoses (MPS) • Hurler’s Syndrome (MPS-IH) • Scheie Syndrome (MPS-IS) • Hunter’s Syndrome (MPS-II) • Sanfilippo Syndrome (MPS-III) • Morquio Syndrome (MPS-IV) • Maroteaux-Lamy Syndrome (MPS-VI) • Sly Syndrome, Beta-Glucuronidase Deficiency • Adrenoleukodystrophy • Mucolipidosis II (I-cell Disease) • Krabbe Disease • Gaucher’s Disease • Niemann-Pick Disease • Wolman Disease • Metachromatic Leukodystrophy 6) Histiocytic Disorders • Familial Erythrophagocytic Lymphohistiocytosis • Histiocytosis-X • Hemophagocytosis • Langerhans’ Cell Histiocytosis
- 76. 7) Inherited ImmuneSystem Disorders • Ataxia-Telangiectasia • Kostmann Syndrome • Leukocyte Adhesion Deficiency • DiGeorge Syndrome • Bare Lymphocyte Syndrome • Omenn’s Syndrome • Severe Combined Immunodeficiency • SCID with Adenosine Deaminase Deficiency • Absence of T & B Cells SCID • Absence of T Cells, Normal B Cell SCID • Common Variable Immunodeficiency • Wiskott-Aldrich Syndrome • X-Linked Lymphoproliferative Disorder Other Inherited Disorders • Lesch-Nyhan Syndrome • Cartilage-Hair Hypoplasia • Glanzmann Thrombasthenia • Osteopetrosis • Adrenoleukodystrophy • Ceroid Lipofuscinosis • Congenital Erythropoietic Porphyria • Sandhoff Disease 9) Plasma Cell Disorders • Multiple Myeloma • Plasma Cell Leukemia • Waldenstrom’s Macroglobulinemia • Amyloidosis Abnormalities 1) Inherited Platelet Abnormalities Congenital Thrombocytopenia 2) Inherited Erythrocyte Abnormalities • Beta Thalassemia Major • Sickle Cell Disease • Blackfan-Diamond Anemia • Pure Red Cell Aplasia Other Malignancies • Ewing Sarcoma • Neuroblastoma • Renal Cell Carcinoma • Retinoblastoma • Brain tumor • Ovarian Cancer • Small Cell Lung Cancer • Testicular Cancer
- 77.
- 78. Responsibilities regarding stemcell issues Become informed The facts about stem cell research and its curative potential. www.stemcellfunding.org www.stemcellaction.org
- 79. Responsibilities regarding stem cellissues(contd.) Inform others • Contact patient and community groups and offer to give a presentation like this one. Organize a house party to help spread the word. • Collect email addresses of supporters to be added to mailing list.
- 80. Responsibilities regarding stem cellissues (contd.) Inform others • Arrange to meet with your political representatives to discuss their support for stem cell research • Find other like-minded people and work together • Invite friends, colleagues, and caretakers of patients to become involved
- 81. Technical Challenges • Source- Cell lines may have mutations • Delivery to target areas • Prevention of rejection • Suppressing tumors
- 82. Mutations can leadto leukemia Problems with Adult Stem Cells
- 83. REFERENCES • Stem cellsin class; Badran, Shahira; Bunker Hill Community College, 2007, Boston Museum of Science Biotechnology Symposium • Stem cells & Cloning Stem cells & Cloning; David A. Prentice, Benjamin Cummings, 2003 • http://stemcells.nih.gov/info/scireport/2001report.htm • http://www.ulb.ac.be/sciences/biodic/biodic/images/bio_animale/em bryologie/fecondation/baefec_01_01.jpg • http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.3748 • http://www.news.wisc.edu/packages/stemcells/illustration.html • http://www.drugs.com/enc/images/images/en/17010.jpg • http://embryology.med.unsw.edu.au/Notes/placenta.htm • http://www.dnalc.org/stemcells.html • http://gslc.genetics.utah.edu/units/stemcells/
- 84.
Editor's Notes
- #9 Why self-renew AND differentiate? 1) Self renewal is needed because if the stem cells didn’t copy themselves, you would quickly run out. It is important for the body to maintain a pool of stem cells to use throughout your life. 2) Differentiation is important because specialized cells are used up, damaged or die all the time during your life. Specialized cells cannot divide and make copies of themselves, but they need to be replaced for your body to carry on working. For example, your body needs 100,000 million new blood cells every day. Of course, differentiation is also important for making all the different kinds of cell in the body during development of an embryo from a single fertilized egg. Possible questions or misconceptions 1) School students may have learnt simply that ‘cells undergo mitosis to make copies of themselves to heal wounds or replace blood cells’. You may need to explain that specialized cells like skin, red blood or gut cells cannot undergo mitosis, which is why you need stem cells. There are a few exceptions (e.g. liver cells or T-cells) but in general specialized cells can no longer divide. For adult audiences, this could be expanded to cover the idea that there are intermediate cells (progenitors) between stem cells and specialized cells that divide to allow a large number of new cells to be made (see slide 26 on renewing tissues) 2) Scientists think that stem cells in the human body don’t generally divide to produce one stem cell and one specialized cell at the same time. They probably divide to make EITHER two stem cells, OR two more specialized cells. In fruit flies, stem cells can divide to make one stem cell and one more specialized cell.
- #14 Human embryonic stem cells were first isolated in 1998. The cells from these embryos were established as immortal pluripotent cell lines that are still in existence today.
- #22 Stem cells can be classified into three broad categories, based on their ability to differentiate. Totipotent stem cells are found only in early embryos. Each cell can form a complete organism (e.g., identical twins). Pluripotent stem cells exist in the undifferentiated inner cell mass of the blastocyst and can form any of the over 200 different cell types found in the body. Multipotent stem cells are derived from fetal tissue, cord blood and adult stem cells. Although their ability to differentiate is more limited than pluripotent stem cells, they already have a track record of success in cell-based therapies. Here is a current list of the sources of stem cells: Embryonic stem cells - are harvested from the inner cell mass of the blastocyst seven to ten days after fertilization. Fetal stem cells - are taken from the germline tissues that will make up the gonads of aborted fetuses. Umbilical cord stem cells - Umbilical cord blood contains stem cells similar to those found in bone marrow. Placenta derived stem cells - up to ten times as many stem cells can be harvested from a placenta as from cord blood. Adult stem cells - Many adult tissues contain stem cells that can be isolated.
- #23 CLICK! This diagram will eventually show the entire range of development, from fertilized egg to mature cell types in the body. Each cell in the 8-cell embryo, here in red, can generate every cell in the embryo as well as the placenta and extra-embryonic tissues. These cells are called CLICK! TOTIPOTENT stem cells. Why are they called totipotent? (wait for answers) Because one red cell can potentially make all necessary tissues for development. CLICK! During In Vitro Fertilization, can parents choose whether their baby is going to be a boy or a girl? (wait) Yes, there is a widely-practiced procedure called pre-implantation genetic diagnosis, where one cell is removed from the 8-cell embryo and its DNA is examined. What might you look for when trying to identify the embryo’s sex? (wait) If there’s an X and Y chromosome it’s a boy and if there are two X’s it’s a girl. The parents can decide whether to implant it. Also parents with a genetic disease might want to see if their baby has any identifiable genetic disorders and decide whether to implant based on this information. Pre-implantation genetic diagnosis doesn’t destroy the embryo. Scientists are attempting to adapt this pre-implantation genetic diagnosis procedure and use it to create a stem cell line from one single TOTIPOTENT cell, without destroying the embryo. The embryonic stem cells inside the blastocyst, here in purple, can generate every cell in the body except placenta and extra-embryonic tissues. These are called CLICK! PLURIPOTENT stem cells…why? (wait for answers) Because they can differentiate into all the 200+ cell types in the body, but they do not form the placenta. CLICK! Pluripotent stem cells can be isolated and grown in culture, or left to develop into more specialized cells in the body. CLICK! Adult stem cells or tissue-specific stem cells have restricted lineages. Adult stem cells show up when the three distinct layers form in the 14-day-old embryo, and are present in the fetus, baby, child, and so forth. Adult just means they’ve gone further down their lineage pathway than the initial stem cells in the embryo. They are called CLICK! MULTIPOTENT stem cells because they will only become mature cells from the tissue in which they reside. Adult stem cells are present throughout your life and replace fully mature CLICK! , yet damaged and dying cells. So to review (if time): TOTIPOTENT stem cells come from embryos that are less than 3 days old. These cells can make the TOTAL human being because they can form the placenta and all other tissues. PLURIPOTENT stem cells come from embryos that are 5-14 days old. Embryos and fetuses that are older than 14 days DO NOT contain pluripotent cells. These cells can form every cell type in the body but not the placenta. MULTIPOTENT stem cells are also called adult stem cells and these appear in the 14 day old embryo and beyond. At this point these stem cells will continue down certain lineages and CANNOT naturally turn back into pluripotent cells or switch lineages.
- #28 Where are stem cells found? There are different types of stem cells: Embryonic stem cells: found in the blastocyst, a very early stage embryo that has about 50 to 100 cells; Tissue stem cells: found in the tissues of the body (in a fetus, baby, child or adult). (Tissue stem cells are sometimes referred to as adult stem cells, even though they are found in the fetus and in babies, as well as in adults.)
- #29 Embryonic stem cells: Where they come from Embryonic stem (ES) cells are taken from inside the blastocyst, a very early stage embryo. The blastocyst is a ball of about 50-100 cells and it is not yet implanted in the womb. It is made up of an outer layer of cells, a fluid-filled space and a group of cells called the inner cell mass. ES cells are found in the inner cell mass. For a simple, clear explanation of how embryonic stem cells are obtained, watch the film, “A Stem Cell Story”, at www.eurostemcell.org/films
- #30 Embryonic stem cells: What they can do Embryonic stem cells are exciting because they can make all the different types of cell in the body – scientists say these cells are pluripotent.
- #31 Tissue stem cells: Where we find them We all have stem cells in our bodies all the time. They are essential for keeping us fit and healthy. They replace cells that are damaged or used up. Scientists are still learning about all the different kinds of tissue stem cells found in our bodies and how they work.
- #32 Tissue stem cells: What they can do Tissue stem cells can often make several kinds of specialized cell, but they are more limited than embryonic stem cells. Tissue stem cells can ONLY make the kinds of cell found in the tissue they belong to. So, blood stem cells can only make the different kinds of cell found in the blood. Brain stem cells can only make different types of brain cell. Muscle stem cells can only make muscle cells. And so forth. Scientists say that tissue stem cells are multipotent because they can make multiple types of specialized cell, but NOT all the kinds of cell in your body.
- #33 Induced pluripotent stem cells (iPS cells) Note: This slide contains a lot of information and may be too complex for some audiences unless there is plenty of time for explanations and discussions. What are iPS cells? In 2006, scientists discovered that it is possible to make a new kind of stem cell in the laboratory. They found that they could transform skin cells from a mouse into cells that behave just like embryonic stem cells. In 2007, researchers did this with human cells too. The new stem cells that are made in the lab are called induced pluripotent stem cells . Just like embryonic stem cells, they can make all the different types of cell in the body – so we say they are pluripotent . Making induced pluripotent stem (iPS) cells is a bit like turning back time. Scientists add particular genes to cells from the body to make them behave like embryonic stem cells. Genes give cells instructions about how to behave. So, this process is a bit like changing the instructions in a computer programme to make the computer do a new task. Scientists call the process they use to make iPS cells ‘genetic reprogramming’. Why are they exciting? Researchers hope that one day they might be able to use iPS cells to help treat diseases like Parkinson’s or Alzheimer’s. They hope to: Take cells from the body - like skin cells - from a patient Make iPS cells Use those iPS cells to grow the specialized cells the patient needs to recover from the disease, e.g. certain brain cells. These cells would be made from the patient’s own skin cells so the body would not reject them. There is a long way to go before scientists can do this, but iPS cells are an exciting discovery.
- #34 Induced pluripotent stem cells (iPS cells) This is an alternative representation of the same information as on the previous slide. Please see the previous explanatory notes.
- #40 Cloning When most people think of cloning, they think of the idea of making a copy of an individual – an animal or even a person. This is called reproductive cloning . It hit the headlines in the late 1990s when ‘Dolly the sheep’ was cloned. She was the first mammal ever to be cloned. In fact, this kind of cloning is very difficult to do and it is illegal even to try to clone a human being. There is another type of cloning that many biologists do every day: molecular cloning . This is a technique used to help scientists investigate what particular genes do and how they work. The following slides explain these processes in more detail.
- #42 Molecular cloning: Principles Molecular cloning is a process used by scientists to make copies of a particular gene or genes inside a cell. They use the technique to find out more about what certain genes do or how they work. Molecular cloning is done routinely in laboratories today. It involves several steps: Take the DNA out of a cell. Cut out the gene you are interested in (gene 2 in this example). Insert it into a strand of DNA taken from another cell. The gene is not literally cut out with a knife or scissors – carefully chosen enzymes break the DNA chain at particular points. More enzymes are used to insert the gene into another piece of DNA at exactly the right place (in this example, next to gene 1). Once you have made a piece of DNA containing the gene you want to study, put your new DNA into a test cell. When the cell divides, it makes copies of itself. Each new daughter cell contains an exact copy of the DNA in your test cell, including genes 1 and 2. The genes have therefore been copied and we say they have been cloned. This is a simplified description of the technique. There are some intermediate steps involved and the details of the technique can vary, but this scheme illustrates the key principle, i.e. we are able to make cells containing particular genes in order to find out what those genes do. Some examples of how this technique can be used are given on the next slide.