Biotechnology. Biotechnology. Early Biotechnology

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1 Biotechnology Stem cells 1 Biotechnology An inclusive definition of biotechnology is human intervention with life processes to produce effects for human benefit. These interventions go back to the beginnings of civilization. 2 Early Biotechnology Domestication of animals and selective breeding. Selection and preservation of seeds and the deliberate planting of crops. Organisms used in food preparation and preservation: Bacteria to cause fermentation for beer & wines Yeast for bread and beer. 3

2 Crop rotation Though they did not know it, ancient practices of crop rotation improved agricultural yields by releasing organisms that fixed atmospheric nitrogen in the soil. The ancient Greek botanist Theophrastus said that broad beans left magic in the soil. 4 Microorganisms and Cells Progress in biotechnology depended on our understanding of life processes that occur below the level of ordinary human observation. A technological invention was necessary: The microscope. 5 The Microscope 1st invented at the end of the 16th century (about the same time as the telescope) Originally the compound (2 lens) microscopes were very poor. The best microscope was the single lens apparatus of Anton van Leeuwenhoek. 6

3 The Microscope, 2 Van Leeuwenhoek discovered a multitude of living things too small to be seen with the naked eye: Spermatozoa Other single-celled animals The single-lens microscope is so difficult to use that little research was done by other people. 7 The Cell Compound microscopes became practical in the 1820s and were the standard research tool by German scientists Schleiden and Schwann observed animal and plant cells and declared that cells were the units of life. 8 The Nucleus Later research in the 19th century identified the importance of the nucleus in each cell. Discovered chromosomes in each cell nucleus that divide and reproduce themselves with each cell division. Chromosomes are thought to probably carry the key to cell structure and inheritance. 9

4 Genetics In 1865, the monk Gregor Mendel published the results of his 8-year study of breeding varieties of garden peas. Mendel s work pointed to the existence of units of heredity that operated in pairs and were passed on unaltered from generation to generation, but reconfigured into different combinations in each individual. 10 The Gene In the 1920s T.H. Morgan identified Mendel s units of heredity (now called genes ) as locations on chromosomes. 11 The Gene The search for the gene focused on the chromosomes, which are made of protein and DNA. In 1944, work done by Oswald Avery strongly suggested that the genes lay in the DNA. In 1953 James Watson and Francis Crick worked out the molecular structure of DNA. 12

5 DNA DNA is one of 2 nucleic acids acids found only in the nuclei of cells of living creatures. DNA (deoxyribonucleic acid) has a two strand, helical structure, with a sugar-phosphate backbone on the outside and pairs of bases on the inside holding the structure together. 13 DNA The bases are Guanine, Adenine, Cytosine, and Thymine (referred to by their initial letters, G, A, C, T). Guanine always pairs with Cytosine Adenine always pairs with Thymine Cytosine-Guanine bond Thymine-Adenine bond 14 RNA The other nucleic acid is RNA (ribonucleic acid). RNA is found in the nucleus but not in the chromosomes. RNA comes in more than one form, but all have the structure of a single sugar phosphate backbone and four bases, Guanine, Adenine, Cytosine, and Uracil (replacing the Thymine in DNA). 15

6 Molecular Biology After the discovery of the structure of DNA in 1953, the basics of how DNA contains the genetic code, how it passes it on to other cells, and how that code is used to direct the processes of the body were worked out over the next years. The two main functions of DNA: Self-replication Sending instructions to the cells 16 Self-Replication of DNA The DNA makes a copy of itself every time a cell divides. It does so by splitting down the middle, breaking the bonds between the base pairs. A new strand forms alongside each existing strand with the corresponding base attaching where the base from the other strand had been. 17 Sending Genetic Instructions to the Cells When the body determines that it requires more of something (e.g. a protein) in a cell, the DNA in that cell opens at the part that has the blueprint on making the protein. A strand of messenger RNA forms alongside the opened portion of DNA with the bases that fit against those on the DNA. The RNA migrates into the cell body and provides a template of instructions for the construction of the desired protein. 18

7 Recombinant DNA The complexity of DNA has made it very difficult to study its particular sequences in detail. Even a virus can have as many as 5000 base pairs. A human has more like 100,000 base pairs in its DNA. Breakthroughs in research came in the mid- 1970s with two techniques for working with DNA. 19 Recombinant DNA Cleaving enzymes that have the effect of cutting a piece of DNA wherever it encounters a certain sequence of bases. For example the enzyme ECORI cuts DNA at the sequence GAATC. DNA ligases are other enzymes discovered that rejoin DNA pieces. Thus DNA research had the scissors and paste tools necessary to manipulate DNA and study the results of experiments. 20 Cloning Cloning is the process of producing a strain of DNA and then inserting that DNA into a host where it will replicate. The replicated DNA is called a clone. Cloning as a technique has many uses. For example, it can be used to replicate rare hormones and proteins such as insulin and interferon that have much medical usage. Recently cloning has been taken to far a far greater extent. Whole organisms have been reproduced from DNA taken from other bodies. 21

8 Insulin Insulin is a protein hormone produced in the pancreas that the body uses to regulate blood sugar concentrations. Diabetics have lost the ability to produce insulin and must have an outside source of it. In the 1920s, insulin from cows and pigs was isolated and made available to humans with diabetes. (Though it is not identical to human insulin.) Supply was a major concern since the number of diabetics was on the rise. Cloning insulin became an ideal usage for recombinant DNA technology. 22 The Manufacture of Insulin by Cloning In 1978, Herbert Boyer and colleagues at the University of California in San Francisco created a synthetic version of human insulin using recombinant DNA technology. The DNA sequence representing the instructions on growing insulin was separated and then inserted into the bacterium E. coli. The E. coli then produced prodigious amounts of human insulin. 23 The Biotechnology Industry Boyer set up a company to manufacture and sell the products of Recombinant DNA technology. His company, Genentech, began manufacturing recombinant human insulin. Genentech (stock symbol, DNA) now manufactures a variety of synthetic hormones for the treatment of cancer, heart disease, immune system disorders, and other problems. A large industry with many companies in many countries has followed. 24

9 Transgenics A new Green Revolution. In addition to using Recombinant DNA to grow hormones and other proteins for use in the original species from which they came, the technology has been used to insert genes from one species into another species altogether to make a new hybrid that has desired characteristics. One of the biggest applications of this today is genetically modified foods. 25 Genetically Modified Food Crops may be genetically modified for a number of reasons. Often the reason is to provide a natural resistance to insects, making insecticides unnecessary. Another is to provide tolerance for herbicides, so that they may then be sprayed on the crops to kill weeds without killing the crops. 26 Genetically Modified Food, 2 On the left, an ordinary soybean field infested with weeds. On the right, transgenic soybeans that are herbicide tolerant after the field was treated with the herbicide. 27

10 Genetically Modified Food, 3 Transgenic foods are much more common than one might think. Current estimates are that 60-70% of all food sold in the U.S. contains at least some genetically modified crop. The largest crops: Soybeans 60% of U.S. crop is genetically altered. Soy products are ingredients in many processed foods. Corn 25% of U.S. crop is genetically engineered. Most of this goes into corn ingredients in other foods, or as feed to animals. Other crops: canola, cotton (as a food in cottonseed oil) 28 Cloning Whole Animals In 1997, the sheep Dolly was cloned from an adult sheep. Dolly is an exact replica of its mother the animal from which the cell was taken. 29 Stem Cells Most cells in the body of an adult animal are specialized cells, which have the capacity only to reproduce themselves. Cells that have the ability to divide and give rise to different kinds of specialized cells are called stem cells. At conception, the fertilized egg is a stem cell capable of dividing and becoming every different kind of cell in the adult body. (They are Totipotent. ) In humans, the cells that are produced in the first four days or so after conception are all totipotent stems. At later embryonic stages and even in the grown adult, there are stem cells with limited potential to grow into different kinds of cells. (These are called Pluripotent. ) 30

11 Stem cells, 2 The medical potential of stem cells, both the totipotent and pluripotent is enormous. If stem cells can be isolated, cultured, and then grafted into patients, many degenerative diseases could possibly be reversed. Cells generated from a patient s own stem cells, for example, would not be rejected by the body the way that the cells of donor organs often are. Stem cells could be used to regenerate brain and nerve cells, possibly heart muscle, and many other possible uses. 31 Ethical issues in Biotechnology There are ethical issues all the way along in biotechnology because human beings are capable of manipulating life as never before. Stem cell research raises the issue of where life begins and whether cells from a human embryo should be used for another human s benefit. Present stem cell work concentrates on making regenerative cells for the cure of diseases. But the possibility of cloning whole human beings has to be considered. Dolly was cloned from a stem cell. 32