HUMAN PROTEINS FROM GENETIC ENGINEERING OF ORGANISMS

Transcription

1 HUMAN PROTEINS FROM GM BACTERIA Injecting insulin is an everyday event for many people with diabetes. GENETIC ENGINEERING OF ORGANISMS involves transferring genes from one species into another. Genetic engineering is currently being used to make medicines, produce food and create mosquitoes whose offspring die before reproducing. SPECIFICATION CONTENT Old: understand how human proteins can be obtained from engineered bacteria, eg human insulin. New: students should be able to understand genetic engineering to include: the basic techniques used to produce human insulin (for the treatment of diabetes) transfer of a human insulin gene into a plasmid of a bacterial cell to form a modified bacterium which can then be cultured in a fermenter to produce human insulin; and the advantages of producing human insulin (and other products) by this method, exemplifying how and why decisions about science are made. STARTER Play the DNA model race (see overleaf). Working in groups of 4, students are given ten minutes to make the longest chain of model DNA they can. Organise the bases (jelly tots) and sugar and phosphate groups (marshmallows) on plates at the front of the room. STIMULUS Demonstrate genetic engineering of bacteria to produce human insulin using the DNA models or the animation ( diabetes/diabetes6.cfm). Read the concept cartoon together. Give students time to discuss their answers in groups of 4. They may agree with more than one person on the page. QUESTIONS Allow some individual thinking time following the concept cartoon discussion. Ask students to write a question for enquiry on a post it note. Working in the same groups as before, share questions and select one to write on an A4 page and place in the centre of the circle. To select the question for enquiry, ask everyone to close their eyes and vote for only one question. The questions are tackled in order from most to least votes. ENQUIRY Make the target that the class set last time visible in the centre of the circle. EVALUATION Exit tickets: students fill in and hand in at the door on their way out. NEXT STEPS Insulin Give each student the Agros product advertisement and ask them to design and prepare the instruction sheet to accompany the toy, using what they know about genetic Images courtesy of the Wellcome Library [ 1 ] Resource for Teachers

2 THE MODEL DNA DNA IS SWEET R A C E Your task is to make the longest chain of model DNA in the class in 10 minutes. Pink marshmallows represent phosphate groups, white marshmallows represent deoxyribose (sugar) groups. Four colours of jelly tot sweets represent bases: yellow is adenine (A), orange is thymine (T), green is guanine (G) and purple is cytosine (C). Toothpicks and string represent bonds. When building your DNA, remember that: - the backbone is made of a repeating pattern of a deoxyribose group attached to a phosphate group; - bases are attached to the deoxyribose groups; - adenine always pairs with thymine; - guanine always pairs with cytosine; and - DNA found in cells is a clockwise spiral helix (if you put your right hand in front of you with the thumb pointing up, your fingers are the direction of the sugar-phosophate backbone.) To think about: What are the limitations of this model? What are the strengths of this model? How could you improve this model? Can you use this model to explain the triplet code for making proteins? Can you use this model to show how genetic engineering is done? The DNA double helix made from sweets. [ 2 ] Resource for Teachers

3 MODELlING G E N E T I C ENGINEERING Strands of students sweet DNA may be used to model genetic engineering. Create two long chains of DNA using all groups models from the model DNA race. Connect the ends of one strand so that it represents a. The remaining long chain will represent a strand of human DNA. The human gene for producing insulin is required. Using a pair of scissors labelled restriction enzyme, cut out a section of DNA from the human chain to represent the gene for insulin. Cut into the plasmid, insert the human insulin gene, and close the plasmid again. Explain that this is inserted into a bacteria cell (where time and creativity allow, a model bacteria cell can be made), where the code tells the bacteria how to make insulin. The engineered bacteria are allowed to grow in fermentation vessels. They are then harvested and the cells broken to release insulin. This is then purified and packaged for human use. Highlight weaknesses in the model, e.g. the lengths of DNA short in comparison to the number of base pairs found on a human chromosome/ and does not show the mechanism of insulin production. The future of insulin production: GM safflower? [ 3 ] Resource for Teachers

4 MAKING HUMAN PROTEINS FROM GENETICALLY MODIFIED BACTERIA Who do you agree with? Why? T h i s i s a g r e a t w a y t o m a k e i n s u l i n. Y o u c a n m a k e l o a d s o f i n s u l i n a n d s a v e l i v e s. P l u s i t i s h u m a n s o i s l e s s l i k e l y t o c a u s e allergic reactions. I don t t h i n k i n s u l i n s h o u l d b e m a d e l i k e t h i s. I t i s s i c k t o p u t h u m a n g e n e s i n a n y l i v i n g t h i n g - e v e n b a c t e r i a. bacteria cell plasmid restriction enzymes cut the h u m a n g e n e i n s e r t e d i n t o engineered plasmid inserted into bacteria human cell e n z y m e s c u t o u t desired gene from DNA I think the g e n e f o r m a k i n g i n s u l i n s h o u l d b e d i r e c t l y i n s e r t e d i n t o p e o p l e w i t h d i a b e t e s. I f w e g e n e t i c a l l y e n g i n e e r b a c t e r i a, why not humans? engineered bacteria make human insulin I t h i n k s c i e n t i s t s s h o u l d w o r k o n m a k i n g o r g a n s f r o m s t e m c e l l s. A p a n c r e a s t r a n s p l a n t. would permanently solve the problem. [ 4 ] Resource for Teachers

5 EXIT TICKET What did you learn during this lesson? What happened during the enquiry that helped you to learn? What do you need to find out now? [ 5 ] Resource for Teachers

6 Genetic engineering A glimpse into the future? Design the information sheet to show how this protein builder kit works, based on your knowledge of how insulin is produced. Some other proteins currently made this way are human interferon (used to treat some cancers and hepatitis) and human growth hormone (used to treat growth disorders in children). Include and explain the following key words: gene, plasmid, DNA, bacteria, fermenter, restriction enzymes, extraction, purification, human. Also include the advantages of producing proteins in this way compared to alternative methods. Agros > Store Locator My trolley > Contact Us > More biotoys Nanobot sets Synthetic life generators Intelligent machines Fun with numbers Space travel accessories Meal pills Sale Protein builder kit approved by Read reviews (11) PROTEIN BUILDER Make your own human protein with our new science set Back in the 2010 s, people dreamed of being able to make their own proteins to treat diseases resulting from a deficiency of a protein. No more Why be dependent on big pharmaceutical companies for your medical needs when this kit enables you to make the protein you require at home? Contains bacteria restriction enzymes fermenter Not supplied human cells NOT YET AVAILABLE: PRE-ORDER ONLY [ 6 ] Resource for Teachers

7 the information GM bacteria Genetic modification (GM) Genetic modification or engineering enables a gene found in one species to be transferred to another species. It produces a unique set of genes in an organism. The insulin secretions in the pancreas applications of genetic engineering include making organisms that can produce medicines for humans, e.g. bacteria that can make human insulin and goats that can produce human antithrombin (a protein that prevents blood from clotting) in their milk. Human insulin Insulin is a hormone produced by the pancreas. It tells your body when to move glucose from your blood into cells. Your liver blood sugar levels may rise dangerously high. In some cases, diabetics can control their blood sugar by controlling their diet. In other cases, they need to inject insulin. Sourcing insulin Insulin was initially sourced from the pancreas of animals (including pigs and cows) slaughtered for meat. However, more insulin was needed than could be produced in this way, and also animal insulin is slightly different to human insulin. It caused allergic reactions in about 5% of people treated. Using GM bacteria In the 1980s, bacteria were first engineered and used as mini factories to make insulin. This insulin was injected into volunteers with diabetes. The diagram (below) shows how E. coli bacteria are used to make human insulin. To produce the quantities required, the bacteria are grown in a nutrient bath in sealed fermentation vessels. This must be done in very hygienic conditions. plasmid bacteria cell The future Clinical trials are currently underway for insulin produced by modified safflower plants. This is a way of producing plasmid DNA insulin more cheaply than with bacteria, but some people are concerned with the release of GM safflower plants into the wild. Gene therapy (when a person s genes are modified using a virus to deliver the required gene to target cells) may also be used in the future. It has shown signs of working in research involving other animals. restriction enzymes cut the E. coli are engineered to make insulin h u m a n g e n e i n s e r t e d i n t o engineered plasmid inserted into bacteria cells convert excess glucose into glycogen. In people with type 1 diabetes, the pancreas can t make enough insulin. This means that human cell e n z y m e s c u t o u t desired gene from DNA engineered bacteria make human insulin [ 7 ] Resource for Teachers