Question: What are the differences and similarities between cloning and GMOs?
Answer: What every living thing has in common is that all are made up of one or more cells, and all cells contain DNA. Just as a blueprint gives the instructions for building a house, DNA gives the instructions for “building” living things, such as animals, plants, tiny microbes, and people. What makes a plant different from an animal, or one individual of the same species different from another one, is that each contains different “instructions” in their DNA. These instructions are called genes.
Sometimes different individuals have identical DNA. We would say that these are clones of one another. An example of this is identical twins, who are often very hard to tell apart. Their traits (e.g. eye colour, hair colour, height, unique shape of their nose) are the same because their genes are the same.
Clones of plants and animals can be made artificially, and are especially useful in agriculture. Farmers have noticed over thousands of years that not all the plants they grow or animals they breed are the same because they have different traits. Let’s say a farmer found a plant that had particularly good traits, for example it grew fast, gave a lot tasty fruit, needed less water, or was resistant to known plant diseases. This plant could be cloned to produce many more plants with the same traits. It is also possible to clone animals, but in practice, this is difficult. People have tried to clone several domestic and farm animals, and even endangered animals. Cloned plants and animals are basically “identical twins” of the original, just grown or born later.
Genetic modification, on the other hand, is a way to transfer the gene for a specific trait directly from one lineage of plant (or animal) to another. Take the example of a trait for resistance to a virus causing disease in plants. In conventional breeding, a farmer could use plants that are resistant to the virus as “parents”, and some or all of the progeny plants will also be resistant to the virus. This has been done for thousands of years. This old-fashioned way of doing things works, but it is very slow because you have to wait for plants to grow, and then repeat this many times until you get just the right plants consistently.
There are newer ways to introduce a new or useful trait into a plant. It is even possible to transfer genes from one species to another using genetic engineering. For example, a species of bacteria that lives in soil called Bacillus thuringiensis produces a substance that is toxic to insects. The gene for that toxin has been transferred to some plant crops, such as corn or cotton. The modified plant lines are essentially the same as other plants of the same species, except that they are resistant to insects. Both conventional breeding and genetic engineering methods cause changes in the genes (DNA) and so can be used to produce genetically modified organisms, also known as GMOs. A good example of conventional breeding applied to animals is the many dog breeds that have been produced over hundreds of years.
To summarize, in clones all DNA is identical, so all their traits are almost identical. GMOs contain one (or many) new gene(s) to give new traits that the plant or animal did not have before.
Jennifer Holtzmann, Ph.D.
Scientific Evaluator, Evaluation Division
Bureau of Microbial Hazards, Food Directorate
Health Products and Foods Branch, Health Canada
Ask a Scientist: Smoking
Question: I’m 60 years old and have smoked a pack of cigarettes since I was 14. I’m in great health as attested to by almost monthly tests for the past 10 years. I have none of the symptoms people connect with smoking. I look younger than most people my age (I’ve just started getting grey hair this past year). I’m not coughing or hacking. My wife is a jogger and I used to go with her. I ran the distance with her but eventually stopped because she was too slow for me. The only thing I can think of, and it may seem far-fetched, is that I immigrated to Canada from England. Everybody knows that the whole world outside North America smokes and they live longer than we do. If the above is pertinent, it leads to a followup question: what are we doing wrong?
Answer: In fact, the statistics are a little different than you suggest.
According to the World Health Organization’s latest report (http://www.who.int/tobacco/global_report/2011/en/index.html) smoking rates vary widely by country from (3% to 55%): in 2009. Canada is among countries with low daily smoking rates at 14% together with the United States and the United Kingdom at 16%.
According to the Organization for Economic Co-operation and Development, Canada is in the top 10 in the world in terms of life expectancy. The United Kingdom is currently in the top 20, and the United States is in 26th place. Therefore, Canadians born this year are expected to live longer than people born in most other countries. Research also shows that Canadian smokers have a life expectancy that is 7 (males) to 10 (females) years less than the population as a whole (Baliunas D, et al. Smoking-attributable mortality and expected years of life lost in Canada 2002: Conclusions for prevention and policy – available from Chronic Diseases in Canada, 2007;27(4):154-162.)
Even if individual differences in physical fitness, well-being and life expectancy among people can be explained by factors such as lifestyle (e.g., smoking), genetic factors or access to health care, it remains that each day, 100 Canadians die of a smoking-related illness such as cancers, cardiovascular diseases and respiratory diseases (http://www.hc-sc.gc.ca/hc-ps/tobac-tabac/legislation/label-etiquette/mortal-eng.php). Thus, smoking is responsible for more deaths of Canadians than high blood pressure, being overweight or obese, or physically inactive.
For information and advice on quitting smoking, please visit Health Canada’s website at http://www.hc-sc.gc.ca/hc-ps/tobac-tabac/quit-cesser/index-eng.php