Back To CourseHigh School Biology: Help and Review
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Erika has taught college Biology, Microbiology, and Environmental Science. She has a PhD in Science Education.
Humans have been manipulating the gene sequences of organisms for thousands of years by selecting organisms with the traits that we desire. Modern genetic manipulation involves scientific procedures to add new DNA to or silence gene sequences in an organism. The ability to change an organism's genome is very controversial, especially when it comes to the impact it has on human beings.
Genetic manipulation is, in essence, a process done to manipulate the genome of an organism in order to produce desired traits. In the past, this was achieved by selective breeding. Selective breeding can be described this way: an animal or plant would be born with a desired trait, and a farmer would breed this animal or plant to produce more organisms with that trait. Selective breeding is why we have such a huge variety in breeds of dogs. Selective breeding is also why we have cabbage, kale, broccoli, cauliflower, and Brussels sprouts.
As shown in this image, each of these plants is a variation or cultivar of wild mustard ('Brassica oleracea'). Each cultivar was bred for thousands of years for specific features; cauliflower and broccoli were bred for their ability to produce flowering heads. The features seen in each cultivar were the results of naturally-occurring genetic differences found in the genome.
The chickens we buy in the grocery store are nearly four times the size of the chickens available in the 1950s, shown in the image here.
This growth spurt is the result of selective breeding of a particular strain of chickens and improved nutrition. The strain of chicken, which was discovered in the 1950s, naturally had the ability to grow faster and larger than other chickens as a result of a mutation in its genome. While modern practices of feeding animals growth hormones and antibiotics are controversial, they do not modify the organism's genetics and are not considered genetic manipulation.
Selective breeding is very inefficient because it is left to chance. In order to cultivate an organism with a new feature, you have to wait for the feature to occur spontaneously. Modern genetic manipulation makes breeding plants and animals with the desired traits more efficient. It uses genetic engineering to build the genes to give an organism the desired traits and uses biotechnology to introduce the trait into the genome.
Both genetic engineering and selective breeding are considered genetic manipulation. Genetic engineering puts the power of manipulation in the hands of mankind because scientists manipulate the DNA themselves. The ability to manipulate the genome and gene expressions of organisms requires scientists to first develop the tools to manipulate DNA, and then develop methods to introduce DNA that has been modified into the organism's genome.
The first step toward being able to manipulate or engineer new genes was the discovery of DNA ligases and restriction enzymes. Think of creating a modified gene as a super fancy kindergarten collage project; you will need scissors and glue. Restriction enzymes are like molecular scissors that can cut DNA. DNA ligases are like molecular glue - they can be used to glue DNA sequences back together.
Genes from different organisms that have been cut and pasted together are called transgenes. An organism whose genome contains a transgene is considered to be transgenic. In the news, transgenic organisms are often referred to as genetically modified organisms or GMOs.
Transgenic animals have uses in research, the medical field, and agriculture. If you drink lactose free milk, you are drinking milk from a transgenic cow that was engineered to produce less lactose in their milk. In humans, genetic manipulation is called gene therapy, and much of the research is aimed at fixing genetic disease.
Since the discovery of restriction enzymes and DNA ligase, the knowledge of the entire genome of many organisms has been sequenced, including humans. This allows scientists to know exactly which gene sequence they need to change or silence in order to give an organism a new trait or silence a harmful trait that causes a disease.
Genetic manipulation was used to create transgenic apples that do not brown and rice that produces increased vitamin A. Researchers have also created transgenic plants with novel genes that would deliver vaccines against diseases such as cholera or rotavirus. Genetic manipulation also allows scientists to explore the treatment of genetic disease by changing the genome of affected individuals.
Modern genetic manipulation is more controversial than selective breeding because it allows humans to have control over which traits are seen in an organism. In the early days, gene manipulations were performed on bacteria and other single-celled organisms that were only of interest to scientists.
Ethical issues about genetic manipulation began to arise when we started making changes to organisms that are of interest to people and the general public. There are many good things that come from genetic manipulation of organisms, such as improved health and quality of lives. For example, Golden Rice (GR), which has been enhanced to produce vitamin A, eliminates vitamin A deficiency in countries where famine is a problem.
Our understanding of the human genome and genetic engineering also allows for the potential to eliminate genetic diseases, such as sickle cell anemia, hemophilia, and cystic fibrosis.
However, there are potential consequences for the use of genetically modified organisms. When discussing the use of transgenic organisms, you have to consider the impact it has on human health and the environment. For example, in 2008 the first transgenic animal, The GloFish (shown here), became available for purchase by the public.
In the U.S., only California has banned these animals because the impact they could have if released into the wild is unknown. The impact of invasive species is well established. Consider what happened with boa constrictors and pythons in the U.S. GloFish may seem nonthreatening, but if they can outcompete native species for resources, they will impact the environment. The same can be said for any transgenic organism. If the genes from a transgenic organism are introduced into the environment, the genetic diversity found in nature will be affected
Manipulating genes in humans conjures up images of Nazi Germany or movies like Gattaca, where your status in society is determined by your genetic makeup. There are federal, state, and private laws that regulate the kinds of research scientists can do to ensure the safety of transgenic organisms and gene therapy.
Additionally, scientists own their work. Scientists can patent transgenes they create. If a transgene that cures a human disease is patented, people who cannot afford treatment may not have access to the cure. The ability to afford access to a better life becomes determined by social-economic status, which is an ethical issue and furthers the controversy.
To recap, genetic manipulation is a process done to manipulate the genome of an organism in order to produce desired traits. In the past, this was done through selective breeding, which is when a desired trait is witnessed in an organism, and humans then breed that organism in hopes of that trait being passed down.
Nowadays, technology has allowed humans to become adept at cutting and pasting genes from different organisms to create desired effects in a certain organism, including humans. These are known as transgenes. Other methods include gene sequencing, which involves the mapping of an organism's genome.
Genetic manipulation isn't without its controversies, however. Modern genetic manipulation is more controversial than selective breeding because it allows humans to have control over which traits are seen in an organism. Other than the idea of a transgenic creature affecting the genetic diversity of the environment, there are other potential societal consequences as well that wouldn't feel too out of place in a dystopian sci-fi film.
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Back To CourseHigh School Biology: Help and Review
36 chapters | 570 lessons