Study Guide

Genetics In the Real World

  • Biotechnology

    Farm animals producing life saving medicines in their milk. Fluorescent pets. Crops that synthesize their own pesticides or promise to help vitamin A deficiencies in the developing world. Yep, all real stuff, and all the result of one of the most promising fields in biotechnology: genetic engineering. Transgenic species, GE (genetically engineered) animals, or GMOs (genetically modified organisms) are animals or plants whose genetic makeup has been changed by introducing genes from other species (called transgenes) thus modifying aspects of their form or function. Species manipulated in this way have benefited many fields including agriculture, medicine and industry.

    People that suffer from hereditary AT (antithrombin) deficiency do not produce enough antithrombin, a protein in the blood plasma that works as an anticoagulant. During surgery or childbirth, people with this disorder might develop life-threatening blood clots. Under certain medical situations, people suffering from hereditary AT deficiency require replacement antithrombin, usually obtained from human blood plasma. Transgenic goats, however, are able to produce antithrombin in their milk for therapeutic treatment. These goats, bred at GTC Biotherapeutics, have a segment of human DNA coding for antithrombin inserted into their genome. So that this transgene is only expressed in the milk and not in the whole animal, the promoter driving it (basically, the on/off switch for the gene) is from casein – a milk protein. A single goat during a year can produce as much antithrombin as 90,000 blood collections. This is the first product (named ATryn) produced by a genetically engineered animal approved by the U.S. Food and Drug Administration for use in humans (GTC Biotherapeutics, 2010).

    A common genetic manipulation in gene studies involves introducing a fluorescent protein derived from the jellyfish Aequorea victoria. The developers of this technique, Osamu Shimomura, Martin Chalfie, and Roger Y. Tsien, won the Nobel Prize in Chemistry in 2008. The technique allows scientists to study when and where genes might be expressed, as the fluorescent "tag" makes their product visible. For example, using fluorescent-labeled virus strain, it is possible to trace how it reproduces and infects new cells. But such technology also has commercial uses. Pretty much any organism could be made fluorescent by inserting this gene, which has since been engineered from its original green color to include red, blue and yellow variants. The Glofish, sold as a pet, is a transgenic fluorescent zebrafish that you can buy and keep at home.

    Its likely you've had foods containing some sort of genetically enhanced product. Some varieties of the most common crops in the US are genetically enhanced. Corn, cotton and soybeans have increased productivity, herbicide tolerance and insect and drought protection. "Golden rice" is a variety of Oriza sativa genetically modified to produce beta-carotene (the pre-cursor for vitamin A) in the endosperm (edible part of the grain). By adding two genes to the plant's genome, "golden rice" accumulates this vital chemical. Golden rice was developed to help areas of the world affected by VAD (vitamin A deficiency). VAD is responsible for blindness, amongst other health problems, in children, and approximately 1.5 million deaths a year (Golden Rice Humanitarian Board, 2010). Additional projects underway promise to enhance other major crops and hopefully help with health concerns around the world.

    In the future it is likely that genetically engineered organisms will produce vaccines, antibiotics and biofuels, amongst many other needed biological products. This emerging technology, however, has raised many concerns and considerable opposition. Are we interfering with natural evolutionary processes? How safe are products resulting from genetically engineered species? Could there be some unforeseen secondary effects of inserting transgenes? Who owns these species, and how should they be commercialized? As genetic engineering grows and its benefits and drawbacks are further defined, it will be up to you to decide…

  • Pop Culture

    Genetics are a super popular subject in TV shows, movies and even comics. Kind of expected really, because genetics are just perfect for letting the imagination run wild and for generating lots of drama. Here are some popular plots where genetics play a main role and how close to reality these scenarios might be

    Mutant Super Powers

    A genetic mutation gives a person or animal some unique ability. The various heroes and villains in X-Men were born with, or acquired, unique appearances and superpowers. "Beast" was, as a youngster, a particularly large guy with superhuman strength, agility and speed (Marvel, 2010). His unusual characteristics, or "mutations" were the result of his father's exposure to radiation. Despite being teased in school because of his appearance, his abilities made him a great football player. Later on, he becomes a genetic researcher and discovers a "hormonal extract" that causes "genetic mutation." In order to disguise his appearance to stop a villain, he takes the extract himself and mutates into the blue furred beast in the later publications of the comic series.

    In truth however, most mutations have only a tiny effect, or, quite often, no effect at all. Some, however, are detrimental, maybe even lethal—it all depends on where in the DNA the mutation takes place and whether or not it changes the structure or function of the protein the gene codes for. Radiation does often lead to mutations – in fact researchers often make use of this fact to study gene function using simple organisms such as flies. Groups of flies are exposed to radiation that generates mutations in their sex cells which will be passed on to their descendents. After breeding the irradiated flies, their offspring are screened for mutant phenotypes, such as changes in eye color, wing shape, or body pigmentation (all of which have been found using this method). After identifying the genes that mutated, scientists can then study how disrupting their normal function affects development and thus learn about how different genes work together. Also, "Beast's" scientific discoveries are far from any real possibility: to date, no "mutagenic hormonal extract" exists that is capable of physically transforming anyone or anything into a different creature!

    Designer Babies

    Instead of wondering if their baby will be a boy or a girl, or what color her eyes might be, parents just get to order their child with custom genetics to fit their dreams and ambitions. The movie "Gattaca" (1997) is based on this premise. In the movie, human genetic engineering is prevalent, but not accessible to everyone. Genetic makeup defines social class, so people conceived naturally are at a disadvantage. One man's dreams are hindered by his "inappropriate" genotype—so he borrows someone else's to fool the system. The novel "A Brave New World" (Aldous Huxley) also explores certain aspects of designer humans. In a futuristic society, reproduction is fully regulated. Practically no child is conceived naturally; instead babies develop in synthetic setups and their development is tightly controlled.

    In reality, we might not be too far from pre-determining some traits in unborn children. It might not ever be possible to choose every aspect of an individual's characteristics by manipulating her genetic background (remember, not everything is determined by our genes) – but even now it is possible to define a few things. For example, using in vitro fertilization procedures, it is possible to define the sex of an embryo. As it turns out, because in humans the X chromosome is so much larger than the Y chromosome, it is possible to detect simply by the amount of DNA it contains which sperm cells have an X or a Y chromosome.

    By screening and choosing specific sperm cells, it is possible to pre-define the sex of a baby. There may be a specific medical reason for wanting to do so, such as to avoid passing on potentially fatal hereditary diseases such as hemophilia and muscular dystrophy, but there is a growing concern worldwide that the non-medical sex selection of embryos may end up dangerously skewing the proportions of male and female children born in certain countries as a result of cultural biases (Robertson, 2003; Stump, 2011).

    Forensic Shows

    A detective fools a suspect into giving up his DNA by collecting saliva from his discarded chewing gum. The process is quick and easy – the chewing gum goes into a little tube with some colorless liquid, and then into some magical machine that prints out some banding pattern or DNA sequence to compare to the sample collected from the crime scene. It is match! Let's go get an arrest warrant…

    Believe it or not, with current technological advances it is possible to get enough DNA to analyze from the saliva used to affix a stamp. DNA testing is routinely used for paternity testing, victim identification, and conviction, as in forensic shows. The tests take advantage of genetic variation from individual to individual including, amongst others, variation in regions with variable numbers of the same base-pair sequence (variable number of tandem repeats, VNTR), single nucleotide polymorphisms (SNP) and mitochondrial DNA. What the shows often misrepresent is just how long the process takes and how the DNA information might be interpreted. In the shows, the whole process has a couple of steps and appears to take only a few minutes. In fact, there are many steps, and depending on the techniques used for the DNA fingerprinting (and the state of the DNA being used), it might take hours, days, or even weeks to get a result. Also, DNA fingerprinting can exclude with certainty a potential suspect, but only identify a perpetrator with a certain probability.

  • Research

    Sometimes new discoveries in genetics rival some of the best plots in science fiction. Scientists are now able to create an organism with completely artificial DNA capable of life and self-replication. In the spring of 2010, researchers at the J. Craig Venter Institute (JCVI) synthesized the whole genome (a single chromosome of about a million base pairs) of the bacterium Mycoplasma mycoides and transplanted it into recipient cells of a closely related species, M. capricolum. The transplanted, computer-generated DNA was transcribed into mRNA, which encoded proteins, which enabled division into new cells. The artificial DNA was modified from the natural genome of M. mycoides to remove some pathogenic genes in case the bacteria made their way out of the lab (M. mycoides causes infection in goats) and also to include genetic "watermarks". The watermarks are added DNA sequences that have no function for the bacteria but after decoding they translate into various messages, including the names of authors and contributors, a web address, and some meaningful quotes such as "to live, to err, to fall, to triumph, to recreate life out of life" (James Joyce).

    As Dr. Venter himself said at a press conference, this is "the first self-replicating species we've had on the planet whose parent is a computer." The other parent or ancestor was the closely related species whose cells were used to carry the synthetic DNA. It is important to interpret the results of this research with care – while the cell and all its machinery were first generated naturally by bacteria, the inserted manmade DNA is capable of taking over and running these cells. But no living organism was created from scratch, and no new life form was generated.

    However, the potential of these findings is mind-blowing. The group hopes in the near future to produce another synthetic cell carrying only the essential genes for life. From there, other genes with specific functions can be added on: for example, you could "make" cells that produce biofuels, pharmaceuticals, and various other commercial products.

    The making of this synthetic cell raises various issues. Could the creation of synthetic species pose a danger to our environment? How much can we manipulate life? Who can do it and for what purpose? The publication of these research findings immediately spurred concern from environmental groups, re-heated debates over the morality of genetic engineering, and led the government to request the bioethics committee to study in depth the implications of synthetic biology. These issues are unlikely to be solved easily, and discussions will probably continue for many years to come. Keep up with the news for the next episode of the synthetic cell, because current research can be just as exciting as some of the best sci-fi series (if not more so)!