Genetics

Tweaking a gene or two can bring the desired changes in human body but the technique brings along several moral and ethical issues.

You will have a perfect face if that stub of a nose you got from your father is sharpened a bit. Susceptibility to seasonal allergies is another issue that hassles you day in and day out. We all have something which needs to be altered and made perfect. Developments in science may make such modifications a reality through the use of genetic engineering.

However, the technology is still inviting lots of debates and controversies related to its optimum use. Here we discuss the pros and cons of genetic engineering.

Genetic engineering means alteration of your gene structure to replace any dysfunctional gene with a more efficient one. For instance, if somebody is suffering from cancer, his mutated genes can be replaced with healthy ones through genetic engineering. Another use can be to prevent any family disorder from passing on to a child through gene alteration.

Genetic engineering can either happen through intervention in the sperm and egg cells or via introduction of a viral vector carrying the healthy gene into the body of a person.  Not many people know that one of the first uses of genetic engineering was for production of synthetic insulin which has proved to be a great boon for diabetics.

Pros of Genetic Engineering

As explained above, there are several reasons why genetic engineering can work wonders for the human race. Though we have progressed a lot from the times when smallpox, chickenpox and plague used to wipe out entire cities, new and more lethal diseases like cancer, AIDS, cardiac ailments and Alzheimer’s are still a challenge.

Auto immune diseases are another set of disorders which are troubling several people around the world and are still a mystery for scientists.  With genetic engineering, we can hope to weed out these diseases from their roots which means replacing the faulty genes that allow them to exist and flourish in our bodies. Development of medicines specific to genetic makeup of each individual to get the best results can be one of the pros of genetic engineering.

Not only the diseased and hapless but even healthy and sound can look forward to reap benefits of the technique. Scientists are talking about longer lifespans since the ageing process can be stopped by tweaking particular genes. In fact, not only life spans but complete reversal of time – from old age to childhood or youth – may become a reality.

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Cons of Genetic Engineering

Though benefits of genetic engineering may seem like our ultimate dreams coming true, it is not so easy. There are various risks as well as moral and ethical dilemmas associated with the technique right now. Scientists are still experimenting with genetic engineering and some of these attempts have resulted in death of the subjects because there is still no clarity on how and in what way the healthy genes can be introduced in a body. In addition, the risks of making such an alteration are also not known. There can be an inherent capacity in human body to resist any attempt for genetic makeover by making corresponding changes in the genes elsewhere.

The risk of creating a seemingly perfect race is also manifold. Due to diversity of genes, there are some people who are more prone to a certain disease while there are others who are completely resistant to it. Since with the ‘perfect gene’ theory, we will all be genetically same, a new and more lethal disease can finish off the whole human population in one go.

On the other hand, if there are only a few who get this benefit of having a perfect gene, there will be discrimination. A few “mentally and physically perfect” people ruling large number of lesser mortals can be one of the cons of genetic engineering.

Parents will start making a beeline to have a “designer baby” who can bend it like Beckham and sing it like Bryan Adams while having the looks of Tom Cruise.

So is it really necessary for scientists to play God and change the genetic character of people to make them healthy or increase their life spans? Maybe with time and greater knowledge, we get to understand things better. Moral and ethical issues aside, genetic engineering holds a great scope in medical field and restricting the use of this technology only to deal with chronic and deadly diseases can be the solution which helps us all.

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What is a virus?

Viruses are among the simplest organisms on Earth. They are invisible to the naked eye as their size ranges from 20-400 nanometers, 10-100 times smaller than a bacterium. They are made up of at least one protein and a single- or double-stranded nucleic acid enclosed by a protective protein covering called capsid which contains enzymes that allow them to enter their host cell. Their genome is contained in their nucleic acid which may either be a deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) but never both. Because of this, the type of their nucleic acid became the basis of their major classification: DNA viruses and RNA viruses.

Viruses can be considered living and non-living. Non-living in the sense that they  are acellular (not made up cytoplasm and organelles) and cannot carry out basic biological functions such as growth and replication on their own. In order to reproduce, they need to enter a host cell (a bacterium), thus, viruses are obligatory parasitic in nature. While outside a host cell, they remain in a state of dormancy where biological processes are arrested. But once inside their host cell, they replicate at a very fast rate, hence they become ‘living’ entities.

Viral Reproduction

There are two cycles in viral reproduction, the lytic cycle and the lysogenic cycle. The former is considered the main mode of reproduction which eventually leads to the disruption of the host cell thereby releasing viral progeny ready to infect other cells. The latter on the other hand can occur without causing harm to the host cell.

A virus that uses a bacterium to replicate is called a bacteriophage. Bacteriophages can be further classified into two based on the process they use to reproduce. Those that go through the lytic cycle to replicate are called lytic bacteriophages while phages that replicate by means of the lysogenic cycle are called Temperate phages. Lytic phages are named so because at the end of their replication, they lyse or disrupt their host bacterium. Temperate phages in contrast can replicate by incorporating their DNA into their host’s DNA without causing bacterial lysis.[ad#co-1]

Lytic Cycle

This cycle consists of 5 stages – Adsorption, Penetration, Replication, Maturation and Release. A sixth stage called Reinfection can also be part of this cycle.

When a bacteriophage infects a bacterium, T4 for example, it attaches itself to the bacterium’s cell wall using its tail fibers. The protein on its tail fibers enables the virus to recognize and attach itself to specific receptor sites in the bacterial cell wall which includes lipopolysaccharides, teichoic acids, proteins or even a flagellum. The specificity and compatibility of the bacteriophage’s attachment to its host as determined by the type of receptors limit the type of host cell for the bacteriophage. This just means that there are only certain bacteria that can be infected by a particular bacteriophage.

After attachment, the T4 phage releases an enzyme that weakens the cell wall of its host. The weakened area becomes the spot where the phage injects its DNA into the bacterium. Once inside the host, the phage starts to take over its host as it makes great amount of viral proteins and genetic materials (DNA or RNA). The replication in T4 phages specifically involved three phases of mRNA production followed by protein production. When there are enough viral components synthesized, assembly into complete viruses immediately follows. In the case of T4 phages, the protein coded by the phage DNA acts as enzymes for the assembly of new T4 phages. Finally, an enzyme that weakens the host’s cell wall is then released and later on, lysis or disruption of the host bacterium occurs, releasing the newly formed T4 phages.

Lysogenic Cycle

As in the lytic cycle, lysogenic cycle begins with the phage’s attachment to the cell wall followed by the injection of the phage’s genome into its host. However, unlike lytic bacteriophages, temperate bacteriophages do not shut down their host cell. After the genome is injected, it becomes integrated into the host’s DNA and is now called a prophage (phage’s genome incorporated into the bacterial DNA). Since the phage’s genetic material is added with that of the host, it is also replicated when the host cell replicates its DNA and divides. Thus, the viral genetic material is transmitted to bacterial daughter cells at each consequent cell division. The prophage can be cut out from the host’s genome by external factors such as ultraviolet radiation. After being removed, it replicates and produce viral components which ultimately leads to lysis of the host cell.

Differences of Lytic and Lysogenic Cycle

Both the lytic and the lysogenic cycle are means in which a virus reproduce. The main difference of these cycles is that in the lytic cycle, bursting or destruction of the host cell inevitably occurs whereas in the lysogenic cycle, the phage can replicate without harming their host. Another noticeable difference between the two is the number of phages produce after every cycle. More are produced in the lytic cycle whereas there are only 2 in the lysogenic cycle as a result of cell division. Also, the resulting products of the lysogenic cycle can further undergo lytic cycle when triggered by external factors such as radiation. But those that undergo lytic cycle follows each stage until the end solely without any diversion or alternative process from the lysogenic cycle.[ad#afterpost]

Linus Pauling (February 28, 1901 – August 19, 1994) has already established himself as one of the premiere scientists in chemistry when he shifted his focus and became a vital force in genetic and biochemical research during the 20^th century.  His interest and proficiency in chemistry at a young age led to his achievements in the fields of chemistry, quantum mechanics, biochemistry, genetics, and medical research.

Chemistry

While in Oregon State University (OSU), Pauling became interested in the electronic structure of atoms and how they bonded to form molecules. This interest led him to delve into the relationships between chemical and physical properties of substances and their atomic structure. Thus, with this research focus, he became one of the progenitors of quantum chemistry.

His interest in mathematical chemistry and physics continued. He entered graduate school at the California Institute of Technology, with crystal structure of minerals being his primary research interest. He published seven papers on the subject during his post-graduate stay in Caltech and graduated summa cum laude in 1925 with a doctorate degree in chemistry having strong minors in mathematics and physics.

Eager to learn from the greatest scientific minds of the era, Pauling travelled to Europe and studied under Neils Bohr, Arnold Sommerfeld and Erwin Schrodinger. These men were the leading scientists in quantum mechanics, bringing their individual mathematical and physics experience into this new field of science. Quantum mechanics dealt primarily with the inner workings of atoms and their components and how they interacted to form substances, thus, it was an important step in Pauling’s own research on the electronic structure of atoms and molecules.

Building on his experience in Europe, Pauling continued his research into crystal diffraction initially using x-rays but eventually utilizing electron diffraction technology obtained from Europe. His work encompassed charting bond angles as well as atomic arrangements in crystals. He also delved into ionic bonding, confirming the theoretical concept of electron transfer between ionic atoms to form bonds. It was here that he developed “Pauling’s Five Rules” which provided the theoretical framework for defining the structures of complex compounds, particularly silicoids and metals. His research postulated that magnetic properties play a vital role in both covalent and ionic bonding.

Another of Pauling’s major contributions was in the field of electronegativity. He constructed the electronegativity scale with elements having smaller electronegativity being closer in approaching a pure covalent bond. Additionally, he proposed two important concepts in chemistry, bond orbital hybridization and bond resonance. This allowed scientists to account for structural patterns that occurred but were then unexplainable by empirical formula, thus opening the way for theoretical research in structural stability and geometry.

Pauling was the single unstoppable force in chemistry during the era, having the ability to theoretically predict the structure of undiscovered compounds using his “stochastic method”. His experience and knowledge coupled with his creative mind enabled him to visualize new substances based on rules and established patterns. This proficiency in theoretical mathematics on the mechanics of atoms and molecules yielded fifty papers during his five year tenure as a professor at Cal-tech. Due to his work on the nature of chemical bonds Linus Pauling became the first recipient of the Langmuir award for the most significant scientific contribution by a person less than thirty years of age.
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Biochemistry and Genetics

With his background in chemical structures, quantum mechanics and diffraction, Pauling had no difficulty shifting his focus to biological studies during the 1930’s.  His previous work on metallic compounds and crystals gave him a novel approach when tackling the chemistry of biological molecules. This produced the 1940 research on the properties of hemoglobin. His next work on the interactions between antigens and antibodies was the start of his investigations regarding specificity in biochemistry.

Pauling postulated that biological specificity was present at the molecular level, with a molecule of a particular shape fitting into a complementary molecule. This “hand in glove” theory again reaped publications and awards finally leading to Pauling’s proposal in 1946 that the gene might be composed of two complementary strands. Two years later, this idea would form the basis for the alpha helix. Pauling, together with Robert Corey and Herman Brandon proposed that two chains of polypeptides containing complementary strands of amino acids would each coil around each other, resulting in a right handed coil known as the “alpha helix”.

The alpha helix was a step into the search for the structure of DNA. Leading scientists worldwide were vying for the honor of becoming the first to correctly identify DNA’s makeup and structure. Linus Puling was no exception and but for a quirk of fate, he would have had ample chance in the race. Sadly, troubles with his political opinions led the U.S. government to deny him a passport just when he was heading to a scientific convention in England. By chance, this was the same convention where Watson and Crick first saw Rosalind Franklin and Raymond Gosling’s “photo 51”, giving them an idea of DNA’s double helix structure. Pauling put forth his own, triple helix theory based on the limited resources available to him.

Linus Pauling had another significant contribution, this time in the field of molecular genetics. Together with Harvey Itano, S.J. Singer and Ibert Wells, Pauling published a study giving a molecular description to the disease sickle cell anemia. His experience in working with hemoglobin as well as his theory of specificity in biological molecules led him to believe that sickle cells were caused by two complementary sites within an abnormal hemoglobin, thus attracting each other, res Entitled “Sickle Cell Anemia, a Molecular disease” and published in Science, Pauling and his co-authors used electrophoreses to demonstrate the presence of a modified form of hemoglobin in those who have the disease, while also showing that carrier have both normal and modified forms. This paper was the first to exhibit the role of Mendelian inheritance in determining a protein’s physical properties. It showcased the first genetic disease, accurately showing hereditary patterns and the presence of unaffected carriers. It also showed that genes were not limited to expressions of presence and absence of enzymes but could affect protein properties as well.

From chemistry to biology to genetics, Linus Pauling has impacted most of the scientific revolutions in these three fields. He showed that science actually is interdisciplinary and that techniques, methods and knowledge from one branch can be utilized with success in others.

Other Famous Scientists in Genetic Research:

• Barbara McClintock
• Sir Alec Jeffreys
• James D. Watson

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References

• Pauling, Linus, Harvey A. Itano, S. J. Singer, Ibert C. Wells (1949). “Sickle Cell Anemia, a Molecular Disease”. Science 110 (2865): 543–548.
• Nobel Lectures (1964) Linus Pauling Biography, Chemistry 1942-1962, Elsevier Publishing Company, Amsterdam, from Nobel Prize Foundation Linus Pauling Biography. Nobelprize.org. 9 Jun 2011 http://nobelprize.org/nobel_prizes/chemistry/laureates/1954/pauling-bio.html