Thursday, 25 October 2012

Pleiotropically Linked Genes


Pleiotropy is defined as the production of two or more unrelated traits by a single gene. Pleiotropy was first described by Mendel in his 1866 paper but the term was not officially coined until 1910 by Ludwig Plate, German geneticist. Pleiotropy has played a role in multiple theories including senescence, direction of selection, adaption and genetic disease. A major goal in genetics is to determine when pleiotropy is caused by a single gene with multiple products and when a single product is incorporated in many different ways.
It was not until the 1970s when gene sequencing became refined enough to shed light on molecular pleiotropic mechanisms. Current research has explored two questions; how extensive is pleiotropy in the genome and how do common mechanisms of pleiotropy work? Whilst originally it was thought that a change to a gene would have a universal effect on an organism recent experiments conducted by molecular geneticists have suggested that there are a few genes that have an effect on a significant number of proteins when they are changed but the majority of genes have little effect to more than one protein.
Dmitry K. Belyaev, a Russian geneticist, did an experiment with foxes. He bred 35 generations with the focus on a single trait, docility. By the end of the experiment the foxes were docile but major physiological traits had changed. The foxes legs and tails had grown shorter, their ears had grown floppy (like dogs) and vixens were now ovulating much more frequently. Clearly the gene responsible for the behavioural changes had also changed proteins responsible for these physical traits.
Pleiotropy can be antagonistic; one trait will be beneficial and another trait detrimental. High testosterone levels in early life will cause an increased level of fitness but will cause an increase to the risk of prostate cancer in later life. The p53 gene when highly expressed suppresses stem cells reducing the replenishment of tissue but reduces the risk of cancer.
Antagonistic pleiotropy is a reason an organism can never reach perfection in its environment. If a gene is pleiotropic and selection favours high expression for one trait and low expression for a different trait then a compromise must be made; middling expression, causing no benefits and no drawbacks.
As the cost of gene sequencing continues to decrease it is becoming more and more feasible to sequence an individual’s genome. Enabling us with the ability to pre-diagnose and treat people for genetic diseases they are likely to have.

Stearns, F.W. 2010, ‘One Hundred Years of Pleiotropy: A Retrospective’, Genetics Society of America, No. 186, pp. 767-773

Trut, L.N. 1996. Early canid domestication: the farm-fox experiment. American Scientist 87:2:160-159.

Gann, P.H., C.H. Hennekens, J. Ma, C. Longcope, M.J. Stampfer. 1996. Prospective Study of Sex Hormone Levels and Risk of Prostate Cancer. Journal of the National Cancer Institute 88:16:1118-1126.

Aeroponics and Vertical Farming


Aeroponics and Vertical Farming

What if I told you the world’s population would have reached 10 billion people by 2027, which is double the population of 5 billion in the last decade and that this increase is exponential? You may not think much of this, but statistics informs us that in order to support life on Earth, 80% of the world’s farmable landmass is already in use, with 15% damaged by poor agricultural practices. In the near future, we will be presented with issues such as the infinite demand of fossil fuel and food produce facing the challenge of the world’s finite resources. So what is the solution you may ask? Scientists are currently looking into the viability of aeroponics in aid of vertical farming projects in metropolitan areas.  

Vertical farming is not a new concept at all. Rather, it builds on the idea of greenhouses or indoor farming. It has been calculated that to provide an average person with vegetables, 16 square feet of gardening space is required and in good growing conditions, which is more than that will exist in a city environment. To significantly reduce the size of farmland, scientists are changing the method of nutrient delivery to plants, termed aeroponics, in a form of fine mist. This will reduce water usage by up to 90% compared to a conventional garden. This is significant as 70% of the fresh water available in the world is used for irrigation, which would be contaminated by fertilizers, herbicide and silt. This new method will reduce run-off and nutrients can be recycled and monitored to ensure efficient usage. Moreover, aeroponics will also escalates growth rates by more than 25% as oxygen saturation in air is much higher than that of soil. By increasing the carbon dioxide saturation in the system, an additional 40% markedly increase in growth can also be expected. The increase in CO2 levels will also discourage pest infestations and bacterial contaminations, thereby optimizing yields. 

At the same time, there are many technological breakthroughs in lighting that make vertical farming a more viable solution to food demands in the future. Organic light emitting diodes (OLEDs) are able to provide lighting in a spectrum tailored for maximum plant growth. Interestingly, blue light is used for vegetative growth, while red is used for the growth of flower and fruits. By isolating spectrums, it eliminates excessive heat production, while saving electricity and most importantly, it allows us to place lights much closer to plants. Hence, the idea of vertical farming!  

There is a lot of research that still needs to be done, but as you can imagine, the future of vertical farming, with the aid of aeroponics is enormous. Either through organic produce or through genetically modified produce, the possibilities are endless by harnessing the ability to tightly control the growth environment.

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Aeroponics and Vertical Farming

What if I told you the world’s population would have reached 10 billion people by 2027, which is double the population of 5 billion in the last decade and that this increase is exponential? You may not think much of this, but statistics informs us that in order to support life on Earth, 80% of the world’s farmable landmass is already in use, with 15% damaged by poor agricultural practices. In the near future, we will be presented with issues such as the infinite demand of fossil fuel and food produce facing the challenge of the world’s finite resources. So what is the solution you may ask? Scientists are currently looking into the viability of aeroponics in aid of vertical farming projects in metropolitan areas.  

Vertical farming is not a new concept at all. Rather, it builds on the idea of greenhouses or indoor farming. It has been calculated that to provide an average person with vegetables, 16 square feet of gardening space is required and in good growing conditions, which is more than that will exist in a city environment. To significantly reduce the size of farmland, scientists are changing the method of nutrient delivery to plants, termed aeroponics, in a form of fine mist. This will reduce water usage by up to 90% compared to a conventional garden. This is significant as 70% of the fresh water available in the world is used for irrigation, which would be contaminated by fertilizers, herbicide and silt. This new method will reduce run-off and nutrients can be recycled and monitored to ensure efficient usage. Moreover, aeroponics will also escalates growth rates by more than 25% as oxygen saturation in air is much higher than that of soil. By increasing the carbon dioxide saturation in the system, an additional 40% markedly increase in growth can also be expected. The increase in CO2 levels will also discourage pest infestations and bacterial contaminations, thereby optimizing yields. 

At the same time, there are many technological breakthroughs in lighting that make vertical farming a more viable solution to food demands in the future. Organic light emitting diodes (OLEDs) are able to provide lighting in a spectrum tailored for maximum plant growth. Interestingly, blue light is used for vegetative growth, while red is used for the growth of flower and fruits. By isolating spectrums, it eliminates excessive heat production, while saving electricity and most importantly, it allows us to place lights much closer to plants. Hence, the idea of vertical farming!  

There is a lot of research that still needs to be done, but as you can imagine, the future of vertical farming, with the aid of aeroponics is enormous. Either through organic produce or through genetically modified produce, the possibilities are endless by harnessing the ability to tightly control the growth environment.



Evo-Devo Michael Vo s4287578


Harvard’s developmental biologist Cliff Tabin said the ‘fundamental aspect of evo devo is understanding how development is tweaked over time’ (J. Rubin, 2009).
How can a chicken and a human have such similar genetic makeup yet turn out, through development, to be completely different? The answer is in the genes. The embryo is generally the starting point for all species. In figure 3 it shows a number of species from their embryonic stage, to half way through its initial development to its final development before birth. As it develops, different combinations of genes are switched on giving the species different traits. Different factors can change the combination of genes that are switched on. These changes allow the species to adapt and survive depending on the circumstance. The University of Massachusetts published an article describing the environment’s effect on evolution of survival traits.
The Cichlid fish pronounced –sik-lid is ideal example of evolution – it has developed over 1000 new species in the past one million years. The study was conducted on jaw adaptation because the jaw is majorly linked to survival, making it an ideal marker. The study focused on the evolutionary development of the cichlid fish and how their jaws evolved when put in different feeding environments. The fish that were forced to feed from the bottom of the water eventually developed different jaws to the fish that had to feed from the surface of the water. Their individual adaptations were different because of the ways they had to eat. The fish whose only food source was on the bottom of the environment developed short, stout jaws for scraping their food from rocks as opposed to the the long jaws for catching food while swimming, found in the other fish. The article states that “biodiversity is due not only to differences in genes, but to changes in how and when genes are expressed.”(ScienceDaily, 2012).
Even though the fish in the study had the same genetic make-up, their physical development was different due to their environment and food source. What this means it that it’s possible for two creatures with the same or very similar genes to look entirely different when fully developed, even though as embryos they looked incredibly similar. Figure 1 gives an idea of all the variations of the same type of species that were found in different environments, while figure 2 shows 4 lower jaws from different breeds of Cichlid fish.  These two images show how the environment can affect a species shape, colour size and other physical attributes.
Looking at how the environment changes the physical qualities of a species is only one small part of the subject of evolution and development. Other interesting topics describe why bats developed wings, how dogs will eventually grow off its extra toe tail and also how toads/frogs will develop teeth. Other research papers of evo devo can predict distinct qualities of some species just by examining the environment. (Viegas, J., 2010)
Evo devo is a relatively new concept, changing the way scientists look at evolution.



Wednesday, 24 October 2012

Early Research Shows Stem Cells Can Improve Movement in Paralysed Rat



Early Research Shows Stem Cells Can Improve Movement in Paralysed Rat
Just a decade ago, neuroscience textbooks held that neurons in the adult human brain and spinal cord could not regenerate. Once dead, it was thought, central nervous system neurons were gone. Because rebuilding nervous tissue seemed out of the question, research focused almost entirely on therapeutic approaches to relieve symptoms and limit further damage.
However, researchers at Johns Hopkins University recently reported preliminary evidence that cells derived from embryonic stem cells can restore movement in an animal model of amyotropic leteral sclerosis (ALS). It a rapidly progressive disorder destroys special nerves found in spinal cord known as motor neurons. Motor neurons are nerve cells that serve as controlling units and vital communication links between the nervous system and the voluntary muscle of the body. In ALS this motor neuron are degenerate or die, ceasing to send messages to muscles. Eventually, all muscles under voluntary control are affected, and patients lose their strength and the ability to move their arms, legs, and body which ultimately lead to paralysis. When muscles in the diaphragm, and chest wall fail, patients lose the ability to breathe by themselves, need to depend on ventilator support. Most people with ALS die from respiratory failure, usually within 3-5 years from the onset of symptoms. This cause is largely unknown, and there are no effective treatments.
In this study, the researchers used a mice model of ALS to test for possible nerves cell-restoring properties of stem cells. The rats were exposed to Neuroadaped Sindbis virus (NSV), single stranded RNA virus that specifically infects the central nervous system and destroys the motor neurons in the spinal cord. Rats that survive are left with paralysed muscles in their hindquarters and weakened back limbs. Scientists assess the degree of impairment by measuring the rats movement, quantifying electrical activity in the nerves serving the back limbs, and visually judging extend of nerve damage through a microscope.
The researchers wanted to see whether the stem cells could restore nerves and improve mobility in rats. Because scientists have had difficultly sustaining stem cell lines derived from rat embryos, the investigators conducted their experiments with embryonic germ cells isolated from human fetal tissue. These cells can produce unchanged copies of themselves when maintained in culture, and they form into clumps called embryoid bodies. Under certain conditions, research has shown that the cells in the embryoid bodies begin to look and function like neurons when subjected to specific laboratory conditions. The researchers had an idea that these embryotid body cells in their nonspecialized stage might become specialised as replacement neurons if placed into the area of the damaged spinal cord. So they carefully prepared cells from the embryoid bodies and injected them into the paralysed rats that had their motor neurons destroyed by the NSV.
To test this idea, the researchers selected from laboratory culture dishes barely differentiated embryonic germs cells that displayed the molecular markers of neural stem cells, including the proteins nestin and neuron specific enolase. They grew these cells in large quantities and injected them into the fluid surrounding the spinal cords of partially
 
Figure1. Neuroadapted Sindbis virus causes progressive lower motor neuron in rats. A, progressive kyphoscoliosis (left) and then hind limb paralysis (right) develop in rats after intracranial of 1000 pFU of rat-adapted Sindbis virus (raNSV)
paralysed, Sindbis-virus –rats.
The response was impressive. Three months of after the injections, many of the treated rats were able to move their hind limbs and walk, while the control rats that did not receive cell injections remains paralysed. Moreover, at autopsy the researchers found that cells derived from human embryonic germ cells had migrated throughout the spinal fluid and continued to develop, displaying both the shape and molecular markers characteristic of mature motor neurons. The researchers are quick to caution that their results are preliminary, and that they do not know for certain whether the treatment helped the paralysed rats because new neurons took the place of the old, or because trophic factors from the injected cells facilitated the recovery of the rat’s remaining nerve cells and helped the rats improve in their ability to use their hind limbs. Nor do they know how well this strategy will translate into a therapy for human neurodegenerative disease like ALS. And they emphasize that there are many hurdles to cross over before the use of stem cells to repair damaged motor neurons in patients can be considered. However, researchers are very excited about their results, which, if confirmed, would represent a major step toward using specialized stem cells from embryonic and fetal tissues sources to restore nervous functions.
Reference
1.Kerr, D.A., Llado, J., Shamblott, M., Maragakis, N., Irani, D.N., Dike, S., Sappington, A.,Gearhart, J., and Rothstein, J. (2006), Human embryonic germ cell derivatives facilitate motor recovery of rats with diffuse motor neuron injury