Ryan+S.

You know that little piece of plastic at the end of your shoe lace? The one that keeps the lace from untangling and fraying off? Well that’s called an aglet, and our chromosomes have a little piece just like it on their tips: it's called a telomere. Telomeres are just meaningless repetitions of base sequences (for example, a human's telomere just repeats TTAGGG), and they are present solely to keep the important genetic material from fraying off, and to make sure chromosomes can’t fuse together. However, as you’ll see, they could play an important role in cancer research and be a key part of biological immortality. This picture should help you visualize the telomeres (the red parts) serving as caps on the tips of a chromosome. The following video was made by ASAPScience, and will give you a very good introduction to the basis of telomeres, and what exactly they do: media type="youtube" key="BkcXbx5rSzw" width="560" height="315" align="center"
 * Wiki Post #1 - Genetics - Telomeres: October 11th, 2013 **
 * What Are Telomeres? **

The Hayflick limit is the number of divisions a healthy human cell population can make, and it’s directly related to the shortening of telomeres. The number of divisions usually made is somewhere between 50 and 60, and it is at this point that the chromosomes will reach the ‘critical length’ and will stop dividing, because any divisions made after this wouldn't have enough meaningless telomere bases to skip over, and could skip the replication of actual genes. When the critical length is finally reached, a cell will usually go through a programmed death known as apoptosis, or change genetically to become cancerous. As you can see in the picture to the right, a telomere on a human blood cell will usually start out with around 8000 base pairs, but each division will swipe away between 30 and 200 pairs, so as we age we gradually lose more and more. **Telomerase **
 * The Hayflick Limit **

As mentioned earlier, telomeres are always getting shorter through division, but they can also grow through the work of the enzyme telomerase. Telomerase works by adding the repeated nucleotide sequences to the end of the present telomeres. Unfortunately, this enzyme is barely present in our body’s somatic cells, and so they’ll age and die just like the rest of our body eventually will.

On the left is a visual of how telomerase works.

**Cancer ** Sadly, one of the few spots that telomerase is very active is in cancerous cells. The telomerase doesn’t allow the chromosomes to reach the critical length, meaning the Hayflick limit doesn’t apply to them, and that they can divide uncontrollably. As long as they’re receiving nutrients they can divide without end. On the plus side, observing this gives us hope of a possible treatment for cancer; if telomerase is somehow blocked, the growth of these tumors can be slowed to a stop, and they could age and die. Also, measuring the abundance of telomerase in the body can help detect cancer. Here is a graph showing relative telomere lengths, over time, of stem/germ cells (blue) who have very active telomerase, normal somatic cells (green) who become cancerous (red), and cells from a person suffering from Progeria (yellow), a disease causing rapid aging. When we talk about the prospect of potentially blocking telomerase from cancerous cells, it also brings up the idea of trying to do the opposite with our healthy somatic cells, and supplying them with enough telomerase to divide long after the Hayflick limit: maybe even forever. I mean, could you render a human being biologically immortal by doing this? No one really knows the answer, but it’s a fun idea to leave you with. __**Further Reading: **__ [] - This is a humorous video by Hank green, on his YouTube show SciShow, all about aging and how we could possibly slow it down. You can skip to about 4:30 if you just want to hear about telomeres. [] - This is an essay written ontelomeres and the role they play in cancer. It dives deeper into some of the topics mentioned in this post. [] - This is an article, accompanied by a video, on how changes to one’s lifestyle could potentially lengthen telomeres and help one avoid cancer. [] - This is a segment off of CTV News, with a little write up, on how people can now get their telomere length tested as a way to reflect on their past and see if they should be making lifestyle changes.
 * Immortality? **

__**References: **__

[] [] [] [|http://www4.utsouthwestern.edu/cellbio/shay-wright/intro/facts/sw_facts.html#] [] []

**Wiki Post #2 - Evolution - Mass Extinctions: December 1st, 2013 ** **What is a Mass Extinction? **  A mass extinction is a geologically rapid decrease in the amount of living organisms on our planet and results in the extinction of many different species in separate biomes. When a mass extinction happens, the diversity on our planet takes a steep drop, and this type of event occurs over tens of thousands of years and has the planet lose over half  of its species to extinction. There are many causes for extinction events, we've seen a number of them in the earth's history and they have drastic effects on evolution.

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This video should provide an extended introduction to the topic of mass extinction, and also brings up the fact that human actions have pushed us into another extinction event which I’ll touch on later. **What Causes Mass Extinction? ** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">There are many natural phenomena’s that we think could trigger, prolong or enhance a mass extinction, and most extinction events seem to be a product of more than one of these possibilities. Here are some of the devastating causes we know of to date;

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__**Trouble in the Oceans**__: As the earth is mostly water and we have many marine species, changes to the oceans can have catastrophic effects. __Sea level falls__ can alter weather and reduce continental shelf area, hurting both aquatic and land animals. __Ocean asteroid impacts__ will dramatically increase ocean temperatures and will subsequently release huge amounts of dissolved CO2 into the atmosphere; spreading around the world with the potential to suffocate animals and lead to global warming. __Anoxic events__ are occurrences where the middle and sometimes even the upper layers of the ocean end up having very little or no oxygen; this is obviously an issue for oxygen dependent marine life. Finally, __hydrogen sulfide emissions__ from the seas have also been theorized to have poisoned both land and sea creatures and to have weakened the ozone layer resulting in fatal UV radiation to organisms.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__**Global Warming/Cooling**__: Whenever the earth’s climate is changed considerably and for a long period of time, it will have serious effects. Warming and cooling of the earth will force species to move to the equator or poles to compensate for the climate change, and will alter the water cycle by having more or less water frozen at the poles. These types of changes allow only for quick adapting species to survive, and will actually lead to a lot of other complications.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__**Plate Tectonics**__: Continental shift can begin or end ice ages, and have major effects on climate by simply changing the wind currents and water cycles. It can also create land bridges or seaways that will change the living conditions of all the animals nearby and mess up food chains.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">__**Out of this World Events**__: __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">Impact events __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;"> of large asteroids or comets can fill our atmosphere with dust, stopping photosynthesis altogether; it can also cause global forest fires, huge tsunamis and/or lead to acid rain (these are basically the same outcomes from the eruption of a __super volcano__), and all of this together collapses food chains. Furthermore, a __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">nearby nova, supernova or gamma ray burst __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;"> could strip the earth of its ozone layer, causing extreme UV radiation exposure.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">These are not the only possible causes for mass extinction, but are some of our major hypothesis, and often one cause will lead to another creating a devastating chain reaction.

**<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">What is the History of Mass Extinction on Earth? ** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">We can identify these events in earth's history by studying fossil records and by looking at the way our world looks today and what could have possibly led to that. Through these practices, it has been proposed and is generally accepted by the scientific community that over the past 450 million years, the earth has experienced 5 major extinctions, known as ‘The Big 5’. Here is a brief description of each and the reasons for which we think each happened;

<span style="font-family: Arial,Helvetica,sans-serif;">

**<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">A 6th Mass Extinction? ** <span style="font-family: Arial,Helvetica,sans-serif;">
 * 1) __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">**The Ordovician-Silurian extinction** __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">: Occurred about 435-445 million years ago; 27% of marine families, 60% of marine genera and up to 70% of species became extinct. It's thought to be a result of continental shift resulting in the formation of glaciers and the falling of sea levels, or a gamma ray burst from a hyper nova.
 * 2) __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">**The Late Devonian extinction** __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">: Occurred about 360 million years ago; 20% of all families, 50% of all genera and 70% of all species became extinct. There are many different theories for the cause of this extinction including asteroid impacts, global cooling, and/or anoxic events.
 * 3) __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">**The Permian-Triassic extinction** __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">: Occurred about 250 million years ago and is known as ‘The Great Dying’; this was the biggest mass extinction event and 95% of all species became extinct! It's thought to have been caused by 1 million years of volcanic eruptions leading to global warming, and under water volcanic activity leading to periods of anoxic events (and the opposite of these, hyperoxia events). The planet was extremely inhospitable at this time.
 * 4) __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">**The End Triassic extinction** __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">: Occurred about 200 million years ago; 23% of all families, 48% of all genera and 70-75% of all species went extinct. It's thought to have been caused by volcanic eruptions resulting in plate tectonic shifting and global warming, but we know less about this extinction event than any other.
 * 5) __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">**The Cretaceous-Tertiary extinction** __<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%; line-height: 1.5;">: Occurred about 65 million years ago (also referred to as the K-T extinction); 17% of all families, 50% of all genera and 75% of all species became extinct. It's thought to be caused by asteroid impacts and/or volcanic eruptions leading to global warming.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Believe it or not, we seem to be in the early stages of a 6th mass extinction event; and it’s being caused by humans. Being an invasive species, destroying habitats, polluting our environment and over harvesting are all activities we humans participate in to the extreme, and are all events that will easily cause extinction in all species but our own. Actually, because of human action, the extinction rate right now is higher than that of the K-T extinction. **<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">How Does all of This Relate to Evolution? ** <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Mass extinctions actually accelerate evolution on our planet. Usually an extinction event will kill off the dominant species in an area, making way for a new species to move in to the now unoccupied real estates, and species with the right abilities to take advantage of this opportunity will. As years pass, species best fit for the new, empty environments will take control of them; and, as a species separates and isolates themselves into the different empty niches, we see rapid diversification through natural selection after mass extinctions.

__**Further Learning:**__ [] - You can watch a TED ED video by Peter Ward on Mass Extinction here [] - If you are interested in the continental shift aspect, you will love this website [] - This article looks deeper into the prospect of the 6th mass extinction [] - Here is a documentary specifically on the Permian-Triassic extinction

__**References:**__ [] [] [] [] []

** Wiki Post #3 - Dynamic Equilibrium - ALS: January 24th, 2014 **

[[image:smithlhhsb122/ALS1.jpg width="142" height="157" align="right" caption="This is Lou Gehrig"]]
<span style="font-family: Arial,Helvetica,sans-serif;"> Becoming progressively weaker, losing muscle mass, having muscle twitches and tightness and having a hard time speaking, breathing and swallowing were all symptoms experienced by MLB great, Yankee superstar, the Iron Horse, Lou Gehrig. Gehrig experienced these with increasing severity from the end of his 1938 season to his retirement at the end of 1939. All these symptoms pointed to one conclusion, and after various tests it was confirmed, Gehrig had amyotrophic lateral sclerosis. The condition now known throughout North America as Lou Gehrig’s disease effects the central nervous system and results in the loss of motor control.

This video should give you an introduction to the disease and its devastating effects:
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**What’s Happening?**
ALS is a disorder in the nervous system that results in the death of upper and lower motor neurons in the brain stem, spinal cord and motor cortex of the brain. Prior to their death, these cells will develop inclusion bodies of proteins usually containing ubiquitin and a protein linked with ALS; SOD1, TAR binding protein, or FUS. Amyotrophic lateral sclerosis is a very tragic disease because it only effects motor neurons. An ALS patient’s sensory neurons will still take information to the brain, which will still be processed by interneurons and signals will still be sent out on how to respond. The issue is that there won’t be many motor neurons alive for these signals to fire through, so individuals with the disease have very limited movements and reactions to the outside world.

**Symptoms/Effects**
Like mentioned earlier, effected individuals will slowly become weaker and lose more and more muscle mass. The abilities to initiate and control voluntary movements are eventually lost, but thankfully eye movement, bladder and bowel sphincters are usually the last to go in the final stages of the disease. The increased severity of symptoms can be divided into three categories;


 * __Early Stages__**: Different patients will have different body parts effected first, but in most cases you’ll first notice obvious all around weakness and either awkward function of limbs or difficulty speaking and swallowing. In time, patients will exhibit all of the above mentioned symptoms along with constant muscle tightness/stiffness, occasional muscle cramps and overactive reflexes.


 * __Middle Stages__**: Depending on the individual, symptoms will get worse at different rates, but as months pass patients will completely lose the ability to use their limbs, swallow and speak. Nevertheless, most are able to interact and move with a monitor attached to wheelchair all controlled by eye movement.


 * __Late Stages__**: In later stages, most patients require being hooked up to machines to help them maintain a healthy body weight and support breathing. Most patients will pass away due to respiratory failure 3-4 years after onset.

**What Can You Do?**
As of right now, there is no cure for ALS, and the treatments are limited but the following options exist;
 * Riluzole is the only drug found to slightly prolong survival, and will give a diseased individual 3-5 more months of life, and delay the need of machine assistance.
 * Many medications are available to reduce pain, fatigue, muscle cramps, sleep disturbances and other small nuisances. There are also drugs available to decrease the amount of saliva/phlegm for patients who have difficulty swallowing and breathing.
 * Therapy can also be sought out to help diseased individuals adapt to their rapidly changing lives, regain some independence and to make the most out of what they can still do.



__Further Reading__: [] - This is the ALS association's website, who are trying to increase treatments and ultimately find a cure [] - Here is a summary of a film made primarily by a sufferer of ALS during his battle [] - This video gives a good run over and visual of how amyotrophic lateral sclerosis does its dirty work [] - Here is a list of frequently asked questions about ALS and their answers

__Resources__: [] [] [] [] []