Brooke+T.

// Wikipost #1, 2/28/14 //
 * __Dominant and Recessive Inheritance__ **

There are various ways in which a genetic condition can be inherited. We can figure out the odds of a child developing a certain condition depending on whether it is dominant or recessive, and which parents actually posses the faulty gene. These conditions or disorders can be present in autosomal (first 22) chromosomes or the X chromosome. If a mutation occurs in one of the first 22 chromosomes, it is classed as 'autosomal'. If the mutation occurs in the 'X' chromosome, it is then classed as 'X-linked'. Also, dominant and recessive aren't always used only in the context of mutations, but we also have traits, such as eye color, which can also be classified as dominant or recessive. Today we will take a further look into autosomal dominant and recessive, as well as X-linked dominant and recessive, while the video touches more on traits.

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 * Recessive and Dominant Traits **

This video is a simple and good way of explaining how dominant and recessive traits work. Traits work the same as disorders and conditions, the only difference from now on is the autosomal and X-linked, the recessive or dominant context is generally all very similar.

In order for a autosomal recessive condition to develop, both genes in a pair must be abnormal.If by chance only 1 of the 2 are faulty, then that person is now considered a 'carrier'. For example, if both birth parents carry a recessive condition, then a child has a 25% chance of inheriting and developing it, and a 50% chance of becoming a carrier. If only 1 parent carries it, the child has a 50% chance of becoming a carrier, but there is no chance that they will develop the condition. This is why some conditions will sometimes skip generations. Recessive conditions are also the reason why it is not recommended that people who are related have children together. If you are related, there is a higher chance that you both carry the same faulty gene, and that a child will receive both of them and develop the condition. An example of an autosomal recessive condition would be Cystic Fibrosis. In this diagram, we see how a recessive trait is passed from parents to children. Each parent has the abnormal gene. 2 of the children became carriers of the trait, but did not develop it. 1 child did not inherit the trait at all; they did not develop it and are not a carrier. The last child was the 25% chance of developing the trait.
 * Autosomal Recessive **

For an offspring to develop an autosomal dominant condition or trait, only 1 of the 2 genes in a pair must be faulty. This makes the odds much higher for developing it. There are no 'carriers' for dominant conditions; you either get it or you don't. For example, if one of the two parents has the dominant trait or condition and the other doesn't, all of their children have a 50% chance of inheriting and developing it the same trait or condition. An example of a autosomal dominant condition would be Huntington Disease. In this diagram we see how a dominant trait is passed from parent to children. Only one of the two parents contain the faulty dominant gene. Out of the 4 children, 2 develop the trait while the other 2 don't, which explains the 50% chance of inheriting and developing it.
 * Autosomal Dominant**

X-Linked recessive conditions are inherited through the X chromosome, and posses many of the same characteristics as autosomal recessive. We know that males have an X and Y chromosome, while females have two X's; because males only have one X, they only need one faulty X chromosome to develop the condition. There are many scenarios that can occur depending on if the mother or father has the abnormal X gene. Some examples of X-linked recessive conditions would be Haemophilia, Duchenne and Becker types of muscular dystrophy.
 * X-Linked Recessive**

Example 1: One of the mothers X chromosomes are abnormal. Here we know that a girl has no chance of developing the condition because there is only one faulty X recessive chromosome, and a girl would need two. 25% chance of a healthy boy 25% chance of a healthy girl 25% chance of a boy who will develop the condition 25% chance of a girl who is a carrier This diagram further explains example 1, where the mother has only one recessive abnormal gene. Example 2: Mother has one faulty X chromosome (carrier), and father has the condition (affected, one abnormal X). A girl now has the chance to develop the condition because there are two faulty X chromosomes that she could inherit. 25% chance of a healthy boy 25% chance of a boy who will develop the condition 25% chance of a girl who is a carrier of the condition 25% chance of a girl who will develop the condition

Example 3: Father has the condition (affected, one abnormal X). 100% chance of a healthy boy 100% chance of a girl who is a carrier, but will not develop the condition

Example 4: Mother has condition (two abnormal X's) and father has condition (one abnormal X). 100% chance of all children developing the condition

Occurs when one abnormal gene of an X chromosome from a parent is capable of causing a condition or disease to be developed in their offspring. This way of inheritance also comes with many scenarios. There aren't many, but an example of a X-linked dominant condition would be Rett syndrome.
 * X-Linked Dominant**

Example 1: Father has the condition (one abnormal X). Here we know that no son will have the condition, because they must receive the Y from their father, not the X. 100% chance of daughter with condition 100% chance of son without condition This diagram further explains example 1, where the father has the abnormal gene. We can see why that no male offspring will be affected, while a female will always be. The father only has one X chromosome, and his daughter will always receive it.

Example 2: Mother has condition (one abnormal X) 25% chance of a daughter without the condition 25% chance of a daughter with the condition 25% chance of a son without the condition 25% chance of a son with the condition

__**Further Reading**__ If you want to read a little more about the topics above, this website explains each one very well!

[] < Autosomal Recessive [] < Autosomal Dominant [] < X-Linked Dominant [] < X-Linked Recessive

__**Sources**__ [] [] [] [] [] [] [] [] []

__**How Snakes Lost Their Legs**__ //Wikipost #2, 5/3/14// Evolving to the point of losing limbs is said to be common among lizards. It may be kind of funny to picture, but it is true that many of the ancestors of the slithering snakes we see today use to have legs. Its still not exact whether snakes evolved from a lizard that burrowed on land or swam in the ocean, but for either scenario the presence of limbs would not be that useful. Researchers believe that the limbs of snakes either started to grow more slowly or for a shorter period of time, until eventually there was virtually nothing left of them. Like I said above, the first theory of why snakes lost their legs is that they descended from a type of lizard that burrowed itself in the ground. This one actually makes more sense to me, because I feel like its more common to see snakes on the ground, under rocks and logs, etc. In this case, it would only be logical that limbs would be a nuisance to have and not useful at all, as they would disturb their way of getting around. Therefore the limbs would slowly regress over time with only beneficial impact on the snake itself. In other words, they evolved to be better suited for their environment.



The picture on the right above shows how some lizards and snakes have very similar long body type, while the one on the left shows the basic theory behind the evolution of leg loss; the lizards burrowed underground in some tight spots where limbs would get in the way. The lizards adapted to this environment, which led to the loss of their limbs.



The photo on the left is a 95 million-year-old snake fossil showing a preserved hind leg. The second hind leg is not visible, but after further x-rays of the fossil scientists were able to confirm that the second leg is simply hidden behind its body. The photo on the right is a close up of that same hind leg structure.

After looking at the x rays, scientists could see that the limbs that the snake possessed has neither foot or toe bones; it was simply the leg structure. They concluded that this snake had already began to evolve. The evidence that we have today also suggests that snakes began to evolve less than 150 million years ago.

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This video shows how some snakes today still have evidence present that their species use to have limbs and how they have adapted. I should also note that some snakes today, like the boa and python, still have small "spurs" that could be mistaken for leftovers of their ancestors, when really they use them during sexual reproduction. Scientists believe that there are still some types of lizards that will eventually lose their limbs or that are still in the on going process of it, depending on what kind of environment they must adapt to.


 * Further Reading**

[] [] [] <-- Interesting theory from a religious point of view []<-- Further explains the type of snake seen in the video above [] [] []
 * Sources**

__**The Immune System**__ Wikipost #3, 07/06/14 Your immune system is a defense mechanism that your body has to fight off bacteria, virus, toxins and other things that are always trying to invade your body. To really understand the power of your immune system, look at it this way: when something dies, all of its bodily systems shut down with it, including the immune system. After just hours of being inactive, the body will be taken over by many different bacteria, parasites, etc. Your immune system is a complex thing that works around the hours to keep you healthy, therefore it would only make sense that how you treat your body will affect the performance of things in it, including the immune system. The immune system is made up cells and organs that specialize in fighting off harmful factors that may enter the body. Ever notice that some people get sick a lot more than others? It's true that everyone is slightly different, but they might be a direct problem for their own immune system. Lets take a look at some lifestyle factors that can have a major affect on the performance of your immune system.

__Spleen__ The spleen is the largest lymphatic organ and it contains white blood cells. It also controls the amount of blood on the body as well as disposes of old blood cells __Lymphocytes__ Lymphocytes are small white blood cells that help defend the body against diseases. There are two types: B-cells and T-cells. B-cells make antibiotics that defend against bacteria and toxins, while T-cells attack and destroy infected or cancerous cells. __Thymus__ The thymus is where the T-cells mature. __Leukocytes__ Leukocytes are the white blood cells of the innate immune system that identify and eliminate pathogens. __Lymph Nodes__ Lymph nodes are small bean shaped structures that produce and store cells that fight infections and diseases. They are part of the lymphatic system. __Bone Marrow__ Our bone marrow produces red blood cells, white blood cells and platelets. media type="custom" key="26170978" width="381" height="351" This video is a very simplified explanation of how the immune system reacts to a threatening pathogen. It also mentions a few key parts of the system that were not discussed above.
 * Components**
 * Final Overview**

[] <- "Our immune system can unmask tumours and cure cancer." [] <--- Top foods to boost your immune system [] < Boosting the immune system to fight cancer
 * Further Reading**

[] [] [] [] [] [] [] [] []
 * Sources**