Friday, March 15, 2013

CH5: The Power and The archives 2/2



Genetic Information in Our Body

Why Do We Read Genetic Information?

          There are generally two purposes to read from a memory: Copying and taking actions. When multiplying, the original cell copies its DNA to the descendent. Taking action is the process of ‘DNA translation’, where our body reads (i.e., translates) information stored in DNA in order to create a particular type of protein. 

 Forming  Protein

          To translate DNA to protein cell, first, DNA must be translated to RNA. Our body then follows the RNA instruction to create polypeptide (a.k.a., protein or poly amino acid). Again, DNA is NOT transformed into protein. Instead, it contains the instruction of how amino acids should be assembled and from a specific kind of protein. That’s why the process is called ‘DNA translation’, not ‘DNA transformation’.


Protein and Amino Acid

          Amino acid is a biologically organic compound consisting of carbon, hydrogen, oxygen, and nitrogen. There are about 500 known amino acids, each having different construction of the four basic elements--‘A’, ‘T’, ‘G’, and ‘C’. Out of these 500, only 20 amino acids are in living cells. A protein is a chain of one of these amino acids. After the formation, the chain coils up to a knot. The shape of a knot is uniquely determined by the sequence of amino acids. Therefore, the protein is also referred to as poly amino acid. 
       The sequence of amino acids, and thus the protein shapes, is determined by a three-letter symbol called a‘genetic code’ in DNA. Again, each letter in DNA can be either ‘A’, ‘T’, ‘G’, or ‘C’.  So there are 4 x 4 x 4 = 64 possibilities for a given symbol. It is this symbol which governs how a certain amino acid is formed. But, again, there are only 20 possible amino acid in living cells. So the translation from a genetic code to protein shapes (i.e., amino acid) is many-to-one translation. 


Enzyme and Cells

There is a special type of protein molecules called ‘enzyme’. Enzyme is a machine which creates a particular type of chemical products. This product gives a cell its individual shape and behavior. Since DNA determines the sequence of amino acid, it determines the type of enzyme and therefore the shape and behavior of cells. 


Same DNA,Different Functionalities

Every cell in our body contains the same DNA. But why does each cell act differently? For example, why does liver cells differ from kidney cells? The reason is that not all cells read DNA in the same way. When  DNA are read differently, the resulting protein shape is different and the cell is different.
If we trace back one step, we might ask ‘Why does cell read DNA differently?’ The answer is that the way DNA is read depends on the chemicals in the cell. Since the chemical level in a certain cell are not uniform, when the cell splits, each daughter cells would have different chemicals. So, they read DNA in a different way and so. This final result of DNA is visible in, for example, eye color, hair thickness, and so on. 
genetic information and natural selection

Vertical and Horizontal Transmissions

      DNA can be transmitted vertically or horizontally. Vertical transmission is a REPRODUCTION process. It is an act of copying DNA from one generation to the next, without any change. It is like copying a book from an archive. This is why we sometimes call DNA already in place ‘archival DNA.’ We call the path where the DNA is passed on, from our ancestors to our children, a ‘germ line’.
      Horizontal transmission is when DNA influence a creating of a cell via RNA. It is the process of DEVELOPMENT.

Reproduction

      DNA coils up into a ‘chromosome.’ Each human cell has 46 chromosomes, with the exception of reproduction cells. All regular cells are identical in addressing and contents. Reproductive cells (e.g., sperms and eggs) randomly took 23 contents from all 46 we have. When sperms mates with eggs, two 0f 23 chromosomes combine into 46 chromosomes in an embryonic cell. This cell multiplies, and the 46 chromosomes we inherited from our parent are copied to the new multiplied cells. 

Vying to Exist

Rival DNA and Natural Selection

      Natural selection is about how ‘rival DNA’--A particular content which shall replace the current content in a particular address--gets itself vertically transmitted into archival DNA. The vertical transmission depends on how well the DNA is transmitted horizontally to take action which fosters the ability to survive.


Durability and Generatability

      Things exists because it has ability to survive. This ability consists of durability and generatability. Durability is an ability to withstand the environment, at least long enough until generatability kicks in. Generatability is an ability to reproduce itself. DNA has poor durability but great generatability. The contents it stores constantly fade,  and must be regularly refreshed by the hosting organism.  Durability and generatabiity complement each other to preserve DNA information for millions of years. 

Mutation and Natural Selection

      Mutation is in fact to only way to evolve. If DNA did not make any error in copying, we would ALWAYS be the same. We would not be better nor worse in surviving. The the fastest we can evolve is therefore no greater than the rate of mutation. Natural selection, on the other hand, slows down the rate of evolution, because it throws away any mutation that degrades the ability to survive. 


Properties for Existence

      Anything that exists needs to have three properties
  1. The ability to self-replicate (hence, the thing is called a ‘replicator’): This is an ability to copy/populate itself. A replicator use instructions stored in a template to create a replica from raw material. 
  2. Random error in copying:  Error is essential for evolution. With our random error, the replicator would remain unchanged. It wouldn’t be able to adapt to changing environment. 
  3. Ability to exert power over their own future: Each property of a replicator should have different probability of being replicated. A replicator should be able to keep good properties and throw away bad properties. 


The Blind Watchmaker

The above three properties for existence are not attributed to a particular organism. They are general condition for any natural things. The natural selection is blind. It is the blind watchmaker.
“It is all utterly simple and automatic. It is so predictable as to be almost inevitable.”
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Book or Audiobooks?

Personally, I prefer audiobooks. It's fun, and I can listen when I'm doing something else. It also makes other activities (e.g., jogging) a lot more fun. For more detail about audiobooks, please read [this post].

There is one more reason that may encourage you to go for the audiobook version. You can get it now for FREE. Audible offers you a free trial for 14 days. Even if you get the book and cancel the subscription right away (so that you don't have to pay), you can keep the book. And, don't worry if you lost the audiobook file. Just log into audible.com. You can keep downloading the over and over again.
About the summary: It takes time to finish up a book. And, when you do, sometimes, you want to review what you learn from the book. If you do not make  notes as you read, you might have to go through the book once again. This can be time-consuming when you are dealing with a book. But you can still flip through the book and locate what you are looking for.

However, when the material is an audiobook, it is extremely hard to locate a specific part of content. Most likely you will have to listen to the entire audiobook once again.

This book summary will help solve the pain of having to go through the book all over again.

I am leaving out the details of the books. Most books have interesting examples and case studies, not included here. Reading the original book would be much more entertaining and enlightening. If you like the summary, you may want to get the original from the source below.

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