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Home PART ONE |
THE BLUEPRINT OF LIFEIs the DNA string a computer program?
Most readers will be familiar with the term DNA. DNA is an abbreviation of deoxyribonucleic acid, DNA's real chemical name. For the readers without a background in organic chemistry , there are different groups of chemical groups in organic chemistry(the chemistry of carbon containing molecules) . In the DNA molecule the important groups are sugars ( there are many different types of sugars and the one we drink in tea is just one of many types) bases and phosphate groups. The way these different chemical structures bind with each other determine the genetic or DNA code. The sugar bind to a base and to phosphate group. The three groups are than called a nucleotide. Thousands or millions of nucleotides bind together to form the DNA molecule This structure was only discoverd fifty years ago (1953) and in 1962 Francis Crick , James Watson and Maurice Wilkins received the Physiology and Medicine Nobel price for this discovery. The name deoxyribonucleic acid (DNA) is derived from the sugar present in DNA. This sugar is called deoxyribose. DNA is a large complex molecule consisting of many nucleotides. It is also important to realize that DNA is a three dimensional structure. It is present in all living beings and in some viruses. It contains the code responsible for the development and the sustainment of life. This code is also known as the genetic code. The aim of this page is to explain this code in a simple manner and than to compare it to computer coding. We provide a list of sites discussing DNA in greater detail at the end of this page. It is very important to realize when looking at the genetic code, that all the molecules involved are three dimensional structures. The most important part of the DNA molecule consists of four chemical structures called the purine and pyrimidine bases. Their names are:
Adenine Guanine
The PYRIMIDINES Thymine Cytosine
There is also a third base known as Uracil (a pyrimidine ( it is also important but will be discussed later) For the purpose of this discussion the bases will be color coded.
red = thymine green = cytosine blue = guanine
The basic structure of the DNA consists of two parallel strings. The bases are attach to and protrude into space from these strings, as shown in the next drawing. Click on the image to enlarge the view. Try to imagine a three dimensional structure. 
The backbone of the parallel strings consists of phosphate groups and sugar groups. The sugar group in DNA is deoxyribose. ( if you are interested in more detailed descriptions of the DNA molecules refer to the links supplied at the end of this page) Now something very important. The purine bases attract pyrimidine bases and vice versa. In a very special and important way. The protruding tip of on base will attract the protruding tip of another base. BUT THERE IS AN IMPORTANT CONDITION. Adenine and thymine only attract each other and not cytosine or guanine. Cytosine and guanine behave in the same way. They only attract each other and not adenine and thymine. This is also known as base pairing. There two base pairs. The adenine-tymine base pair and the guanine -cytosine base pair. These base pairs are of the utmost importance and one of the foundations of the DNA code. Refer again to the previous drawing. HREF = "DNAview.html">Enlarged view These bases contain the DNA code and base pairing is responsible for replicating the DNA code.( More about this a little later.) The base pairs form multiple bonds that keep the two strings together as illustrated in the previous drawing. Just click for an Our color coding is used. 2.Red for thymine 3.Green for cytosine 4 Blue for guanine. It should be clear that if the strings separate , it will be possible for them to duplicate themselves. The DNA code is able to replicate itself. This happens indeed. When a cell divides each daughter cell gets a copy and each copy is an exact replica of the original DNA in the mother cell. The following drawing illustrate this replication. The strings separate and two copies are produced when this happens. Click on the drawing to enlarge it.
The DNA molecule is a three dimensional molecule and the two strings form a spiral structure, known as the double
helix.
RNA
Many of you will be familiar with the term RNA, an abbreviation of ribonucleic acid.
RNA is a molecule very similar to DNA. Like DNA it is present in all living beings and in some viruses
There are however a few differences between the two.
(I) RNA consists only of a single string.
(II) The pyrimidine bases are slightly different because uracil replaces thymine.
(III) The sugar deoxyribose is replaced by ribose ( another type of sugar).
(IV) There are several types of RNA .
a Messenger RNA abbreviated mRNA
b Transfer RNA abbreviated tRNA
c Ribosomal RNA.
These changes allow the RNA molecule to perform the function of protein synthesis, the corner stone
of life. In the color coding red (thymine ) is replaced by (depending on your browser and computer) by
pink or purple.
The next drawing illustrates the basic structure of a RNA molecule.
(Click on the image to enlarge the view.)
Messenger RNA (mRNA) is formed from the template provided by DNA. Parts of the DNA string separates and RNA is formed as shown in the next drawing. Click on the drawing to enlarge it. 
It illustrates the separation of the two DNA strings and how the one string acts as a template for the synthesis of mRNA. Once the RNA molecule is formed it moves away to other parts of the cell. Here it will provide the code for protein synthesis. This is illustrated in the next drawing. Click on the drawing to enlarge it.  It illustrates how the new mRNA string moves away from the DNA where it was formed.
PROTEIN
The bond between the different amino acids are known as peptide bond. The protein chains formed when amino acids bind with one another , is also known as polipetides. There are two major types of protein namely enzymes and structural proteins. Hair, horns, the epidermis of the skin, muscle etc. are examples of structural protein. They gives strength and form to structures. Enzymes are catalysts that induces chemical reactions. They won't invent new of reactions but will make it easier for an existing reaction to take place. It is very important to understand that each enzyme is only a catalyst for one specific chemical reaction and will not influence other chemical reactions. The following are an examples of a reactions catalyzed by a enzyme: Sucrose. Sucrose is the chemical name for the ordinary sugar we use every day. It actually consists of two smaller sugar molecules . Sucrose is a combination of fructose and glucose . To absorb sucrose in the digestive system the bond between fructose and glucose needs to be broken down and sucrose is split into two molecules This cleaving of sucrose is caused by an enzyme known as sucrase. The structural proteins are found in the bodies support systems giving support to the body . ( The exoskeleton in insects are also an example). other kinds of protein. Hemoglobin is an iron containing protein that transports oxygen in bloodstream and delivers it ( the oxygen ) to the tissues. A change in the DNA coding will effect the amino acid sequence in the protein molecule and lead to a protein that functions abnormally. There is a DNA code consisting of three bases for every amino acid . This code is transfer to RNA . The mRNA is large molecules having the code for one protein molecule. The body need to form a different mRNA for every protein it is going to manufacture. tRNA is a smaller RNA molecule and there is at least one type of tRNA for every amino acid. ( there is at least 20 different sRNA molecules and every one is specific for only one type of amino acid).
Chromosomes Humans (Homo sapiens have 23 pairs ( or 46 in total). One pair is every important and differs between males and females. This is the sex chromes. In women the pairs are identical and called X chromosomes. The X chromosome is a large chromosome. Men only have one X chromosome. The other partner in men is a tiny chromosome called the Y chromosome. We inherent 23 chromosomes ( one partner of each pair from our fathers and the other 23 from our mothers. The sperm that fertilized our mother's ovum ( egg cell) determined our sex. If you are a male the sperm coined a Y chromosome and if you are a female it was a sperm containing a X chromosome. Click on the following link to view a photo of human chromosomes. Human male karyotype (Denver-London method) The chromosome pairs form an important link in sexual reproduction. Our bodies develop (grow) and arid are maintained through cell a sexual reproduction of cells ( a process called mitosis) Cells divide producing growth or replacing damaged or or dying cells. The number of chromosomes remains constant during mitosis. Reproducing is however different. We only pass half ( one member of each pair) to our offspring. The other half is donated by our partner of the opposite sex. The male partner contributes 23 chromosomes , one being either a X or a Y chromosome. The female partner contributes the other 23 chromosomes and the sex chromosome she donates will always be a X. You can now view a few illustrations. We simplified it and uses a species with 4 pairs ( 8 chromosomes). The species has 6 autosomes ( non sexual chromosomes) and two sex chromosomes. The next drawings illustrates the chromosomes of a male member and a female member of our 8 chromosome species. Illustration of 8 chromosome species
The next drawing illustrates what happens after mitosis. Following mitosis there are two daughter cells each containing 8 chromosomes which are exact copies of the DNA of the mother cell. Chromosomes in daughter cells following mitosis The next set of drawings enplane the process of " Cross over". Before meiosis commences the different chromos pairs approach there partner and exchange chromosomal material. The resultant chromosomes differs from there predecessors.. But notice very little or no chromosomal material is exchanged between the large X and small Y chromosome. Cross over constantly change the the DNA molecules in the chromosomes over generations, The Y chromosome however is an exception. It is very small in comparison to the X chromosome and very little genetic exchange occurs between the to. The result is that the Y chromosomes stay nearly the same with passing generations ( change very little with passing generations). The Y chromosome in a male is nearly the same as the one that was present in his paternal great grand father. Click on the following link to view illustrations explaining cross over.
Chromosomal cross over during meiosis : A graphic explanation
One sperm contains 3 autosomes and a Y chromosome and the other sperm contains a X chromosome. Through the process
of meiosis the mother cell produces two daughter cells that are different . They contain only 4 instead of 8 chromosomes and
one cell is a female and the other a male cell. Notice also the effects of crossover. The genetic material
in each daughter differs from their partner. This is way siblings ( except identical twins) are not exact
replicas of each other . If genetic were not exchanges during meiosis , this would have been the case in siblings of the
same sex and the only differences between brothers and sisters would be the Y chromosome.
The next section will illustrate how the DNA code controls life.
A schematic presentation of this whole process is available
HERE!
The first step is the formation of mRNA. (as discussed earlier)
tRNA binds or pick up amino acids. Each tRNA is specific for only one kind of amino acid and will
only pick up this specific amino acid.
The mRNA attach itself to a cell structure known as a ribosome. tRNA can only bind with specific areas
on the mRNA . This binding occurs according to the "three base code". Three bases on tRNA molecule
will attach themselves to the corresponding base pairs on the mRNA molecule. These three bases are
specific for a specific amino acid.
Click here for a more graphic
explanation of protein synthesis.
The sequence in which tRNA lines up on mRNA is determine by the genetic code. The sequence of the tRNA
molecules in turn determine the sequence of the amino acids in the protein molecule and thus determine
the structure of the protein.
Most of the proteins formed are enzymes and as already discussed enzymes will enhance a specific
chemical reaction. The sum of all the chemical reactions occuring in a living being is
responsible for life and all these reactions are controlled by enzymes.
The final step in the DNA software code is thus the chemical reactions catalyzed by the enzymes.
The product of the final step is life. In biology these reactions are known as metabolism.
A very important fact to remember is that every cell in a specific individual contains absolute
the same genetic code. The code in the embryo cells ( stem cells) and in a highly specialized nerve cell
are exactly the same, only different parts of the DNA molecule are activated to produce RNA as the cell
gets older and specializes . ( nerve cells are different from liver cells , but exactly the same DNA code
produces both).
It is important to remember that we have two double helix DNA molecules coding for the same enzymes or the same
genetic trait. Lets take the color of our eyes. ( The following is just a crude over simplified way to
explain a basic genetic principle). There are two enzymes producing different proteins in the eye. The one protein will
reflect blue light. The individual with this trait will have blue eyes. The other protein catalyses the the production of a
protein that reflects less light and only the lower frequency spectrum. Thus person will have brown eyes.
If both parents have
blue eyes , there children will have blue eyes. Both sets of DNA will code for blue eyes.
BUT if one parent has blue eyes and the other brown eyes there children would have brown eyes. Although the
one set of DNA will code for blue eyes, the protein reflecting brown eyes will neutralizes the
blue reflecting protein and their children will have brown eyes. We state again this example in a over
simplification. It is used to illustrate how inheritance work and has no direct connection to the inheritance
of eye color.
The heading of this page is "Is the DNA string a computer program? " A computer program is a set
of instructions controlling the functions of the computer and the hardware attach to it. The code reside in the ROM
(read only memory) and on the hard disk and is activated when the computer starts. This code than forces the computer
perform certain actions just as the DNA leads to protein synthesis and enzymes that forces the cell to perform
certain actions. The DNA
code is thus also a set of instructions controlling the functions of a cell and its relation with
it's sisters cells. The more advanced the organism the more important is this relationship with
it's sisters cells. This relationship with its sister cells leads to one important difference
between a computer program and the DNA code. The code contained in The DNA molecule is a program that is able to build
its own hardware.
This ability to build or construct its own hardware is the only major difference between DNA and and a computer program.
It is universally accepted that outside influences ( most importantly ionizing radiation) change the DNA structure
that lead to the production of new genes . New genes lead to new proteins and enzyme . Viruses attaching themselves
to the DNA molecule are also responsible for genetic changes. Alteration in the sequence of the purine bases are
could mutations. Modern biological science universally accepts that these randomly coincidental mutations are
responsible for the development of all live ( evolution).
We all heard about mutations. What is it. A mutation happens when the DNA code is altered. Anything that
alters the sequence of the purine bases will alter the code. Altered code will at the very least produce a slightly
altered protein or at its worse no protein at all. It is obvious that most mutations will have serious
effects. Any alteration in a protein structure effect its function. So most mutation are bad.
It is also believed that some mutations might introduce new genes that will enhance or be to the advantage
of the organism under certain circumstances. These are a good mutations.
Mutations occurring in the sexual organs ( testis and ovaries ) will be transmitted to the organisms offspring.
Another important point is that mutations are random events and each gene has an equal change of being effected.
THIS IS A VERY IMPORTANT.
How many times had you to reload computer programs ? Power failures etc. do influence the electromagnetic storage
systems of computers. Are these disturbances not comparable to mutations?
Visit the following page to compare the DNA code and the binary code used in computers and microchips.
Go here.
If you want to know more about basic computer programming
GO HERE.
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