DNA strands are composed of nucleotides which serve as building blocks of DNA and RNA. Each of these nucleotides contains a phosphate which is attached to a deoxyribose sugar, and one of the four bases which include: guanine, cytosine, adenine, and thymine. The base pairing is very important, because they can only pair a certain way. The nitrogen base guanine only pairs with cytosine, and the nitrogen base adenine only pairs with thymine. These base pairs are held together by hydrogen bonds. The nucleotides are arranged into a spiraled helix forming into what is known as DNA. It is very important for the nitrogen base structures to be paired correctly, because these nucleotides are what carry the genetic information in order to form a sequence of amino acids which leads to the creation of a protein strand. A single change in the nucleotide can cause a difference within DNA and can cause a change in the amino sequence of a protein. This is most commonly known as a mutation. A mutation is a failure to store genetic information correctly or faithfully. The way nitrogen bases are sequenced varies in different types of organisms. It turns out that different species of organisms have different proportions of bases in their DNA. This is what distinguishes each organism as different from each other. The only reason why humans aren't bananas is because humans have a different number of proportions in their bases than bananas or anything else. For example, one species might have DNA that has 30% Adenine, 20% Cytosine, 20% Guanine and 30% Thymine, while on the other hand a different species could have 20% Adenine, 30% cytosine, 30% guanine, and 20% thymine. Despite having different proportions all of the percentages of the bases equal to 100% and that is true for every organism. The nitrogen base sequence for a human is 30.9 % Adenine, 29. 4% Thymine, 19.9% Guanine, and 19.8% Cytosine. This sequencing is very important because if this wasn't the exact numbers as shown as above, then you wouldn't get a human, but instead you would get some other form of life. The smallest change in percentage can change the whole organism. For example, the base percentages of a chicken and grasshopper are almost similar, but they are still two different organisms. The base percentages for a chicken are 28.8% Adenine, 29.2% Thymine, 20.5% Guanine, and 21.5% Cytosine. The base percentages for a grasshopper are 29.9& Adenine, 29.3% Thymine, 20.5% Guanine, and 20.7% Cytosine. Even though these two organisms have almost similar percentages and the same amount of guanine, just those small changes in numbers distinguish what the organism will be. The proportions in the bases are what make a human a human rather than a bacteria or yeast. The proportions of yeast are 31.3% Adenine, 32.9% Thymine, 17.7% Guanine, and 17.1% Cytosine. If the nitrogen bases had these proportions in their bases than most likely you will end up with yeast, because these proportions are mainly for yeast, and only yeast. The proportions of E. coli are 24.7% Adenine, 23.6% Thymine, 26% Guanine, and 25.7% Cytosine. Because of these differences in proportions, it is impossible to be bacteria with the proportions of a human. The Nitrogen bases in the DNA play a very big role in determining species. Therefore it is necessary for the sequencing to be right, so yeast can be yeast, and human can be a human.
-By Kharishma Patel, Deepthy Varghese, Jeswina John, and Miranda Juergens
8th period, Medical Microbiology, Rickard
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