Understanding A DNA SequenceThere are four types of nucleotides in DNA. Each nucleotide is assigned a letter in a DNA sequence; A (Adenine), C (Cytosine), G (Guanine), and T (Thymidine). Each strand of DNA is a sequence of these four nucleotides. One strand might be AACGGCTTA. The second strand on the DNA sequence is the exact opposite of the first strand, always using the complimentary nucleotides, A with T and C with G. So the exact opposite of the DNA sequence already given would be TTGCCGAAT. This is a very short strand just for use as an example. When scientists test DNA they will use tiny fragments of a DNA sequence as long as 1,000 base pair of nucleotides and download the DNA sequence into a computer program for testing. As a strand, this sequence would look like this:
A T A T C G G C G C C G T A T A A T
Every time a cell multiplies, the DNA sequence has to make exact copies of itself. This happens with the help of enzymes called DNA polymerase. What will happen is the two parts of the double strand of the DNA sequence will split, and then an exact copy of that half of the double strand will be made. For example:
This resequencing of the DNA sequence will happen about three billion times every time a cell splits, and the strands of one DNA sequence are extremely long. In the largest human chromosome (where the DNA sequences are stored), each strand is about 220 million base pairs long.
Rarely DNA will not match up just right and when this happens it can damage a cell and cause specific diseases and ailments. In recent news, a study from a MA hospital found that a certain nucleotide deletion can be a cause for schizophrenia in humans. While it is not the only cause, other scientists are really taking stock in this information and conducting their own in depth studies on this type of DNA sequence deletion.
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