3B1+Wei+Ren+Bio+Essay(DNA)

Deoxyribonucleic acid (DNA), is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus and almost every cell in our body has the same identical DNA. The information in the DNA is coded into four chemical bases, Adenine (A), Guanine (G), Cytosine(C), and thymine (T). The sequence of these bases would determine the information available for building and maintaining an organism, as like how the alphabets form words. These DNA form base pair, with A pairing with T and G pairing with C. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.  Scientist use the term "double helix" to describe DNA's winding, two-stranded chemical structure. This shape gives DNA the power to pass along biological instructions with great precision. Each "rung" of the ladder is made up of two nitrogen bases, paired together by hydrogen bonds. Due to its specific base pairing system if you know the sequence of the bases on one strand of a DNA double helix, it is simple to figure out the sequence on the other strand. DNA's unique structure enables the molecule to copy itself during cell division. When a cell prepares to divide, the DNA helix splits down the middle and becomes two single strands. These single strands serve as templates for building two new, double-stranded DNA molecules -a replica. In this process, an A base is added wherever there is a T, a C where there is a G In addition, when proteins are being made, the double helix unwinds to allow a single strand of DNA to serve as a template. This template strand is then transcribed into mRNA, which is a molecule that conveys vital instructions to the cell's protein-making machinery. [] [] [] [] [] http://publications.nigms.nih.gov/thenewgenetics/chapter1.html#c1