Understanding Elements of DNA

2235 Words Oct 22nd, 1999 9 Pages
DNA REPLICATION WHAT IS DNA? DNA is a molecule that has a repeating chain of identical five-carbon sugars (polymers) linked together from head to tail. It is composed of four ring shaped organic bases (nucleotides) which are Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). It has a double helix shape and contains the sugar component deoxyribose. THE PROCESS OF DNA REPLICATION How DNA replicates is quite a simple process. First, a DNA molecule is "unzipped". In other words, it splits into two strands of DNA at one end of the DNA molecule. This separation will cause a formation of a replication fork. After the replication fork has been established the strands of DNA are ready for the next stage. On each strand is a …show more content…
THE FIRST MODEL OF A DNA MOLECULE Two scientists from Cambridge University named James Watson and Francis Crick were the first ones to actually build the actual structure of the DNA molecule. In building their DNA molecule, they discovered that there were two different types of bases, purines and pyrimidines. Purines were the larger of the two types of bases, and are the double ringed structures [example of nucleotides that fit in this category are adenine (A) and guanine (G)]. Pyrimidines were the smaller of the two types of bases, and are the only single ringed structures [example of nucleotides that fit in this category are cytosine (C) and thymine (T)]. The two scientists also discovered that in the DNA molecule, only two base pairings of nucleotides are possible, adenine (A) with guanine (G) and thymine (T) with cytosine (C). This is because of the improper forming of hydrogen bonds. In a G-C pairing, three hydrogen bonds are formed whereas in an A-T pairing, only two hydrogen bonds are formed. The Watson-Crick model also suggested that the basis for copying the genetic information is complementary. For example, if the sequence for one chain of DNA is ATTGCAT, then the sequence of its copy, or complementary side would be TAACGTA. Hence, to copy a DNA molecule you would only need to unzip its structure and
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