DNA Structure
... the atoms of the purine and pyrmidine rings. The hydroxyl groups on the 5'- and 3'- carbons link to the phosphate groups to form the DNA backbone. “A nucleotide is a nucleoside with one or more phosphate groups covalently attached to the 3'- and/or 5'-hydroxyl groups.” DNA is a double stranded macromolecule. “The two chains of the DNA double helix run opposite to each other. This head-to-tail arrangement is called antiparapllelism.” On chain ends in the 3’carbon and the opposite chain ends in the 5’carbon. Before a cell can divide, it must replicate its DNA. There are four major steps in DNA replication:1. DNA replication begins with one double strand of DNA. 2. Parental strand unwind and separate at several points along the DNA molecule, forming replication forks. 3. Each parental strand provides a template that attracts and binds complementary bases, A with T and G with C. 4. Sugar-phosphate backbone of daughter strands closed. Each new DNA molecule consists of one parental and one daughter strand, as a result of semiconservative replication. There are five types of enzymes involved in DNA replication: helicase, binding proteins, primase, DNA polymerase and ligase. DNA replication begins when a helicase breaks the hydrogen bonds that connect a base pair(occurs ...