Bio 101 Dna Structure

Deoxyribosenucleic acid (DNA) encodes all the information required for life to exist. It is the genetic material that dictates many functions of a cell. DNA is heritable, meaning it is passed on from parents to offspring allowing many traits of a species to be passed on. Gregor Mendel, the Father of Genetics, described his experiments with pea plants in 1900 he identified a heritable trait, we now know to be the gene. Mendel found that the parental generation of pea plants could pass on traits, such as flower color and pod size, to offspring. He identified the ratios of inheritance, allowing him to determine that each parent contributed half of the genetic traits to the offspring. It was this finding that helped scientists to realize that there was some type of code that could be passed on to the offspring. Although the existence of something like DNA was hypothesized about for many years, the current model of its structure is mostly attributed to the work of Watson and Crick in 1953 (National Institute of General Medical Sciences [NIGMS], 2006).

Watson and Crick’s model identified DNA as a double-helix structure with two strands of repeating nucleotides. Nucleotides are molecules made up of a base, a phosphate group, and a sugar group (deoxyribose in DNA). There are four different nucleotides that make up DNA; guanine (G), adenine (A), thymidine (T), and cytosine (C; NIGMS, 2006). The two strands of DNA are joined to each other through each nucleotide’s base group, which creates a bridge. The resulting structure resembles a twisted ladder, the base groups forming the rungs and the phosphate groups of the nucleotides forming the sides through a phosphodiester bond (Castells-Brooke, 2001). However, each nucleotide can only pair up with one other nucleotide depending on the base it contains; A to T and G to C. Therefore, each strand is said to be a complement of the other strand (USNLM, 2009; Castells-Brooke, 2001). The base of each nucleotide is either a purine...