Structure of Dna

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Running head: STRUCTURE OF DNA

Structure of DNA
University Of Phoenix
Principles of Biology
Phil Clifford
January 13, 2009

Structure of DNA
Since the beginning of human history, people have been intrigued how traits are inherited from one generation to the next. What is DNA? DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Most DNA is located in the cell nucleus (called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (mitochondrial DNA or mtDNA) (U.S. National Library of Medicine, January 12, 2009, p. 1). This paper will explain the structure of DNA, discuss how the structure of DNA allows it to serve as the basis for inheritance, examine how meiosis allows DNA to be divided into gametes, and describe how this relates to Gregory Mendel’s patterns of inheritance. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine. The sequence of nucleotides determines individual hereditary characteristics. The abbreviation stands for deoxyribonucleic acid, a double-stranded nucleic acid, in which the two strands twist together to form a helix. The strands consist of sugar and phosphate groups, the sugars being attached to a base — adenine, thymine, guanine, or cytosine. In DNA the bases pair to form a ladder-like structure, with adenine paired with thymine and guanine with cytosine. DNA forms the basis of inheritance in all organisms, except viruses, the DNA code being sufficient to build and control the organism. DNA is located in the nucleus of all cells; the substance of the chromosomes that separate out from the nucleus when cells divide, and it carries the genes, each of which is a segment of a DNA molecule. A small fraction of total DNA is present in mitochondria that codes for a few mitochondrial proteins. This DNA is...
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