University of Phoenix
BIO/240 - GENERAL BIOLOGY
Deoxyribonucleic acid or DNA is found in basically all organisms including humans. It is the hereditary material that basically every person has and is found in both the cell nucleus and the mitochondria. Most of a person’s DNA is nuclear DNA because it is found in the nucleus; small portions of DNA can also be found in the mitochondria, giving this type the name mtDNA or mitochondrial DNA. DNA has many properties; one of its most important is that it ...view middle of the document...
A, C, G and T are all found in DNA, while A, C, G and U are found in RNA. Once the double helix structure is finished, it appears to look much like a twisting ladder where the base pairs are the steps and the phosphate and sugar molecules are the vertical sides of the ladder. The structures of DNA and nucleotides are pictured below:
Due to the complexity and involvement of the entire DNA structure, each part of it needs to be looked at in depth. A nucleotide is made up of a nucleobase or nitrogen base, a five-carbon sugar of either ribose or 2’-deoxyribose, and between one and three phosphate groups. When the nucleobase and sugar are brought together, they make up a nucleoside. Two, three, or most commonly, 5 carbon bonds are also produced from the bonding of phosphate groups and sugar. When the phosphate group binds to two of the sugar’s hydroxyl groups, cyclic nucleotides form. Where the sugar is ribose, ribonucleotides occur and when deoxyribose contains the sugart, deoxyribonucleotides arise. In addition to all of this, nucleotides can also contain either a purine or pyrimidine base. In DNA, guanine and adenine are purine bases that contain a pair of fused rings, while cytosine and thymine are pyrimidines. In RNA, uracil is used in the place of thymine. The polymeric macromolecules that are produced from nucleotide monomers are nucleic acids. The first picture below shows the most common nucleotides structural elements while the second shows a close up of the chemi.cal structures of DNA and RNA bases.
DNA’s ability to replicate itself is one of the most crucial functions that it performs. In fact, DNA replication is the most fundamental occurrence in all living organisms in order to copy their DNA and result in biological inheritance. This relationship between the double helix and genetic replication was easily and quickly discovered by Watson and Crick. During this process, each strand the DNA molecule is used as a model for the recreation of the corresponding strand. As a result of DNA replication, two like DNA molecules are able to be formed from a single double-stranded DNA molecule that are checked for fidelity via cellular error toe-checking and proofreading mechanisms. DNA replication occurs at specific locations in the genome of the cell called “origins”. A replication fork can be formed from the unwinding of DNA at the origin and the synthesis of new strands. By having the enzyme that synthesizes the new DNA by adding nucleotides that are matched to the original strand in addition to DNA polymerase, there are a several other proteins that are also associated with the fork and aid in the start and persistence of DNA synthesis. DNA is also able to replicate outside of a cell; this is called in vitro. When this occurs, DNA polymerases that are separate from the cell as well as artificial DNA primers begin DNA synthesis at known sequences in a template molecule. A specific target DNA fragment can be amplified from a pool of...