3G2+Bio+Essay+By+Delvin,+Zhixian,+Brion+and+Canxiang

Members: Delvin Zhixian Brion Canxiang (Please Note: There is NO colour coding as all four of us stayed back in school to do it together, instead of splitting up the workload and leaving every member to upload at their own pace. We felt that this would be more effective as this further ensures that the whole essay is a joint effort

__**Components of DNA**__

Firstly, DNA is one of the classes of nucleic acid. Being a basic building block of life, it has two functions: to replicate genetic cells and for protein synthesis. Basically, the DNA is a molecule of heredity that contains a long double-helix chain of nucleotides (often thousands of nucleotides long), each made up of a deoxyribose molecule joined to a phosphate (-PO3) and an organic base.

One of the key components of DNA would be sugar, otherwise known as deoxyribose. Simply put, the deoxy-prefix means that the sugar has a deficit of oxygen. Another vital component is the nitrogenous bases, categorized into phosphates, pyrimidines and purines. When phosphates merge with a nucleotide, it becomes polymerized to form DNA. Nucleotides comprise 3 phosphates are precursors of DNA. Purines primarily compose of carbon and nitrogen rings. Both purines- Adenine and Guanine can be found in DNA and RNA (another type of nucleotide). There are two broader types of nitrogen bases, the one-ring pyrimidines and two-ring purines.

There are 4 bases of nucleic acid in DNA, namely, Adenine, Thymine, Guanine and Cytosine. Adenine and Thymine complement each other (as they both only form 2 hydrogen bonds), which means that they are always paired to each other, while the same applies to Guanine and Cytosine (which forms 3 hydrogen bonds). (Simplified diagram)



Each spiral strand contains a sugar phosphate “backbone”, and attached bases, and is connected to a complementary strand through hydrogen bonding between paired bases, which consist of adenine with thymine, and guanine with cytosine.

The double-stranded helix structure of the DNA forms as a result of interactions between the adjacent base pairs. This interaction consists of Van der Waals attractions and this force causes the base pairs to come together so that they are in close contact. The result is a stack of base pairs, one on top of the other, with hardly any space between them. These interactions are known as stacking interactions, and they are the main force that holds the two strands together in a double helical form.




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Bibliography & Resources: [] [|http://www.massey.ac.nz/~wwbioch/DNA/DNAmake/framset.htm] [] [] [] [] [] GCE "O" Level BIOLOGY Matters, Published by Marshall Cavendish Education