3.3.2 State the names of four bases in DNA.
(Eggling 1)
3.3.3 Outline how DNA nucleotides are linked together by covalent bonds into a single strand.
A nucleotide is a combination of a phosphate, a sugar, and a base. They are made up of the four bases stated in 3.3.2. Adenine and guanine are called purines and are made up of two carbon rings (Bowen 1). Cytosine and Thymine are called pyrimidines are consist of a single carbon ring (Bowen 1). The reason for this classification is because in nucleic acids, base pairs are always formed between a purine and a pyrimidine (Eggling 1). Adenine and Thymine form two bonds between each other while guanine and cytosine form three bonds between each other. According to the base pair rule, the opposite complementary bases attract to one another which is why DNA nucleotides can be linked together into a single strand (Bowen 1).
3.3.4 Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds.
Complementary base pairing is the bonding between the base pairs Adenine-Thymine and between Guanine-Cytosine. Hydrogen bonds are what make up the bonds between the two bases (May 1). Like stated in 3.3.3 A-T consists of two bonds between each other and G-C consists of 3 (Ophardt 1). The reason for the twist in the ladder shaped formation is because the complementary bases are pulling inwards in order to bring the bonds closer together. Thus a double helix shape is formed from using complementary bases.
Works Cited
Bowen, R. A. "The Structure of Nucleic Acids." The Structure of Nucleic Acids. 29 Dec. 2001. Colorado State University. 24 Nov. 2008 <http://arbl.cvmbs.colostate.edu/hbooks/genetics/biotech/basics/nastruct.html>.
Eggling, Sue. "Nucleotide Structure." Nucleotide Structure. 2003. Clackamas Community College. 24 Nov. 2008 <http://dl.clackamas.edu/ch106-09/nucleoti.htm>.
May, Paul. "DNA." DNA. 1996. University of Bristol. 24 Nov. 2008 <http://www.chm.bris.ac.uk/motm/dna/dna.htm>.
Ophardt, Charles E. "DNA - Double Helix." DNA - Double Helix. Elmhurst College. 24 Nov. 2008 <http://www.elmhurst.edu/~chm/vchembook/582dnadoublehelix.html>.
