3.3.1 Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate.
A nucleotide is made of the sugar deoxyribose, a base (which can be either adenine, guanine, cytosine or thymine) and a phosphate group. Below is a representation of a nucleotide.
3.3.2 State the names of the four bases in DNA.
Adenine, Guanine, Cytosine and Thymine.
3.3.3 Outline how DNA nucleotides are linked together by covalent bonds into a single strand.
Below is a diagram showing how nucleotides are linked to one another to form a strand. A covalent bond forms between the sugar of one nucleotide and the phosphate group of another nucleotide.
3.3.4 Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds.
DNA is made up of two nucleotide strands. The nucleotides are connected together by covalent bonds within each strand. The sugar of one nucleotide forms a covalent bond with the phosphate group of another. The two strands themselves are connected by hydrogen bonds. The hydrogen bonds are found between the bases of the two strands of nucleotides. Adenine forms hydrogen bonds with thymine whereas guanine forms hydrogen bonds with cytosine. This is called complementary base pairing. Below is a digram showing the molecular structure and bonds within DNA.