H O Formation of a nucleotide Condensation water removed Hydrolysis water added A nucleotide is formed when phosphoric acid and a base are chemically bonded to a sugar molecule In both cases water is given off and they are therefore condensation reactions Double Stranded DNA The double helix structure of DNA is like a ladder twisted Into a corkscrew shape around its longitudinal axis It is unwound here to show the relationships between the bases The way the correct pairs of bases are attracted to each other to form hydrogen bonds is determined by the number of bonds they can form and the shape length of the beso The template strand the side of the DNA molecula that stores the information that is transcribed into mRNA The template strand is also called the entisense strand The other side often called the coding strand has the same nucleotide sequence as the mRNA except that T in DNA substitutes for U in mRNA The coding strand is also called the sense strand a Sugar deoxyribose b Phosphate c Hydrogen bonds between bases 2 a Explain the base pairing rule that applies in double stranded DNA Formation of a dinucleotide Two nucleotides are linked together by a condensation reaction between the phosphate of one hudentide and the sugar of another 1 The diagram above depicts a double stranded DNA molecule Label the following parts on the diagram d Purine bases e Pyrimidine bases b Explain how this differs in mRNA c Describe the purpose of the hydrogen bonds in double stranded DNA