Structure and Roles of Nucleic Acids
MODULE 2: GENETICS, VARIATION AND NATURAL SELECTION
SPECIFIC OBJECTIVES & EXPLANATORY NOTES
1. Structure and Roles of Nucleic Acids
1.1 illustrate the structure of RNA and
DNA using simple labelled diagrams; The genetic substance found in all organisms called DNA or deoxyribonucleic acid is a kind of nucleic acid.
Nucleic acids consist of two long polymers of simpler units, called nucleotides; that are composed of three (3) main units as shown below: 1) A pentose sugar (deoxyribose in DNA, ribose in RNA) 2) A nitrogenous base (a purine or pyrimidine) 3) A phosphate group
These nucleotide monomers link via phosphodiester bonds and form long chain polynucleotide chains.
Basic structure of a polynucleotide:
These polynucleotide chains can bond together via the nitrogenous bases on their molecules. There are two main classes of nitrogenous bases found on nucleotide molecules: * The purines which consist of the bases: adenine (A) and guanine (G)
* The pyrimidines which consist of the bases: cytosine (C) and thymine (T) These bases form bonds with only one other type of base, particularly A-T or C-G parings. This is known as complementary base pairing.
These bases are held together via weak hydrogen bonds that stabilize DNA molecules.
Thus these linkages between polynucleotide chains form the double stranded structure of DNA.
In contrast, the substance called RNA or ribonucleic acid is another type of nucleic acid. It differs from DNA structurally as it is: * a single stranded molecule * contains the pentose sugar ribose * the pyrimidine base uracil replaces the thymine base of DNA.
1.2 explain the importance of hydrogen bonds and base pairing in DNA replication;
In DNA molecules, the double helix structure is held together by hydrogen bonds between complementary base pairs. In order for bases to orient themselves in this way, one DNA strand will run in a 5’to 3’
SPECIFIC OBJECTIVES & EXPLANATORY NOTES
1. Structure and Roles of Nucleic Acids
1.1 illustrate the structure of RNA and
DNA using simple labelled diagrams; The genetic substance found in all organisms called DNA or deoxyribonucleic acid is a kind of nucleic acid.
Nucleic acids consist of two long polymers of simpler units, called nucleotides; that are composed of three (3) main units as shown below: 1) A pentose sugar (deoxyribose in DNA, ribose in RNA) 2) A nitrogenous base (a purine or pyrimidine) 3) A phosphate group
These nucleotide monomers link via phosphodiester bonds and form long chain polynucleotide chains.
Basic structure of a polynucleotide:
These polynucleotide chains can bond together via the nitrogenous bases on their molecules. There are two main classes of nitrogenous bases found on nucleotide molecules: * The purines which consist of the bases: adenine (A) and guanine (G)
* The pyrimidines which consist of the bases: cytosine (C) and thymine (T) These bases form bonds with only one other type of base, particularly A-T or C-G parings. This is known as complementary base pairing.
These bases are held together via weak hydrogen bonds that stabilize DNA molecules.
Thus these linkages between polynucleotide chains form the double stranded structure of DNA.
In contrast, the substance called RNA or ribonucleic acid is another type of nucleic acid. It differs from DNA structurally as it is: * a single stranded molecule * contains the pentose sugar ribose * the pyrimidine base uracil replaces the thymine base of DNA.
1.2 explain the importance of hydrogen bonds and base pairing in DNA replication;
In DNA molecules, the double helix structure is held together by hydrogen bonds between complementary base pairs. In order for bases to orient themselves in this way, one DNA strand will run in a 5’to 3’