Biology OCR Module 2 Section 3:
Nucleotides and Nucleic Acids
Questions & Answers
Structure of DNA - ANSWERSFormed of nucleotides - deoxyribose sugar, phosphate
molecule, nitrogenous bases (adenine, thymine, guanine, cytosine)
Purines - ANSWERSAdenine and Guanine - contain double ring structure
Pyrimidines - ANSWERSCytosine and Thymine - contain single ring structures
Sugar-phosphate backbone - ANSWERSAlternating molecules of sugar and phosphate
that anchor the nucleotides in a strand of DNA or RNA.
Run anti-parallel from 5' to 3', and 3' to 5'
Held together by phosphodiester bonds
Forms double helix
Adenine and thymine - ANSWERSComplementary - held together with 2 bonds
Cytosine and guanine - ANSWERSComplementary - held together with 3 hydrogen
bonds
Nitrogenous bases - ANSWERSAdenine, Thymine, Cytosine, Guanine
Information content of DNA
Pattern of bases controls sequences of amino acids - read in triplet codons for protein
synthesis
What is DNA code? - ANSWERSNon-overlapping - each base is part of one codon
Universal - codes for all proteins and is present in all living things
Degenerate - more than one codon codes for the same amino acid
Mutations of DNA - ANSWERSSubstitution, addition, or deletion of nitrogenous bases -
may change tertiary structure or quaternary structure
Nucleotides and Nucleic Acids
Questions & Answers
Structure of DNA - ANSWERSFormed of nucleotides - deoxyribose sugar, phosphate
molecule, nitrogenous bases (adenine, thymine, guanine, cytosine)
Purines - ANSWERSAdenine and Guanine - contain double ring structure
Pyrimidines - ANSWERSCytosine and Thymine - contain single ring structures
Sugar-phosphate backbone - ANSWERSAlternating molecules of sugar and phosphate
that anchor the nucleotides in a strand of DNA or RNA.
Run anti-parallel from 5' to 3', and 3' to 5'
Held together by phosphodiester bonds
Forms double helix
Adenine and thymine - ANSWERSComplementary - held together with 2 bonds
Cytosine and guanine - ANSWERSComplementary - held together with 3 hydrogen
bonds
Nitrogenous bases - ANSWERSAdenine, Thymine, Cytosine, Guanine
Information content of DNA
Pattern of bases controls sequences of amino acids - read in triplet codons for protein
synthesis
What is DNA code? - ANSWERSNon-overlapping - each base is part of one codon
Universal - codes for all proteins and is present in all living things
Degenerate - more than one codon codes for the same amino acid
Mutations of DNA - ANSWERSSubstitution, addition, or deletion of nitrogenous bases -
may change tertiary structure or quaternary structure
