dna three - structure & how it codes

• DNA

  Two strands wrapped around each other in a double helix
• Structure of DNA

  1. Nucleotides

  2. Complementary base pairing

  3. Gene coding for a protein
• Nucleotide

  Monomer unit of DNA, made up of a phosphate, sugar, and base
• Bases in DNA

  • Adenine
  • Thymine
  • Cytosine
  • Guanine
• DNA


  • Polymer made up of many nucleotides
  • Sugar phosphate backbone
  • Bases hold the two strands together through complementary base pairing
• Complementary bases


  A pairs with T, C pairs with G
• Determining complementary DNA strand

  Look at sequence of one strand and determine complementary bases for other strand
• Genetic code


  Sequence of DNA bases
• Gene


  Particular sequence of bases that codes for a protein
• Protein formation from DNA

  1. DNA sequence read as triplet codes

  2. Amino acids coded for by triplets combined in order

  3. Chain of amino acids folds to form protein
• Proteins


  • Unique shape allows them to carry out specific functions
  • Main uses are in enzymes, hormones, and structural proteins
• What are the monomers of DNA called? 

  Nucleotides
• What is an alternative name for a base?

  organic base or nitrogenous base
• There are four types of bases in DNA. What are their names?

  • Adenine
  • Thymine
  • Cytosine
  • Guanine
• Triplet


  Set of three bases
• Each set of three bases codes for a single

  Protein
• Chain of amino acids

  Polypeptide
• 1. The sequence of bases in DNA determines the sequence of amino acids in the chain.
  2. The chain of amino acids (a 'polypeptide'), then folds up to form a protein.
  3. Different sequences of amino acids lead to proteins with different shapes.
  4. This allows different proteins to carry out different functions.
• One function of proteins is to act as enzymes. What is the role of enzymes?

  To speed up the rate of chemical reactions
• One of the uses of proteins is to carry messages around the body. What do we call these proteins?

  Hormones
• Weak hydrogen bonds between bases hold two strands of DNA together.