Structure of DNA

• DNA is a double-stranded helix held by complementary base pairs.

• The four bases make up the genetic code.
  • adenine (A)
  • cytosine (C)
  • guanine (G)
  • thymine (T)
• A is always paired with T and C is always paired with G.
• DNA carries the genetic information for making proteins.
• The base sequence determines amino acid sequence in proteins.

• A gene is a section of DNA which codes for a protein.

Production of Proteins

Messenger RNA (mRNA) is a molecule which carries a complementary copy of the genetic code from the DNA, in the nucleus, to a ribosome, where the protein is assembled from amino acids.

Topic Summary