Nucleic Acids and Protein Synthesis Notes The primary function of DNA is to store and transmit genetic information that tells cells which proteins to make and when to make them.

The structure of DNA: DNA (deoxyribonucleic acid) is a nucleic acid. DNA is made up of repeating subunits called nucleotides. A nucleotide has three parts: a sugar molecule called deoxyribose a phosphate group a nitrogen-containing base

The four nitrogen-containing bases found in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). Adenine and guanine are purines because they have two rings of carbon. Cytosine and thymine are pyrimidines because they only have one ring of carbon.

Ja mes Watson and Francis Crick discovered the structure of DNA in 1953, called the double helix

Complementary base-pairing-DNA nucleotide pairing Cytosine binds with guanine. Adenine bonds with thymine. This pairing suggested how DNA replicates during interphase.

Replication of DNA Copying DNA in a cell is called replication. 1 st step-separation of two nucleotide chains (separate at the replication fork); the two chains are separated by enzyme called helicase (zipper)

2 nd step-DNA polymerases (also enzymes) bind to separated DNA chains and lay down a new chain of DNA; it also acts as a proofreader

Suppose A-T-T-C-C-G is the old sequence. What is the new sequence? 3 rd step-enzyme ligase seals the bonds between the nucleotides

rna2.swf ddna/ swf