Download 8.2 * 8.3 Notes

8.2 – 8.3
NOTES
Reaves
WHAT IS DNA?
Deoxyribonucleic acid is a
molecule that carries most of the
genetic instructions used in the
development, functioning and
reproduction of all known living
organisms and many viruses.
STRUCTURE OF DNA
DNA is composed of four types of nucleotides.
Nucleotides –
 The small units, or monomers, that make up DNA.
 Each nucleotide has three parts.
 A phosphate group.
 A ring-shaped sugar called deoxyribose.
 A nitrogen-containing base.
 The four types of nucleotides only differ in their nitrogen-
containing bases.
 One molecule of human
DNA contains billions of nucleotides.
STRUCTURE OF DNA
 P 230
STRUCTURE OF DNA
 Watson and Crick’s DNA model.
 double helix – two strands of DNA wind around each other like a twisted ladder
 The strands are complementary – they fit together and are the opposite of each other.
Chargaff’s Rules:
A = T
C = G

- DNA nucleotides of a single strand are joined

together by covalent bonds that connect the

sugar of one nucleotide to the phosphate of the

next nucleotide.
STRUCTURE OF DNA
DNA REPLICATION
 Replication copies the genetic information.
 Replication – the process by which DNA is copied during the cell cycle
 Which phase of the cell cycle does this occur?

assures that every cell has a complete set
of identical genetic information
DNA REPLICATION
 DNA only carries information.
 Enzymes and other proteins do all the work of replication.
 DNA polymerases –
 bond the new nucleotides together
Think Polident – bonds dentures to gums.
DNA REPLICATION PROCESS
 P 236 – Rewrite in your words.
DNA REPLICATION PROCESS
existing
molecule
two DNA
molecules
formed
unzipping
nucleotides
added
Read p 238