DNA Replication “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material” ~Watson and Crick

Why do cells need DNA?  DNA contains the information cells need to function and live.

Why do cells need to replicate (copy) their DNA?  To make new cells

How do cells replicate their DNA? unwound by an enzyme. 1.The DNA double helix is

adds complementary nucleotides. 2.Another enzyme moves down the 2 original DNA strands and

3.Two separate DNA molecules are formed, each with one new strand and one old strand.

Replication Mistakes  6 billion base pairs per cell.  All are replicated in a few hours.  Mistake happens one per billion nucleotides.

Mistakes = Mutations  Mutations are changes in the base sequence of the DNA molecules.  This can have serious affects on genes and the functions of cells.  Cancer is caused by mutations in DNA.

Mutagens  Physical of chemical factor that increases the frequency of mutations.  Examples: UV rays, X- rays, smoking

3 Types of Mutations  Insertion  Deletion  Substitution